In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd...In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd/carbon nanosphere(CNS),obtained via immobilization of ultrafine Pd nanoparticles onto CNS,are developed and employed for both selective H_(2)generation from HCOOH dehydrogenation and O_(2)evolution from H_(2)O_(2)decomposition.In these reactions,the highest activities for Pd/CNS-800(i.e.,calcinated at 800℃)are 2478 h−1 and 993 min^(−1)for H_(2)and O_(2)evolution,respectively.The highly efficient and selective“on-off”switch for selective H_(2)generation from HCOOH is successfully realized by pH adjustment.This novel and highly efficient nanocatalyst Pd/CNS-800 not only provides new approaches for the promising application of HCOOH and H_(2)O_(2)as economic and safe H_(2)and O_(2)carriers,respectively,for fuel cells,but also promotes the development of“on-off”switch for on-demand H_(2)evolution.展开更多
The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O...The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B_(2)O_(3)(or B(OH)_(3)).By adding small amounts of B_(2)O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B_(2)O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl_(2) in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl_(2) solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B_(2)O_(3) and recycling the 0.5 M MgCl_(2) solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.展开更多
The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(MF)is very vital due to its existen...The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(MF)is very vital due to its existence in various sectors of industry and engineering.The present research focuses on mathematical modeling to simulate the cooling of a hot component through power-law(PL)nanofluid convection flow.The temperature reduction of the hot component inside a two-dimensional(2D)inclined chamber with two different cold wall shapes is evaluated.The formulation of the problem is derived with the lattice Boltzmann method(LBM)by code writing via the FORTRAN language.The variables such as the radiation parameter(0–1),the Hartmann number(0–75),the heat absorption/generation coefficient(−5–5),the fluid behavioral index(0.8–1.2),the Rayleigh number(103–105),the imposed MF angle(0°–90°),the chamber inclination angle(−90°–90°),and the cavity cold wall shape(smooth and curved)are investigated.The findings indicate that the presence of radiation increases the mean Nusselt number value for the shear-thickening,Newtonian,and shear thinning fluids by about 6.2%,4%,and 2%,respectively.In most cases,the presence of nanoparticles improves the heat transfer(HT)rate,especially in the cases where thermal conduction dominates convection.There is the lowest cooling performance index and MF effect for the cavity placed at an angle of 90°.The application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research.展开更多
Objective: To explore the protective effect of camellia oil against H2O2-induced oxidative stress injury in rat H9C2 cardiomyocytes. Methods: CCK8 method was used to detect the cell survival rate of H9C2 cardiomyocyte...Objective: To explore the protective effect of camellia oil against H2O2-induced oxidative stress injury in rat H9C2 cardiomyocytes. Methods: CCK8 method was used to detect the cell survival rate of H9C2 cardiomyocytes treated with different concentrations of H2O2. Normal cultured cells were used as the blank control group, and the cells were treated with 200 μmol/L H2O2 for 24 h. An oxidative stress injury model was constructed as the model group. The cells were pretreated with 1%, 0.1% and 0.01% camellia oil for 24 h, and then H2O2 was added for 24 h as the experimental group. The β-galactosidase senescence staining assay, mitochondrial membrane potential assay, EdU cell proliferation staining assay and scratch assay were used to observe the changes of cell senescence, mitochondrial membrane potential, proliferation, apoptosis and migration in each group. The superoxide dismutase (SOD) activity, lactate dehydrogenase (LDH) activity, and malondialdehyde (MDA) content of the cells in each group were detected by using the kit. Results: The cell viability of H9C2 cardiomyocytes treated with different concentrations of H2O2 was inhibited and positively correlated with the concentration of H2O2 (P<0.01). Compared with the blank control group, the positive rate of cell senescence, MDA content and LDH activity increased in the H2O2 model group (P<0.01);mitochondrial membrane potential, cellular value-added rate, migration rate and SOD activity decreased (P<0.01). Compared with the H2O2 model group, the positive rate of cellular senescence (P<0.01 or P<0.05), MDA content and LDH activity decreased (P< 0.01 or P<0.05);mitochondrial membrane potential increased, cell proliferation rate and migration rate increased (P<0.01 or P<0.05) in the experimental group. Conclusion: Camellia oil can significantly inhibit oxidative stress injury in H9C2 cells and exert cardiomyocyte protective effects.展开更多
Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified ...Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.展开更多
Photocatalytic water splitting is a promising method for hydrogen production.Numerous efficient photocatalysts have been synthesized and utilized.However,photocatalysts without a noble metal as the co-catalyst have be...Photocatalytic water splitting is a promising method for hydrogen production.Numerous efficient photocatalysts have been synthesized and utilized.However,photocatalysts without a noble metal as the co-catalyst have been rarely reported.Herein,a CoP co-catalyst-modified graphitic-C3N4(g-C3N4/CoP)is investigated for photocatalytic water splitting to produce H2.The g-C3N4/CoP composite is synthesized in two steps.The first step is related to thermal decomposition,and the second step involves an electroless plating technique.The photocatalytic activity for hydrogen evolution reactions of g-C3N4 is distinctly increased by loading the appropriate amount of CoP quantum dots(QDs).Among the as-synthesized samples,the optimized one(g-C3N4/CoP-4%)shows exceptional photocatalytic activity as compared with pristine g-C3N4,generating H2 at a rate of 936μmol g^-1 h^-1,even higher than that of g-C3N4 with 4 wt%Pt(665μmol g^-1 h^-1).The UV-visible and optical absorption behavior confirms that g-C3N4 has an absorption edge at 451 nm,but after being composited with CoP,g-C3N4/CoP-4%has an absorption edge at 497 nm.Furthermore,photoluminescence and photocurrent measurements confirm that loading CoP QDs to pristine g-C3N4 not only enhances the charge separation,but also improves the transfer of photogenerated e--h+pairs,thus improving the photocatalytic performance of the catalyst to generate H2.This work demonstrates a feasible strategy for the synthesis of highly efficient metal phosphide-loaded g-C3N4 for hydrogen generation.展开更多
Extended light absorption and dynamic charge separation are vital factors that determine the effectivenessof photocatalysts.In this study,a nonmetallic plasmonic S‐scheme photocatalyst was fabricatedby loading 1D pla...Extended light absorption and dynamic charge separation are vital factors that determine the effectivenessof photocatalysts.In this study,a nonmetallic plasmonic S‐scheme photocatalyst was fabricatedby loading 1D plasmonic W_(18)O_(49)nanowires onto 2D g‐C_(3)N_(4)nanosheets.W_(18)O_(49)nanowiresplay the dual role of a light absorption antenna—that extends light adsorption—and a hot electrondonor—that assists the water reduction reaction in a wider light spectrum range.Moreover,S‐scheme charge transfer resulting from the matching bandgaps of W_(18)O_(49)and g‐C_(3)N_(4)can lead tostrong redox capability and high migration speed of the photoinduced charges.Consequently,in thisstudy,W_(18)O_(49)/g‐C_(3)N_(4)hybrids exhibited higher photocatalytic H2 generation than that of pristineg‐C_(3)N_(4)under light irradiation of 420–550 nm.Furthermore,the H2 production rate of thebest‐performing W_(18)O_(49)/g‐C_(3)N_(4)hybrid was 41.5μmol·g^(−1)·h^(−1)upon exposure to monochromaticlight at 550 nm,whereas pure g‐C_(3)N_(4)showed negligible activity.This study promotes novel andenvironmentally friendly hot‐electron‐assisted S‐scheme photocatalysts for the broad‐spectrumutilization of solar light.展开更多
To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is reporte...To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is reported.The doping effect and the application of graphene as cocatalyst for CdS is studied for photocatalytic H_(2) generation.The most active sample consists of CdS and graphene(CdS-0.15G)exhibits promising photocatalytic activity,producing 3.12 mmol g^-(1) h^-(1) of H_(2) under simulated solar light which is^4.6 times superior than pure CdS nanoparticles giving an apparent quantum efficiency(AQY)of 11.7%.The enhanced photocatalytic activity for H_(2) generation is associated to the narrowing of the bandgap,enhanced light absorption,fast interfacial charge transfer,and higher carrier density(N_(D))in C-doped CdS@G samples.This is achieved by C doping in CdS nanoparticles and the formation of a graphene shell over the C-doped CdS nanoparticles.After stability test,the spent catalysts sample was also characterized to investigate the nanostructure.展开更多
We theoretically investigate the high-order-harmonic generation from the H2^＋ molecular ion exposed to the combi- nation of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum...We theoretically investigate the high-order-harmonic generation from the H2^＋ molecular ion exposed to the combi- nation of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum is obviously extended and the short quantum path is selected to contribute to the spectrum, because the corresponding long path is seriously suppressed. Then the combined Coulomb and laser field potentials and the time-dependent electron wave packet distributions are applied to illustrate the physical mechanism of high-order harmonic gen- eration. Finally, by adjusting the intensity of the static field and superposing a properly selected range of the HHG spectrum, a 90-as isolated attosecond pulse is straightforwardly obtained.展开更多
Hydrogen peroxide(H_(2)O_(2)) is a high-demand organic chemical reagent and has been widely used in various modern industrial applications. Currently,the prominent method for the preparation of H_(2)O_(2) is the anthr...Hydrogen peroxide(H_(2)O_(2)) is a high-demand organic chemical reagent and has been widely used in various modern industrial applications. Currently,the prominent method for the preparation of H_(2)O_(2) is the anthraquinone oxidation.Unfortunately, it is not conducive to economic and sustainable development since it is a complex process and involves unfriendly environment and potential hazards. In this context, numerous approaches have been developed to synthesize H_(2)O_(2). Among them, photo/electro-catalytic ones are considered as two of the most promising manners for on-site synthesis of H_(2)O_(2). These alternatives are sustainable in that only water or O_(2) is required. Namely, water oxidation(WOR) or oxygen reduction(ORR)reactions can be further coupled with clean and sustainable energy. For photo/electro-catalytic reactions for H_(2)O_(2) generation, the design of the catalysts is extremely important and has been extensively conducted with an aim to obtain ultimate catalytic performance. This article overviews the basic principles of WOR and ORR,followed by the summary of recent progresses and achievements on the design and performance of various photo/electro-catalysts for H_(2)O_(2) generation. The related mechanisms for these approaches are highlighted from theoretical and experimental aspects. Scientific challenges and opportunities of engineering photo/electro-catalysts for H_(2)O_(2) generation are also outlined and discussed.展开更多
Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous car...Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous carbon materials composed of abundant graphene/hexagonal boron nitride(G/h-BN)heterostructures.Metal Ni powder and nanoscale h-BN sheets are used as a catalytic substrate/hard template and“nucleation seed”for the formation of the heterostructure,respectively.As-prepared G/h-BN heterostructures exhibit enhanced electrocatalytic activity toward H_(2)O_(2) generation with 86%-95%selectivity at the range of 0.45-0.75 V versus reversible hydrogen electrode(RHE)and a positive onset potential of 0.79 versus RHE(defined at a ring current density of 0.3 mA cm^(-2))in the alkaline solution.In a flow cell,G/h-BN heterostructured electrocatalyst has a H_(2)O_(2) production rate of up to 762 mmol g_(catalyst)^(-1) h^(-1) and Faradaic efficiency of over 75%during 12 h testing,superior to the reported carbon-based electrocatalysts.The density functional theory simulation suggests that the B atoms at the interface of the G/h-BN heterostructure are the key active sites.This research provides a new route to activate carbon catalysts toward highly active and selective O_(2)-to-H_(2)O_(2) conversion.展开更多
SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature ...SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:21805166111 Project of China,Grant/Award Number:D20015+1 种基金Ministryof Education,Hubei province,China,Grant/Award Number:T2020004Foundation of Science and Technology Bureau of Yichang City,Grant/Award Number:A21‐3‐012。
文摘In spite of the numerous advances in the development of H_(2)and O_(2)evolutions upon water splitting,the separation of H_(2)from O_(2)still remains a severe challenge.Herein,the novel dual-functional nanocatalysts Pd/carbon nanosphere(CNS),obtained via immobilization of ultrafine Pd nanoparticles onto CNS,are developed and employed for both selective H_(2)generation from HCOOH dehydrogenation and O_(2)evolution from H_(2)O_(2)decomposition.In these reactions,the highest activities for Pd/CNS-800(i.e.,calcinated at 800℃)are 2478 h−1 and 993 min^(−1)for H_(2)and O_(2)evolution,respectively.The highly efficient and selective“on-off”switch for selective H_(2)generation from HCOOH is successfully realized by pH adjustment.This novel and highly efficient nanocatalyst Pd/CNS-800 not only provides new approaches for the promising application of HCOOH and H_(2)O_(2)as economic and safe H_(2)and O_(2)carriers,respectively,for fuel cells,but also promotes the development of“on-off”switch for on-demand H_(2)evolution.
基金supported by the Basic and Applied Basic Research Foundation of Guangdong Province(No.2022A1515011832 and 2021A1515110676)supported by GDAS’Project of Science and Technology Development(2022GDASZH-2022010104,2022GDASZH-2022030604-04).
文摘The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B_(2)O_(3)(or B(OH)_(3)).By adding small amounts of B_(2)O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B_(2)O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl_(2) in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl_(2) solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B_(2)O_(3) and recycling the 0.5 M MgCl_(2) solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.
文摘The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(MF)is very vital due to its existence in various sectors of industry and engineering.The present research focuses on mathematical modeling to simulate the cooling of a hot component through power-law(PL)nanofluid convection flow.The temperature reduction of the hot component inside a two-dimensional(2D)inclined chamber with two different cold wall shapes is evaluated.The formulation of the problem is derived with the lattice Boltzmann method(LBM)by code writing via the FORTRAN language.The variables such as the radiation parameter(0–1),the Hartmann number(0–75),the heat absorption/generation coefficient(−5–5),the fluid behavioral index(0.8–1.2),the Rayleigh number(103–105),the imposed MF angle(0°–90°),the chamber inclination angle(−90°–90°),and the cavity cold wall shape(smooth and curved)are investigated.The findings indicate that the presence of radiation increases the mean Nusselt number value for the shear-thickening,Newtonian,and shear thinning fluids by about 6.2%,4%,and 2%,respectively.In most cases,the presence of nanoparticles improves the heat transfer(HT)rate,especially in the cases where thermal conduction dominates convection.There is the lowest cooling performance index and MF effect for the cavity placed at an angle of 90°.The application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research.
基金National Natural Science Foundation of China(No.82160597)Guangxi Natural Science Foundation Project(No.2020GXNSFAA159148)。
文摘Objective: To explore the protective effect of camellia oil against H2O2-induced oxidative stress injury in rat H9C2 cardiomyocytes. Methods: CCK8 method was used to detect the cell survival rate of H9C2 cardiomyocytes treated with different concentrations of H2O2. Normal cultured cells were used as the blank control group, and the cells were treated with 200 μmol/L H2O2 for 24 h. An oxidative stress injury model was constructed as the model group. The cells were pretreated with 1%, 0.1% and 0.01% camellia oil for 24 h, and then H2O2 was added for 24 h as the experimental group. The β-galactosidase senescence staining assay, mitochondrial membrane potential assay, EdU cell proliferation staining assay and scratch assay were used to observe the changes of cell senescence, mitochondrial membrane potential, proliferation, apoptosis and migration in each group. The superoxide dismutase (SOD) activity, lactate dehydrogenase (LDH) activity, and malondialdehyde (MDA) content of the cells in each group were detected by using the kit. Results: The cell viability of H9C2 cardiomyocytes treated with different concentrations of H2O2 was inhibited and positively correlated with the concentration of H2O2 (P<0.01). Compared with the blank control group, the positive rate of cell senescence, MDA content and LDH activity increased in the H2O2 model group (P<0.01);mitochondrial membrane potential, cellular value-added rate, migration rate and SOD activity decreased (P<0.01). Compared with the H2O2 model group, the positive rate of cellular senescence (P<0.01 or P<0.05), MDA content and LDH activity decreased (P< 0.01 or P<0.05);mitochondrial membrane potential increased, cell proliferation rate and migration rate increased (P<0.01 or P<0.05) in the experimental group. Conclusion: Camellia oil can significantly inhibit oxidative stress injury in H9C2 cells and exert cardiomyocyte protective effects.
文摘Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.
基金supported by the National Natural Science Foundation of China(51602207)the Doctoral Scientific Research Foundation of Liaoning Province(20170520011)+3 种基金the Program for Liaoning Excellent Talents in Universities(LR2017074)the Open Project Program of the State Key Laboratory of Photocatalysis on Energy and Environment(SKLPEE-201810)Fuzhou University,the Scientific Research Project of the Educational Department of Liaoning Province(LQN201712)Shenyang Excellent Talents in Universities(RC180211)~~
文摘Photocatalytic water splitting is a promising method for hydrogen production.Numerous efficient photocatalysts have been synthesized and utilized.However,photocatalysts without a noble metal as the co-catalyst have been rarely reported.Herein,a CoP co-catalyst-modified graphitic-C3N4(g-C3N4/CoP)is investigated for photocatalytic water splitting to produce H2.The g-C3N4/CoP composite is synthesized in two steps.The first step is related to thermal decomposition,and the second step involves an electroless plating technique.The photocatalytic activity for hydrogen evolution reactions of g-C3N4 is distinctly increased by loading the appropriate amount of CoP quantum dots(QDs).Among the as-synthesized samples,the optimized one(g-C3N4/CoP-4%)shows exceptional photocatalytic activity as compared with pristine g-C3N4,generating H2 at a rate of 936μmol g^-1 h^-1,even higher than that of g-C3N4 with 4 wt%Pt(665μmol g^-1 h^-1).The UV-visible and optical absorption behavior confirms that g-C3N4 has an absorption edge at 451 nm,but after being composited with CoP,g-C3N4/CoP-4%has an absorption edge at 497 nm.Furthermore,photoluminescence and photocurrent measurements confirm that loading CoP QDs to pristine g-C3N4 not only enhances the charge separation,but also improves the transfer of photogenerated e--h+pairs,thus improving the photocatalytic performance of the catalyst to generate H2.This work demonstrates a feasible strategy for the synthesis of highly efficient metal phosphide-loaded g-C3N4 for hydrogen generation.
文摘Extended light absorption and dynamic charge separation are vital factors that determine the effectivenessof photocatalysts.In this study,a nonmetallic plasmonic S‐scheme photocatalyst was fabricatedby loading 1D plasmonic W_(18)O_(49)nanowires onto 2D g‐C_(3)N_(4)nanosheets.W_(18)O_(49)nanowiresplay the dual role of a light absorption antenna—that extends light adsorption—and a hot electrondonor—that assists the water reduction reaction in a wider light spectrum range.Moreover,S‐scheme charge transfer resulting from the matching bandgaps of W_(18)O_(49)and g‐C_(3)N_(4)can lead tostrong redox capability and high migration speed of the photoinduced charges.Consequently,in thisstudy,W_(18)O_(49)/g‐C_(3)N_(4)hybrids exhibited higher photocatalytic H2 generation than that of pristineg‐C_(3)N_(4)under light irradiation of 420–550 nm.Furthermore,the H2 production rate of thebest‐performing W_(18)O_(49)/g‐C_(3)N_(4)hybrid was 41.5μmol·g^(−1)·h^(−1)upon exposure to monochromaticlight at 550 nm,whereas pure g‐C_(3)N_(4)showed negligible activity.This study promotes novel andenvironmentally friendly hot‐electron‐assisted S‐scheme photocatalysts for the broad‐spectrumutilization of solar light.
基金support from the Research Council of Norway provided by the Norwegian Center for Transmission Electron Microscopy,NORTEM(197405/F50)NTNU NanoLab(grant number 245963)which have provided the characterization toolsthe strategic funding support provided by Department of Chemical Engineering,NTNU,Trondheim,Norway.
文摘To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is reported.The doping effect and the application of graphene as cocatalyst for CdS is studied for photocatalytic H_(2) generation.The most active sample consists of CdS and graphene(CdS-0.15G)exhibits promising photocatalytic activity,producing 3.12 mmol g^-(1) h^-(1) of H_(2) under simulated solar light which is^4.6 times superior than pure CdS nanoparticles giving an apparent quantum efficiency(AQY)of 11.7%.The enhanced photocatalytic activity for H_(2) generation is associated to the narrowing of the bandgap,enhanced light absorption,fast interfacial charge transfer,and higher carrier density(N_(D))in C-doped CdS@G samples.This is achieved by C doping in CdS nanoparticles and the formation of a graphene shell over the C-doped CdS nanoparticles.After stability test,the spent catalysts sample was also characterized to investigate the nanostructure.
基金Supported by the National Natural Science Foundation of China under Grant No 11404204the Key Project of the Ministry of Education of China under Grant No 211025+1 种基金the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20111404120004the Natural Science Foundation for Young Scientists of Shanxi Province of China under Grant No2009021005
文摘We theoretically investigate the high-order-harmonic generation from the H2^＋ molecular ion exposed to the combi- nation of an intense trapezoidal laser and a static field. The results show that the harmonic spectrum is obviously extended and the short quantum path is selected to contribute to the spectrum, because the corresponding long path is seriously suppressed. Then the combined Coulomb and laser field potentials and the time-dependent electron wave packet distributions are applied to illustrate the physical mechanism of high-order harmonic gen- eration. Finally, by adjusting the intensity of the static field and superposing a properly selected range of the HHG spectrum, a 90-as isolated attosecond pulse is straightforwardly obtained.
基金supported by Shanxi Province Science Foundation (20210302124446202102070301018)+1 种基金the National Natural Science Joint Foundation (U1710112)Basic Research Project from the Institute of Coal Chemistry, CAS (SCJC-HN-2022-17)。
文摘Hydrogen peroxide(H_(2)O_(2)) is a high-demand organic chemical reagent and has been widely used in various modern industrial applications. Currently,the prominent method for the preparation of H_(2)O_(2) is the anthraquinone oxidation.Unfortunately, it is not conducive to economic and sustainable development since it is a complex process and involves unfriendly environment and potential hazards. In this context, numerous approaches have been developed to synthesize H_(2)O_(2). Among them, photo/electro-catalytic ones are considered as two of the most promising manners for on-site synthesis of H_(2)O_(2). These alternatives are sustainable in that only water or O_(2) is required. Namely, water oxidation(WOR) or oxygen reduction(ORR)reactions can be further coupled with clean and sustainable energy. For photo/electro-catalytic reactions for H_(2)O_(2) generation, the design of the catalysts is extremely important and has been extensively conducted with an aim to obtain ultimate catalytic performance. This article overviews the basic principles of WOR and ORR,followed by the summary of recent progresses and achievements on the design and performance of various photo/electro-catalysts for H_(2)O_(2) generation. The related mechanisms for these approaches are highlighted from theoretical and experimental aspects. Scientific challenges and opportunities of engineering photo/electro-catalysts for H_(2)O_(2) generation are also outlined and discussed.
基金supported by the“National Natural Science Foundation of China (Nos.51902162,21901154)”the FoundationResearch Project of Jiangsu Province (BK20221338)+1 种基金Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources,International Innovation Center for Forest Chemicals and Materials,Nanjing Forestry University,merit-based funding for Nanjing innovation and technology projects,Shanghai Pujiang Program (21PJD022)the Foundation of Jiangsu Key Lab of Biomass Energy and Material (JSBEM-S-202101).
文摘Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous carbon materials composed of abundant graphene/hexagonal boron nitride(G/h-BN)heterostructures.Metal Ni powder and nanoscale h-BN sheets are used as a catalytic substrate/hard template and“nucleation seed”for the formation of the heterostructure,respectively.As-prepared G/h-BN heterostructures exhibit enhanced electrocatalytic activity toward H_(2)O_(2) generation with 86%-95%selectivity at the range of 0.45-0.75 V versus reversible hydrogen electrode(RHE)and a positive onset potential of 0.79 versus RHE(defined at a ring current density of 0.3 mA cm^(-2))in the alkaline solution.In a flow cell,G/h-BN heterostructured electrocatalyst has a H_(2)O_(2) production rate of up to 762 mmol g_(catalyst)^(-1) h^(-1) and Faradaic efficiency of over 75%during 12 h testing,superior to the reported carbon-based electrocatalysts.The density functional theory simulation suggests that the B atoms at the interface of the G/h-BN heterostructure are the key active sites.This research provides a new route to activate carbon catalysts toward highly active and selective O_(2)-to-H_(2)O_(2) conversion.
文摘SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.
