Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utiliz...Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.展开更多
In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbo...In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.展开更多
Regulation with nitrogen and oxygen co-doping on growth and properties of boron doped diamond films is studied by using laughing gas as dopant. As the concentration of laughing gas(N2O/C) increases from 0 to 10%, the ...Regulation with nitrogen and oxygen co-doping on growth and properties of boron doped diamond films is studied by using laughing gas as dopant. As the concentration of laughing gas(N2O/C) increases from 0 to 10%, the growth rate of diamond film decreases gradually, and the nitrogen-vacancy(NV) center luminescence intensity increases first and then weakens. The results show that oxygen in laughing gas has a strong inhibitory effect on formation of NV centers, and the inhibitory effect would be stronger as the concentration of laughing gas increases. As a result, the film growth rate and nitrogen-related compensation donor decrease, beneficial to increase the acceptor concentration(~3.2×10^(19)cm^(-3)) in the film. Moreover, it is found that the optimal regulation with the quality and electrical properties of boron doped diamond films could be realized by adding appropriate laughing gas, especially the hole mobility(~700cm^(2)/V·s), which is beneficial to the realization of high-quality boron doped diamond films and high-level optoelectronic device applications in the future.展开更多
Photosynthesis is the most important biochemical reaction on Earth. It has co-evolved and developed with the Earth, driving the biogeochemical cycle of all elements on the planet and serving as the only chemical proce...Photosynthesis is the most important biochemical reaction on Earth. It has co-evolved and developed with the Earth, driving the biogeochemical cycle of all elements on the planet and serving as the only chemical process in nature that can convert light energy into chemical energy. Some heavy oxygen isotopic(^(18)O) labeling experiments have"conclusively" demonstrated that the oxygen released by photosynthesis comes only from water and are written into textbooks. However, it is not difficult to find that bicarbonate has never been excluded from the direct substrate of photosynthesis from beginning to end during the history of photosynthesis research. No convincing mechanism can be used to explain photosynthetic oxygen evolution solely from water photolysis. The bicarbonate effect, the Dole effect, the thermodynamic convenience of bicarbonate photolysis, the crystal structure characteristics of photosystem Ⅱ, and the reinterpretation of heavy oxygen isotopic labeling(^(18)O)experiments all indicate that the photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis. The recently proposed view that bicarbonate photolysis is the premise of water photolysis, bicarbonate photolysis and water photolysis work together with a 1:1(mol/mol) stoichiometric relationship, and the stoichiometric relationship between oxygen and carbon dioxide released during photosynthetic oxygen evolution is also 1:1, has excellent applicability and objectivity, which can logically and reasonably explain the precise coordination between light and dark reactions during photosynthesis, the bicarbonate effect, the Dole effect, the Kok cycle and the neutrality of water and carbon in nature.This is of great significance for constructing the bionic artificial photosynthetic reactors and scientifically answering the question of the source of elemental stoichiometric relationships in nature.展开更多
Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production...Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could provide oxygen from different sources(air,water,CO_(2),etc.),and they are more flexible in adapting to current processes,producing oxygen at 700^(-1)000℃.Furthermore,OTMs can be integrated into catalytic membrane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)),imposing different electric currents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface temperature and the associated O_(2) permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900℃on the surface,whereas the surrounding of the membrane was maintained at 650℃.The O_(2)permeation flux reached for the electrified membranes was~3.7 NmL min^(-1)cm^(-2),corresponding to the flux obtained with an OTM non-electrified at 900℃.The influence of depositing a porous Ce_(0.8)Tb_(0.2)O_(2-δ) catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temperature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O_(2) injection into the reaction can be easily fine-tuned.展开更多
The oxygen evolution reaction(OER)is a crucial step in metal-air batteries and water splitting technologies,playing a significant role in the efficiency and achievable heights of these two technologies.However,the OER...The oxygen evolution reaction(OER)is a crucial step in metal-air batteries and water splitting technologies,playing a significant role in the efficiency and achievable heights of these two technologies.However,the OER is a four-step,four-electron reaction,and its slow kinetics result in high overpotentials,posing a challenge.To address this issue,numerous strategies involving modified catalysts have been proposed and proven to be highly efficient.In these strategies,the introduction of strain has been widely reported because it is generally believed to effectively regulate the electronic structure of metal sites and alter the adsorption energy of catalyst surfaces with reaction intermediates.However,strain has many other effects that are not well known,making it an important yet unexplored area.Based on this,this review provides a detailed introduction to the various roles of strain in OER.To better explain these roles,the review also presents the definition of strain and elucidates the potential mechanisms of strain in OER based on the d-band center theory and adsorption volcano plot.Additionally,the review showcases various ways of introducing strain in OER through examples reported in the latest literature,aiming to provide a comprehensive perspective for the development of strain engineering.Finally,the review analyzes the appropriate proportion of strain introduction,compares compressive and tensile strain,and examines the impact of strain on stability.And the review offers prospects for future research directions in this emerging field.展开更多
The formation of multiple oxygen intermediates supporting efficient oxygen evolution reaction(OER)are affinitive with hydroxyl adsorption.However,ability of the catalyst to capture hydroxyl and maintain the continuous...The formation of multiple oxygen intermediates supporting efficient oxygen evolution reaction(OER)are affinitive with hydroxyl adsorption.However,ability of the catalyst to capture hydroxyl and maintain the continuous supply at active sits remains a tremendous challenge.Herein,an affordable Ni2P/FeP2 heterostructure is presented to form the internal polarization field(IPF),arising hydroxyl spillover(HOSo)during OER.Facilitated by IPF,the oriented HOSo from FeP2 to Ni2P can activate the Ni site with a new hydroxyl transmission channel and build the optimized reaction path of oxygen intermediates for lower adsorption energy,boosting the OER activity(242 mV vs.RHE at 100 mA cm-2)for least 100 h.More interestingly,for the anion exchange membrane water electrolyzer(AEMWE)with low concentration electrolyte,the advantage of HOSo effect is significantly amplified,delivering 1 A cm^(-2)at a low cell voltage of 1.88 V with excellent stability for over 50 h.展开更多
BACKGROUND Hepatorenal syndrome(HRS)is the most prevalent form of acute kidney injury in cirrhotic patients.It is characterized by reduced renal blood flow and represents the most severe complication in cirrhotic pati...BACKGROUND Hepatorenal syndrome(HRS)is the most prevalent form of acute kidney injury in cirrhotic patients.It is characterized by reduced renal blood flow and represents the most severe complication in cirrhotic patients with advanced disease.Previous research has indicated that antioxidants can delay the onset of a hyperdynamic circulatory state in cirrhosis and improve renal function in HRS patients.Regular omega-3 supplementation has significantly reduced the risk of liver disease.This supplementation could represent an additional therapy for individuals with HRS.AIM To evaluated the antioxidant effect of omega-3 polyunsaturated fatty acid supplementation on the kidneys of cirrhotic rats.METHODS Secondary biliary cirrhosis was induced in rats by biliary duct ligation(BDL)for 28 d.We used 24 male Wistar rats divided into the following groups:I(control);II(treated with omega-3,1 g/kg of body weight);III(BDL treated with omega-3,1 g/kg of body weight);and IV(BDL without treatment).The animals were killed by overdose of anesthetic;the kidneys were dissected,removed,frozen in liquid nitrogen,and stored in a freezer at-80℃for later analysis.We evaluated oxidative stress,nitric oxide(NO)metabolites,DNA damage by the comet assay,cell viability test,and apoptosis in the kidneys.Data were analyzed by one-way analysis of variance,and means were compared using the Tukey test,with P≤0.05.RESULTS Omega-3 significantly decreased the production of reactive oxygen species(P<0.001)and lipoperoxidation in the kidneys of cirrhotic rats treated with omega-3(P<0.001).The activity of the antioxidant enzymes superoxide dismutase and catalase increased in the BDL+omega-3 group compared to the BDL group(P<0.01).NO production,DNA damage,and caspase-9 cleavage decreased significantly in the omega-3-treated BDL group.There was an increase in mitochondrial electrochemical potential(P<0.001)in BDL treated with omega-3 compared to BDL.No changes in the cell survival index in HRS with omega-3 compared to the control group(P>0.05)were observed.CONCLUSION The study demonstrates that omega-3 can protect cellular integrity and function by increasing antioxidant enzymes,inhibiting the formation of free radicals,and reducing apoptosis.展开更多
Polytetrafluoroethylene (Teflon), a widely used spacecraft material, isstudied to investigate the vacuum ultraviolet (VUV) effects and its synergistic effects with atomicoxygen (AO) in a ground-based simulation facili...Polytetrafluoroethylene (Teflon), a widely used spacecraft material, isstudied to investigate the vacuum ultraviolet (VUV) effects and its synergistic effects with atomicoxygen (AO) in a ground-based simulation facility. The samples before and after the experiments arecompared in appearance, mass, optical properties and surface composition. The reactioncharacteristics of Teflon are summarized and the reaction mechanisms are analyzed. The followingconclusion can be drawn: at the action of VUV the Teflon sample surface is darkened for theaccumulation of carbon; and when the sample is exposed to AO, the carbon is oxidized and thedarkening surface is bleached; the synergistic effects of VUV and AO may cause the erosion of Teflonmore severe.展开更多
The most energy-inefficient step in the oxygen evolution reaction(OER), which involves a complicated four-electron transfer process, limits the efficiency of the electrochemical water splitting. Here, well-defined Ni/...The most energy-inefficient step in the oxygen evolution reaction(OER), which involves a complicated four-electron transfer process, limits the efficiency of the electrochemical water splitting. Here, well-defined Ni/Co3O4 nanoparticles coupled with N-doped carbon hybrids(Ni/Co3O4@NC) were synthesized via a facile impregnation-calcination method as efficient electrocatalysts for OER in alkaline media. Notably, the impregnation of the polymer with Ni and Co ions in the first step ensured the homogeneous distribution of metals, thus guaranteeing the subsequent in situ calcination reaction, which produced well-dispersed Ni and Co3O4 nanoparticles. Moreover, the N-doped carbon matrix formed at high temperatures could effectively prevent the aggregation and coalescence, and regulate the electronic configuration of active species. Benefiting from the synergistic effect between the Ni, Co3O4, and NC species, the obtained Ni/Co3O4@NC hybrids exhibited enhanced OER activities and remarkable stability in an alkaline solution with a smaller overpotential of 350 m V to afford 10 m A cm-2, lower Tafel slope of 52.27 m V dec-1, smaller charge-transfer resistance, and higher double-layer capacitance of 25.53 m F cm-2 compared to those of unary Co3O4@NC or Ni@NC metal hybrids. Therefore, this paper presents a facile strategy for designing other heteroatom-doped oxides coupled with ideal carbon materials as electrocatalysts for the OER.展开更多
Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the opt...Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the optical transmission as high as 94% are easily attained by postdeposition annealing treatment. The effects of oxygen concentration in the reactive gas mixture and post-deposition annealing treatment on the optical transmittance as well as optical parameters, such as refractive index (n), extinction coefficient (k), real part (ε') and imaginary part (ε') of the dielectric constant, were studied in the visible and near-infrared region. The highfrequency dielectric constant ε∞ the plasma frequency ωP, and the conduction band effective mass mc of different samples were also investigated展开更多
As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline o...As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs)in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively)of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,IOMZ,is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ.With higher IOMZ,the degradation of particulate organic carbon(POC)tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.展开更多
The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases fr...The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (Or) within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.展开更多
Dealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst.Here...Dealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst.Herein,to address the deficiencies associated with the commonly used dealloying methods,for example,electrochemical and sulfuric acid/nitric acid treatment,we report an acetic acid-assisted mild strategy to dealloy Cu atoms from the outer surface layers of CuPd alloy nanoparticles to achieve high-efficiency electrocatalysis for oxygen reduction and ethanol oxidation in an alkaline electrolyte.The leaching of Cu atoms by acetic acid exerts an additional compressive strain effect on the surface layers and exposes more active Pd atoms,which is beneficial for boosting the catalytic performance of a dealloyed catalyst for the oxygen reduction reaction(ORR)and the ethanol oxidation reaction(EOR).In particular,for ORR,the CuPd nanoparticles with a Pd/Cu molar ratio of 2:1 after acetic dealloying show a half-wave potential of 0.912 V(vs.RHE)and a mass activity of 0.213 AmgPd^(-1) at 0.9 V,respectively,while for EOR,the same dealloyed sample has a mass activity and a specific activity of 8.4 Amg^(-1) and 8.23 mA cm^(-2),respectively,much better than their dealloyed counterparts at other temperatures and commercial Pd/C as well as a Pt/C catalyst.展开更多
Co-N-C is a promising oxygen electrochemical catalyst due to its high stability and good durability.However,due to the limited adsorption ability improvement for oxygen-containing intermediates,it usually exhibits ina...Co-N-C is a promising oxygen electrochemical catalyst due to its high stability and good durability.However,due to the limited adsorption ability improvement for oxygen-containing intermediates,it usually exhibits inadequate catalytic activity with 2-electron pathway and high selectivity of hydrogen peroxide.Herein,the adsorption of Co-N-C to these intermediates is modulated by constructing heterostructures using transition metals and their derivatives based on d-band theory.The heterostructured nanobelts with MoC core and pomegranate-like carbon shell consisting of Co nanoparticles and N dopant(MoC/Co-N-C)are engineered to successfully modulate the d band center of active Co-N-C sites,resulting in a remarkably enhanced electrocatalysis performance.The optimally performing MoC/Co-N-C exhibits outstanding bi-catalytic activity and stability for the oxygen electrochemistry,featuring a high wave-half potential of 0.865 V for the oxygen reduction reaction(ORR)and low overpotential of 370 mV for the oxygen evolution reaction(OER)at 10 mA cm^(-2).The zinc air batteries with the MoC/Co-N-C catalyst demonstrate a large power density of 180 mW cm^(-2)and a long cycling lifespan(2000 cycles).The density functional theory calculations with Hubbard correction(DFT+U)reveal the electron transferring from Co to Mo atoms that effectively modulate the d band center of the active Co sites and achieve optimum adsorption ability with"single site double adsorption"mode.展开更多
The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining tre...The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining treatment. Thp result shows that K-e is equal to 1.2 which is an important parameter for floating zone refining terbium.展开更多
Electrocatalytic oxygen reduction and evolution reactions are involved in new energy conversion and storage technologies,such as various fuel cells and metal-air batteries and also water splitting devices[1,2].However...Electrocatalytic oxygen reduction and evolution reactions are involved in new energy conversion and storage technologies,such as various fuel cells and metal-air batteries and also water splitting devices[1,2].However,both reactions are very slow in kinetics,and thus catalysts are required[3,4].展开更多
Objective:To investigate the effect of hyperbaric oxygen (HBO) on serum inflammatory factors, oxidative stress status, endothelial cell function and intracranial pressure in patients with severe craniocerebral injury ...Objective:To investigate the effect of hyperbaric oxygen (HBO) on serum inflammatory factors, oxidative stress status, endothelial cell function and intracranial pressure in patients with severe craniocerebral injury (STBI), and to provide scientific basis for clinical treatment of patients with severe craniocerebral injury.Methods: 110 cases of STBI were selected and divided into control group and treatment group according to the random data table, 55 cases in each group. The control group received conventional combined therapy, the observation group were given HBO treatment on the base of the control group, the inflammatory factors [C reactive protein (CRP), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10)] and oxidative stress [malondialdehyde (MDA) and superoxide dismutase-1 (SOD-1)], endothelin (ET) and intracranial pressure (ICP) level changes of the two groups were observed and compared before and after treatment for 10 d in patients. Results: The levels of CRP, TNF-α, IL-6, MDA, ET and ICP in the treatment group and the control group were significantly lower than those in the same group before treatment, the difference was statistically significant (P<0.05), the CRP, TNF-α, IL-6, MDA, ET and ICP levels of the observation group after treatment were significantly lower than the control group after treatment (P<0.05);After treatment, IL-10 and SOD-1 levels of the two groups of patients were significantly increased than the same group before treatment (P<0.05), and both levels in the observation group after treatment was significantly higher than the control group after treatment (P<0.05).Conclusions: HBO treatment of severe brain injury patients with significant effect, can effectively reduce oxidative stress damage and inflammation, improve patients' endothelial cell function, reduce intracranial pressure, and has a certain clinical value.展开更多
One of the primary challenges in relation to phosphoric acid fuel cells is catalyst poisoning by phosphate anions that occurs at the interface between metal nanoparticles and the electrolyte.The strong adsorption of p...One of the primary challenges in relation to phosphoric acid fuel cells is catalyst poisoning by phosphate anions that occurs at the interface between metal nanoparticles and the electrolyte.The strong adsorption of phosphate anions on the catalyst surface limits the active sites for the oxygen reduction reaction(ORR),significantly deteriorating fuel cell performance.Here,antipoisoning catalysts consisting of Pt-based nanoparticles encapsulated in an ultrathin carbon shell that can be used as a molecular sieve layer are rationally designed.The pore structure of the carbon shells is systematically regulated at the atomic level by high-temperature gas treatment,allowing O_(2) molecules to selectively react on the active sites of the metal nanoparticles through the molecular sieves.Besides,the carbon shell,as a protective layer,effectively prevents metal dissolution from the catalyst during a long-term operation.Consequently,the defect-controlled carbon shell leads to outstanding ORR activity and durability of the hybrid catalyst even in phosphoric acid electrolytes.展开更多
Effect of oxygen addition on diamond film deposition at higher pressure was studied.It was found that addition of oxygen suppressed diamond nucleation,and the effect of suppression increased with increasing pressure,a...Effect of oxygen addition on diamond film deposition at higher pressure was studied.It was found that addition of oxygen suppressed diamond nucleation,and the effect of suppression increased with increasing pressure,and at certain pressure level diamond deposition was completely prohibited.Etching effect due to oxygen addition dominated at the very early stage(nucleation stage),therefore it is still possible to take the advantage of oxygen addition on quality improvement of diamond films by introducing oxygen after the nucleation stage.展开更多
基金supported by the National Natural Science Foundation of China(22234005,21974070)the Natural Science Foundation of Jiangsu Province(BK20222015)。
文摘Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.
基金supported by the National Natural Science Foundation of China(21972131)。
文摘In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2018YFB0406502, 2017YFF0210800, and 2017YFB0403003)the National Natural Science Foundation of China (Grant Nos. 61974059, 61674077, and 61774081)+1 种基金the Natural Science Foundation of Jiangsu Province (Grant No. BK20160065)the Fundamental Research Funds for the Central Universities。
文摘Regulation with nitrogen and oxygen co-doping on growth and properties of boron doped diamond films is studied by using laughing gas as dopant. As the concentration of laughing gas(N2O/C) increases from 0 to 10%, the growth rate of diamond film decreases gradually, and the nitrogen-vacancy(NV) center luminescence intensity increases first and then weakens. The results show that oxygen in laughing gas has a strong inhibitory effect on formation of NV centers, and the inhibitory effect would be stronger as the concentration of laughing gas increases. As a result, the film growth rate and nitrogen-related compensation donor decrease, beneficial to increase the acceptor concentration(~3.2×10^(19)cm^(-3)) in the film. Moreover, it is found that the optimal regulation with the quality and electrical properties of boron doped diamond films could be realized by adding appropriate laughing gas, especially the hole mobility(~700cm^(2)/V·s), which is beneficial to the realization of high-quality boron doped diamond films and high-level optoelectronic device applications in the future.
基金the Support Plan Projects of Science and Technology Department of Guizhou Province [No.(2021)YB453]。
文摘Photosynthesis is the most important biochemical reaction on Earth. It has co-evolved and developed with the Earth, driving the biogeochemical cycle of all elements on the planet and serving as the only chemical process in nature that can convert light energy into chemical energy. Some heavy oxygen isotopic(^(18)O) labeling experiments have"conclusively" demonstrated that the oxygen released by photosynthesis comes only from water and are written into textbooks. However, it is not difficult to find that bicarbonate has never been excluded from the direct substrate of photosynthesis from beginning to end during the history of photosynthesis research. No convincing mechanism can be used to explain photosynthetic oxygen evolution solely from water photolysis. The bicarbonate effect, the Dole effect, the thermodynamic convenience of bicarbonate photolysis, the crystal structure characteristics of photosystem Ⅱ, and the reinterpretation of heavy oxygen isotopic labeling(^(18)O)experiments all indicate that the photosynthetic oxygen evolution does not exclude the important role and contribution of bicarbonate photolysis. The recently proposed view that bicarbonate photolysis is the premise of water photolysis, bicarbonate photolysis and water photolysis work together with a 1:1(mol/mol) stoichiometric relationship, and the stoichiometric relationship between oxygen and carbon dioxide released during photosynthetic oxygen evolution is also 1:1, has excellent applicability and objectivity, which can logically and reasonably explain the precise coordination between light and dark reactions during photosynthesis, the bicarbonate effect, the Dole effect, the Kok cycle and the neutrality of water and carbon in nature.This is of great significance for constructing the bionic artificial photosynthetic reactors and scientifically answering the question of the source of elemental stoichiometric relationships in nature.
基金Financial support by the Spanish Ministry of Science(PID2022139663OB-I00 and CEX2021-001230-S grant funded by MCIN/AE I/10.13039/501100011033)with funding from Next Generation EU(PRTR-C17.I1)within the Planes Complementarios con CCAA(Area of Green Hydrogen and Energy)+2 种基金carried out in the CSIC Interdisciplinary Thematic Platform(PTI+)Transición Energética Sostenible+(PTI-TRANSENER+)the Universitat Politècnica de València(UPV)the support of the Servicio de Microscopía Elcectronica of the UPV。
文摘Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could provide oxygen from different sources(air,water,CO_(2),etc.),and they are more flexible in adapting to current processes,producing oxygen at 700^(-1)000℃.Furthermore,OTMs can be integrated into catalytic membrane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)),imposing different electric currents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface temperature and the associated O_(2) permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900℃on the surface,whereas the surrounding of the membrane was maintained at 650℃.The O_(2)permeation flux reached for the electrified membranes was~3.7 NmL min^(-1)cm^(-2),corresponding to the flux obtained with an OTM non-electrified at 900℃.The influence of depositing a porous Ce_(0.8)Tb_(0.2)O_(2-δ) catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temperature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O_(2) injection into the reaction can be easily fine-tuned.
基金financially supported by the National Natural Science Foundation of China(52071072)the Fundamental Research Funds for the Central Universities(2023GFZD03)+4 种基金the Natural Science Foundation-Steel,the Iron Foundation of Hebei Province(E2022501030)the Key Research and Development Plan of Qinhuangdao City(202302B013)the Liaoning Applied Basic Research Program(2023JH2/101300011)the Basic scientific research project of Liaoning Province Department of Education(LJKZZ20220024)the Shenyang Science and Technology Project(23-407-3-13)。
文摘The oxygen evolution reaction(OER)is a crucial step in metal-air batteries and water splitting technologies,playing a significant role in the efficiency and achievable heights of these two technologies.However,the OER is a four-step,four-electron reaction,and its slow kinetics result in high overpotentials,posing a challenge.To address this issue,numerous strategies involving modified catalysts have been proposed and proven to be highly efficient.In these strategies,the introduction of strain has been widely reported because it is generally believed to effectively regulate the electronic structure of metal sites and alter the adsorption energy of catalyst surfaces with reaction intermediates.However,strain has many other effects that are not well known,making it an important yet unexplored area.Based on this,this review provides a detailed introduction to the various roles of strain in OER.To better explain these roles,the review also presents the definition of strain and elucidates the potential mechanisms of strain in OER based on the d-band center theory and adsorption volcano plot.Additionally,the review showcases various ways of introducing strain in OER through examples reported in the latest literature,aiming to provide a comprehensive perspective for the development of strain engineering.Finally,the review analyzes the appropriate proportion of strain introduction,compares compressive and tensile strain,and examines the impact of strain on stability.And the review offers prospects for future research directions in this emerging field.
基金This work is financially supported by National Natural Science Foundation of China(52174283 and 52274308)Innovation Fund Project for Graduate Student of China University of Petroleum(East China)(22CX04023A)the Fundamental Research Funds for the Central Universities。
文摘The formation of multiple oxygen intermediates supporting efficient oxygen evolution reaction(OER)are affinitive with hydroxyl adsorption.However,ability of the catalyst to capture hydroxyl and maintain the continuous supply at active sits remains a tremendous challenge.Herein,an affordable Ni2P/FeP2 heterostructure is presented to form the internal polarization field(IPF),arising hydroxyl spillover(HOSo)during OER.Facilitated by IPF,the oriented HOSo from FeP2 to Ni2P can activate the Ni site with a new hydroxyl transmission channel and build the optimized reaction path of oxygen intermediates for lower adsorption energy,boosting the OER activity(242 mV vs.RHE at 100 mA cm-2)for least 100 h.More interestingly,for the anion exchange membrane water electrolyzer(AEMWE)with low concentration electrolyte,the advantage of HOSo effect is significantly amplified,delivering 1 A cm^(-2)at a low cell voltage of 1.88 V with excellent stability for over 50 h.
基金Supported by Brazilian Agencies:Conselho Nacional de Desenvolvimento Científico e TecnológicoPrograma Nacional de Cooperação Acadêmica/Coordenação de Aperfeiçoamento de Pessoal de Nível Superiorand Fundação de AmparoàPesquisa do Estado do Rio Grande do Sul.
文摘BACKGROUND Hepatorenal syndrome(HRS)is the most prevalent form of acute kidney injury in cirrhotic patients.It is characterized by reduced renal blood flow and represents the most severe complication in cirrhotic patients with advanced disease.Previous research has indicated that antioxidants can delay the onset of a hyperdynamic circulatory state in cirrhosis and improve renal function in HRS patients.Regular omega-3 supplementation has significantly reduced the risk of liver disease.This supplementation could represent an additional therapy for individuals with HRS.AIM To evaluated the antioxidant effect of omega-3 polyunsaturated fatty acid supplementation on the kidneys of cirrhotic rats.METHODS Secondary biliary cirrhosis was induced in rats by biliary duct ligation(BDL)for 28 d.We used 24 male Wistar rats divided into the following groups:I(control);II(treated with omega-3,1 g/kg of body weight);III(BDL treated with omega-3,1 g/kg of body weight);and IV(BDL without treatment).The animals were killed by overdose of anesthetic;the kidneys were dissected,removed,frozen in liquid nitrogen,and stored in a freezer at-80℃for later analysis.We evaluated oxidative stress,nitric oxide(NO)metabolites,DNA damage by the comet assay,cell viability test,and apoptosis in the kidneys.Data were analyzed by one-way analysis of variance,and means were compared using the Tukey test,with P≤0.05.RESULTS Omega-3 significantly decreased the production of reactive oxygen species(P<0.001)and lipoperoxidation in the kidneys of cirrhotic rats treated with omega-3(P<0.001).The activity of the antioxidant enzymes superoxide dismutase and catalase increased in the BDL+omega-3 group compared to the BDL group(P<0.01).NO production,DNA damage,and caspase-9 cleavage decreased significantly in the omega-3-treated BDL group.There was an increase in mitochondrial electrochemical potential(P<0.001)in BDL treated with omega-3 compared to BDL.No changes in the cell survival index in HRS with omega-3 compared to the control group(P>0.05)were observed.CONCLUSION The study demonstrates that omega-3 can protect cellular integrity and function by increasing antioxidant enzymes,inhibiting the formation of free radicals,and reducing apoptosis.
文摘Polytetrafluoroethylene (Teflon), a widely used spacecraft material, isstudied to investigate the vacuum ultraviolet (VUV) effects and its synergistic effects with atomicoxygen (AO) in a ground-based simulation facility. The samples before and after the experiments arecompared in appearance, mass, optical properties and surface composition. The reactioncharacteristics of Teflon are summarized and the reaction mechanisms are analyzed. The followingconclusion can be drawn: at the action of VUV the Teflon sample surface is darkened for theaccumulation of carbon; and when the sample is exposed to AO, the carbon is oxidized and thedarkening surface is bleached; the synergistic effects of VUV and AO may cause the erosion of Teflonmore severe.
文摘The most energy-inefficient step in the oxygen evolution reaction(OER), which involves a complicated four-electron transfer process, limits the efficiency of the electrochemical water splitting. Here, well-defined Ni/Co3O4 nanoparticles coupled with N-doped carbon hybrids(Ni/Co3O4@NC) were synthesized via a facile impregnation-calcination method as efficient electrocatalysts for OER in alkaline media. Notably, the impregnation of the polymer with Ni and Co ions in the first step ensured the homogeneous distribution of metals, thus guaranteeing the subsequent in situ calcination reaction, which produced well-dispersed Ni and Co3O4 nanoparticles. Moreover, the N-doped carbon matrix formed at high temperatures could effectively prevent the aggregation and coalescence, and regulate the electronic configuration of active species. Benefiting from the synergistic effect between the Ni, Co3O4, and NC species, the obtained Ni/Co3O4@NC hybrids exhibited enhanced OER activities and remarkable stability in an alkaline solution with a smaller overpotential of 350 m V to afford 10 m A cm-2, lower Tafel slope of 52.27 m V dec-1, smaller charge-transfer resistance, and higher double-layer capacitance of 25.53 m F cm-2 compared to those of unary Co3O4@NC or Ni@NC metal hybrids. Therefore, this paper presents a facile strategy for designing other heteroatom-doped oxides coupled with ideal carbon materials as electrocatalysts for the OER.
文摘Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the optical transmission as high as 94% are easily attained by postdeposition annealing treatment. The effects of oxygen concentration in the reactive gas mixture and post-deposition annealing treatment on the optical transmittance as well as optical parameters, such as refractive index (n), extinction coefficient (k), real part (ε') and imaginary part (ε') of the dielectric constant, were studied in the visible and near-infrared region. The highfrequency dielectric constant ε∞ the plasma frequency ωP, and the conduction band effective mass mc of different samples were also investigated
基金the Science&Technology Basic Resources Investigation Program of China(No.2017FY100802)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19060401)the National Natural Science Foundation of China(No.91958103)。
文摘As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO)content of the world’s oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs)in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively)of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,IOMZ,is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is Kocebu>M2>Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using IOMZ.With higher IOMZ,the degradation of particulate organic carbon(POC)tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB327504,2011CB922100 and2011CB301900the National Natural Science Foundation of China under Grant Nos 11104130 and 61322112+2 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011556 and BK2011050the Priority Academic Program Development of Jiangsu Higher Education Institutionsand the NUPTSF Grant Nos NY213069 and NY214028
文摘The effect of oxygen partial pressure (Po2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As Po2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (Or) within the a-IGZO layer is suppressed by increasing Po2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing Po2. Therefore, the improved interface quality with increasing Po2 during the channel layer deposition can be attributed to the reduction of interface Ov-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.
基金the financial support provided by the National Natural Science Foundation of China(22075290,21972068,52164028)the Beijing Natural Science Foundation(Z200012)+3 种基金the State Key Laboratory of Multiphase Complex Systemsthe Institute of Process Engineeringthe Chinese Academy of Sciences(MPCS-2021-A-05)the Nanjing IPE Institute of Green Manufacturing Industry(E0010725).
文摘Dealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst.Herein,to address the deficiencies associated with the commonly used dealloying methods,for example,electrochemical and sulfuric acid/nitric acid treatment,we report an acetic acid-assisted mild strategy to dealloy Cu atoms from the outer surface layers of CuPd alloy nanoparticles to achieve high-efficiency electrocatalysis for oxygen reduction and ethanol oxidation in an alkaline electrolyte.The leaching of Cu atoms by acetic acid exerts an additional compressive strain effect on the surface layers and exposes more active Pd atoms,which is beneficial for boosting the catalytic performance of a dealloyed catalyst for the oxygen reduction reaction(ORR)and the ethanol oxidation reaction(EOR).In particular,for ORR,the CuPd nanoparticles with a Pd/Cu molar ratio of 2:1 after acetic dealloying show a half-wave potential of 0.912 V(vs.RHE)and a mass activity of 0.213 AmgPd^(-1) at 0.9 V,respectively,while for EOR,the same dealloyed sample has a mass activity and a specific activity of 8.4 Amg^(-1) and 8.23 mA cm^(-2),respectively,much better than their dealloyed counterparts at other temperatures and commercial Pd/C as well as a Pt/C catalyst.
基金financially supported by the National Natural Science Foundation of China(No.21975163)the Shenzhen Innovative Research Team Program(KQTD20190929173914967)the Senior Talent Research Start-up Fund of Shenzhen University(000265)。
文摘Co-N-C is a promising oxygen electrochemical catalyst due to its high stability and good durability.However,due to the limited adsorption ability improvement for oxygen-containing intermediates,it usually exhibits inadequate catalytic activity with 2-electron pathway and high selectivity of hydrogen peroxide.Herein,the adsorption of Co-N-C to these intermediates is modulated by constructing heterostructures using transition metals and their derivatives based on d-band theory.The heterostructured nanobelts with MoC core and pomegranate-like carbon shell consisting of Co nanoparticles and N dopant(MoC/Co-N-C)are engineered to successfully modulate the d band center of active Co-N-C sites,resulting in a remarkably enhanced electrocatalysis performance.The optimally performing MoC/Co-N-C exhibits outstanding bi-catalytic activity and stability for the oxygen electrochemistry,featuring a high wave-half potential of 0.865 V for the oxygen reduction reaction(ORR)and low overpotential of 370 mV for the oxygen evolution reaction(OER)at 10 mA cm^(-2).The zinc air batteries with the MoC/Co-N-C catalyst demonstrate a large power density of 180 mW cm^(-2)and a long cycling lifespan(2000 cycles).The density functional theory calculations with Hubbard correction(DFT+U)reveal the electron transferring from Co to Mo atoms that effectively modulate the d band center of the active Co sites and achieve optimum adsorption ability with"single site double adsorption"mode.
文摘The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining treatment. Thp result shows that K-e is equal to 1.2 which is an important parameter for floating zone refining terbium.
基金the support from the National Natural Science Foundation of China(21773146,22171176 and 22102092)the Fok Ying-Tong Education Foundation for Outstanding Young Teachers in University+2 种基金the Research Funds of Shaanxi Normal Universitythe Fundamental Research Funds for the Central Universitiesthe NRF of Korea(NRF-2021R1A3B1076539 and NRF-2020R1I1A1A01074630)。
文摘Electrocatalytic oxygen reduction and evolution reactions are involved in new energy conversion and storage technologies,such as various fuel cells and metal-air batteries and also water splitting devices[1,2].However,both reactions are very slow in kinetics,and thus catalysts are required[3,4].
文摘Objective:To investigate the effect of hyperbaric oxygen (HBO) on serum inflammatory factors, oxidative stress status, endothelial cell function and intracranial pressure in patients with severe craniocerebral injury (STBI), and to provide scientific basis for clinical treatment of patients with severe craniocerebral injury.Methods: 110 cases of STBI were selected and divided into control group and treatment group according to the random data table, 55 cases in each group. The control group received conventional combined therapy, the observation group were given HBO treatment on the base of the control group, the inflammatory factors [C reactive protein (CRP), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10)] and oxidative stress [malondialdehyde (MDA) and superoxide dismutase-1 (SOD-1)], endothelin (ET) and intracranial pressure (ICP) level changes of the two groups were observed and compared before and after treatment for 10 d in patients. Results: The levels of CRP, TNF-α, IL-6, MDA, ET and ICP in the treatment group and the control group were significantly lower than those in the same group before treatment, the difference was statistically significant (P<0.05), the CRP, TNF-α, IL-6, MDA, ET and ICP levels of the observation group after treatment were significantly lower than the control group after treatment (P<0.05);After treatment, IL-10 and SOD-1 levels of the two groups of patients were significantly increased than the same group before treatment (P<0.05), and both levels in the observation group after treatment was significantly higher than the control group after treatment (P<0.05).Conclusions: HBO treatment of severe brain injury patients with significant effect, can effectively reduce oxidative stress damage and inflammation, improve patients' endothelial cell function, reduce intracranial pressure, and has a certain clinical value.
基金National Research Foundation of Korea(NRF),Grant/Award Number:2021R1A2C2012685Korea Institute of Energy Technology Evaluation and Planning(KETEP),Grant/Award Number:20203020030010Ministry of Trade,Industry&Energy(MOTIE,Korea),Grant/Award Number:20020400。
文摘One of the primary challenges in relation to phosphoric acid fuel cells is catalyst poisoning by phosphate anions that occurs at the interface between metal nanoparticles and the electrolyte.The strong adsorption of phosphate anions on the catalyst surface limits the active sites for the oxygen reduction reaction(ORR),significantly deteriorating fuel cell performance.Here,antipoisoning catalysts consisting of Pt-based nanoparticles encapsulated in an ultrathin carbon shell that can be used as a molecular sieve layer are rationally designed.The pore structure of the carbon shells is systematically regulated at the atomic level by high-temperature gas treatment,allowing O_(2) molecules to selectively react on the active sites of the metal nanoparticles through the molecular sieves.Besides,the carbon shell,as a protective layer,effectively prevents metal dissolution from the catalyst during a long-term operation.Consequently,the defect-controlled carbon shell leads to outstanding ORR activity and durability of the hybrid catalyst even in phosphoric acid electrolytes.
文摘Effect of oxygen addition on diamond film deposition at higher pressure was studied.It was found that addition of oxygen suppressed diamond nucleation,and the effect of suppression increased with increasing pressure,and at certain pressure level diamond deposition was completely prohibited.Etching effect due to oxygen addition dominated at the very early stage(nucleation stage),therefore it is still possible to take the advantage of oxygen addition on quality improvement of diamond films by introducing oxygen after the nucleation stage.