Oxygen‑Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.

An efficient and reusable bimetallic Ni_3Fe NPs@C catalyst for selective hydrogenation of biomass-derived levulinic acid toγ-valerolactone

Bimetallic nanostructures have attracted great interest as efficient catalyst to enhance activity,selectivity and stability in catalytical conversion.Herein,we report a facile one‐pot carbothermal route to in‐situ controllable synthesize heterogeneous bimetallic Ni3Fe NPs@C nanocatalyst.The X‐ray diffraction,transmission electron microscopy,X‐ray photoelectron spectroscopy and N2 adsorption‐description results reveal that the Ni3Fe alloy nanoparticles are evenly embedded in carbon matrix.The as‐prepared Ni3Fe NPs@C catalyst shows excellent selective hydrogenation catalytic performance toward the conversion of levulinic acid(LA)toγ‐valerolactone(GVL)via both direct hydrogenation(DH)and transfer hydrogenation(TH).In DH of LA,the bimetallic catalyst achieved a 93.8%LA conversion efficiency with a 95.5%GVL selectivity and 38.2 mmol g–1 h–1 GVL productivity(under 130°C,2MPa H2 within 2 h),which are 6 and 40 times in comparison with monometallic Ni NPs@C and Fe NPs@C catalysts,respectively.In addition,the identical catalyst displayed a full conversion of LA with almost 100%GVL selectivity and 167.1 mmol g–1 h–1 GVL productivity at 180°C within 0.5 h in TH of LA.Under optimal reaction conditions,the DH and TH catalytic performance of 500‐Ni3Fe NPs@C(3:1)catalyst for converting LA to GVL is comparable to the state‐of‐the‐art noble‐based catalysts.The demonstrated capability of bimetallic catalyst design approach to introduce dual‐catalytic functionality for DH and TH reactions could be adoptable for other catalysis processes.

Encapsulated Ni-Co alloy nanoparticles as efficient catalyst for hydrodeoxygenation of biomass derivatives in water

Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficient nonprecious metal catalysts.Herein,we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst.The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100%conversion efficiency and selectivity under mild reaction conditions,surpassing the reported high performance nonprecious HDO catalysts.Impressively,our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100%conversion efficiency and over 90%selectivity.Importantly,our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O,and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs.The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.

High-yield Production Techniques of High-quality and Early Maturity Hybrid Rice Xiangzaoyou 2017

Xiangzaoyou 2017 is an excellent early maturing variety bred from the combination of Neixiang 3A and the self-fertile restorer QN 2017 by Qiannan Institute of Agricultural Sciences of Guizhou Province,and it has been approved by the Guizhou Crop Variety Approval Committee( Approval No.: Qianshendao 2006001).In order to promote its application in production,the research on the seed production techniques of Xiangzaoyou 2017 was carried out,and the key technical points of high-yield seed production of Xiangzaoyou 2017 were put forward.

Heterostructure Cu_(3)P-Ni_(2)P/CP catalyst assembled membrane electrode for high-efficiency electrocatalytic nitrate to ammonia

Electrochemical nitrate reduction reaction(NO_(3)RR)is a promising means for generating the energy carrier ammonia.Herein,we report the synthesis of heterostructure copper-nickel phosphide electrocatalysts via a simple vapor-phase hydrothermal method.The resultant catalysts were evaluated for electrocatalytic nitrate reduction to ammonia(NH_(3))in three-type electrochemical reactors.In detail,the regulation mechanism of the heterogeneous Cu_(3)P-Ni_(2)P/CP-x for NO_(3)RR performance was systematically studied through the H-type cell,rotating disk electrode setup,and membrane-electrode-assemblies(MEA)electrolyzer.As a result,the Cu_(3)P-Ni_(2)P/CP-0.5 displays the practicability in an MEA system with an anion exchange membrane,affording the largest ammonia yield rate(RNH_(3))of 1.9 mmol·h^(−1)·cm^(−2),exceeding most of the electrocatalytic nitrate reduction electrocatalysts reported to date.The theoretical calculations and in-situ spectroscopy characterizations uncover that the formed heterointerface in Cu_(3)P-Ni_(2)P/CP is beneficial for promoting nitrate adsorption,activation,and conversion to ammonia through the successive hydrodeoxygenation pathway.

Retinal microvasculature is a potential biomarker for acute mountain sickness

Increased cerebral blood flow resulting from altered capillary level autoregulation at high altitudes leads to capillary overperfusion and then vasogenic cerebral edema,which is the leading hypothesis of acute mountain sickness(AMS).However,studies on cerebral blood flow in AMS have been mostly restricted to gross cerebrovascular endpoints as opposed to the microvasculature.This study aimed to investigate ocular microcirculation alterations,the only visualized capillaries in the central neural system(CNS),during early-stage AMS using a hypobaric chamber.This study found that after high altitude simulation,the optic nerve showed retinal nerve fiber layer thickening(P=0.004–0.018)in some locations,and the area of the optic nerve subarachnoid space(P=0.004)enlarged.Optical coherence tomography angiography(OCTA)showed increased retinal radial peripapillary capillary(RPC)flow density(P=0.003–0.046),particularly on the nasal side of the nerve.The AMSpositive group had the largest increases in RPC flow density in the nasal sector(AMS-positive,?3.21±2.37;AMS-negative,?0.01±2.16,P=0.004).Among multiple ocular changes,OCTA increase in RPC flow density was associated with simulated early-stage AMS symptoms(beta=0.222,95%CI,0.009–0.435,P=0.042).The area under the receiver operating characteristics curve(AUC)for the changes in RPC flow density to predict early-stage AMS outcomes was 0.882(95%CI,0.746–0.998).The results further confirmed that overperfusion of microvascular beds is the key pathophysiologic change in early-stage AMS.RPC OCTA endpoints may serve as a rapid,noninvasive potential biomarker for CNS microvascular changes and AMS development during risk assessment of individuals at high altitudes.

Fe/Fe2O3 nanoparticles anchored on Fe-N-doped carbon nanosheets as bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

Electrocatalysts with high catalytic activity and stability play a key role in promising renewable energy technologies, such as fuel cells and metal-air batteries. Here, we report the synthesis of Fe/Fe203 nanoparticles anchored on Fe-N-doped carbon nanosheets （Fe/Fe2Og@Fe-N-C） using shrimp shell-derived N-doped carbon nanodots as carbon and nitrogen sources in the presence of FeCI3 by a simple pyrolysis approach. Fe/Fe203@Fe-N-C obtained at a pyrolysis temperature of 1,000 ℃ （Fe/Fe2OB@Fe-N-C-1000） possessed a mesoporous structure and high surface area of 747.3 m2-g-1. As an electrocatalyst, Fe/Fe203@Fe-N-C-1000 exhibited bifunctional electrocatalytic activities toward the oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） in alkaline media, com- parable to that of commercial Pt/C for ORR and RuO2 for OER, respectively. The Zn-air battery test demonstrated that Fe/Fe2OB@Fe-N-C-1000 had a superior rechargeable performance and cycling stability as an air cathode material with an open drcuit voltage of 1.47 V （vs. Ag/AgCl） and a power density of 193 mW.cm-2 at a current density of 220 mA-cm-2. These performances were better than other commercial catalysts with an open circuit voltage of 1.36 V and a power density of 173 mW-cm^-2 at a current density of 220 mA.cm-2 （a mixture of commercial Pt/C and RuO2 with a mass ratio of 1：1 was used for the rechargeable Zn-air battery measurements）. This work will be helpful to design and develop low-cost and abundant bifunctional oxygen electrocatalysts for future metal-air batteries.

Meaningful comparison of photocatalytic properties of {001} and {101} faceted anatase TiO2 nanocrystals

The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distinction in the photocatalytic oxidation activities between the {001}and {101} facets of anatase TiO_2 nanocrystals is still unclear and under debate. In this work, a simple photoelectrochemical method was employed to meaningfully quantify the intrinsic photocatalytic activities of {001} and{101} faceted TiO_2 nanocrystal photoanodes. The effective surface areas of photoanodes with different facets were measured based on the monolayer adsorption of phthalic acid on TiO_2 photoanode surface by an ex situ photoelectrochemical method, which were used to normalize the photocurrents obtained from different faceted photoanodes for meaningful comparison of their photocatalytic activities. The results demonstrated that the {001} facets of anatase TiO_2 nanocrystals exhibited much better photocatalytic activity than that of {101} facets of anatase TiO_2 nanocrystals toward photocatalytic oxidation of water and organic compounds with different functional groups(e.g.,–OH, –CHO, –COOH). Furthermore, the instantaneous kinetic constants of photocatalytic oxidation of pre-adsorbates on {001} faceted anatase TiO_2 photoanode are obviously greater than those obtained at {101} faceted anatase TiO_2 photoanode, further verifying the higher photocatalytic activity of {001} facets of anatase TiO_2.This work provided a facile photoelectrochemical method to quantitatively determine the photocatalytic oxidation activity of specific exposed crystal facets of a photocatalyst, which would be helpful to uncover and meaningfully compare the intrinsic photocatalytic activities of different exposed crystal facets of a photocatalyst.

Synergistic catalysis of cluster and atomic copper induced by copper-silica interface in transfer-hydrogenation

To data,using strong metal-support interaction(SMSI)effect to improve the catalytic performance of metal catalysts is an important strategy for heterogeneous catalysis,and this effect is basically achieved by using reducible metal oxides.However,the formation of SMSI between metal and inert-support has been so little coverage and remains challenge.In this work,the SMSI effect can be effectively extended to the inert support-metal catalysis system to fabricate a Cu^(0)/Cu-doped SiO_(2) catalyst with high dispersion and loading(38.5 wt.%)through the interfacial effect of inert silica.In the catalyst,subnanometric composite of Cu cluster and atomic copper(in the configuration of Cu-O-Si)can be consciously formed on the silica interface,and verified by extended X-ray absorption fine structure(EXAFS),in situ X-ray photoelectron spectroscopy(XPS),and high-angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)characterization.The promoting activity in transfer-hydrogenation by the SMSI effect of Cu-silica interface and the synergistic active roles of cluster and atomic Cu have also been revealed from surface interface structure,catalytic activity,and density functional theory(DFT)theoretical calculation at an atomic level.The subnanometric composite of cluster and atomic copper species can be derived from a facile synthesis strategy of metal-inert support SMSI effect and the realistic active site of Cu-based catalyst can also been identified accurately,thus it will help to expand the application of subnanometric materials in industrial catalysis.

Sulfonate group modified Ni catalyst for highly efficient liquid-phase selective hydrogenation of bio-derived furfural

The liquid-phase furfural （FAL） hydrogenation to furfuryl alcohol （FOL） and tetrahydrofurfuryl alcohol （THFOL） was investigated using sulfonate group （-SO3H） grafted activated carbon （AC） supported Ni catalyst, which was prepared and activated simultaneously by liquid phase reduction method. This functionalized nickel catalyst demonstrated an enhanced catalytic performance for selective hydrogenation of FAL, in which almost 100% FOL （〈80℃） and THFOL （〉100℃） selectivity with complete conversion was obtained, respectively. More importantly, the conversion of transfer hydrogenation of FAL to FOL also can reach almost 100% under optimal conditions （140℃, 4.0h）. The effect of -SO3H was evaluated and systematically analyzed by the combination of reaction performance and physico-chemical characterizations. Cycling test proved the prepared catalyst could be recycled and reused for several times without noticeably reducing catalytic activity of hvdrogenation.

Converting Co^(2+)-impregnated g-C_(3)N_(4) into N-doped CNTs-confined Co nanoparticles for efficient hydrogenation rearrangement reactions of furanic aldehydes

The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes.Here,we demonstrated a new synthetic approach to directly fabricate N-doped carbon nanotube(N-CNTs)networks with confined Co nanoparticles from Co^(2+)-impregnated bulk g-C_(3)N_(4) as high performance hydrogenation rearrangement(HR)catalyst to efficiently convert a wide spectrum of biomass-derived furanic aldehydes to the corresponding cyclopentanones in water under a record-low H2 pressure of 0.5 MPa and mild temperature.We unveiled a Co-catalysed bulk g-C_(3)N_(4) decomposition/carbonisation CNTs formation mechanism.A new HR pathway was also unveiled.

Highly ordered Nb_(2)O_(5)nanochannel film with rich oxygen vacancies for electrocatalytic N2 reduction:Inactivation and regeneration of electrode

We report the fabrication of highly ordered Nb_(2)O_(5)nanochannel film(Nb_(2)O_(5)-NCF)onto niobium foil by an anodization method.After thermal treatment,the obtained Nb_(2)O_(5)-NCF with rich oxygen vacancies exhibits electrochemical N_(2)reduction reaction(NRR)activity with an NH3 yield rate of 2.52×10^(-10)mol cm^(-2)s^(-1)and a faradaic efficiency of 9.81%at-0.4 V(vs.RHE)in 0.1 mol/L Na2SO4 electrolyte(pH 3.2).During electrocatalytic NRR,the Nb_(2)O_(5)-NCF takes place electrochromism(EC),along with a crystalline phase transformation from pseudo hexagonal phase to hexagonal phase owing to H+insertion.This results in the reduced NRR activity due to the decrease of oxygen vacancies of hexagonal phase Nb_(2)O_(5),which can be readily regenerated by low-temperature thermal treatment or applying an anodic potential,showing superior recycling reproducibility.

Robust enhanced hydrogen production at acidic conditions over molybdenum oxides-stabilized ultrafine palladium electrocatalysts

Electrochemical water splitting is quite seductive for eco-friendly hydrogen fuel energy production,however,the attainment of highly efficient,durable,and cheap catalysts for the hydrogen evolution reaction(HER)remains challenging.In this study,molybdenum oxides stabilized palladium nanoparticle catalysts(MoO_(x)-Pd)are in situ prepared on commercial carbon cloth(CC)by the facile two-step method of dip-coating and electrochemical reduction.As a self-supported Pd-based catalyst electrode,the MoO_(x)-Pd/CC presents a competitive Tafel slope of 45.75 mV·dec^(-1),an ultralow overpotential of 25 mV,and extremely long cycling durability(one week)in 0.5M H_(2)S0_(4)electrolyte,superior to unmodified Pd catalysts and comparable to commercial Pt mesh electrode.On the one hand,the introduction of MoO_(x)can inhibit the growth of Pd particles to obtain ultrafine Pd nanoparticles,thus exposing more available active sites.On the other hand,density functional theory(DFT)calculation revealed that MoO_(x)on the surface of Pd metal can regulate the electronic structure of Pd metal and enhance its intrinsic catalytic activity of HER.This work suggests that transitional metal nanoparticles stabilized by molybdenum oxides are hopeful approaches for obtaining fruitful hydrogen-producing electrocatalysts.

Integration of Fe_(2)O_(3)-based photoanode and atomically dispersed cobalt cathode for efficient photoelectrochemical NH_(3) synthesis

Realizing nitrogen reduction reaction(NRR) to synthesis NH_(3) under mild conditions has gained extensive attention as a promising alternative way to the energy-and emission-intensive Haber-Bosch process.Among varieties of potential strategies,photoelectrochemical(PEC) NRR exhibits many advantages including utilization of solar energy,water(H_(2)O) as the hydrogen source and ambient operation conditions.Herein,we have designed a solar-driven PEC-NRR system integrating high-efficiency Fe_(2)O_(3)-based photoanode and atomically dispersed cobalt(Co) cathode for ambient NH3 synthesis.Using such solar-driven PEC-NRR system,high-efficiency Fe_(2)O_(3)-based photoanode is responsible for H_(2)O/OH oxidatio n,and meanwhile the generated photoelectrons transfer to the single-atom Co cathode for the N_(2) reduction to NH_(3).As a result,this system can afford an NH_(3) yield rate of 1021.5 μg mg_(co)^(-1) h^(-1) and a faradic efficiency of 11.9% at an applied potential bias of 1.2 V(versus reversible hydrogen electrode) on photoanode in 0.2 mol/L NaOH electrolyte under simulated sunlight irradiation.

Growth and in situ transformation of TiO2 and HTiOF3 crystals on chitosan-polyvinyl alcohol co-polymer substrates under vapor phase hydrothermal conditions

A chitosan-polyvinyl alcohol （CS/PVA） co-polymer substrate possessing a large number of amino and hydroxyl groups is used as a substrate to induce the direct growth and in situ sequential transformation of fitanate crystals under HF vapor phase hydrothermal conditions. The process involves four distinct formation/ transformation stages. HTiOF3 crystals with well-defined hexagonal shapes are formed during stage I, and are subsequently transformed into {001} faceted anatase TiO2 crystal nanosheets during stage II. Interestingly, the formed anatase TiO2 crystals are further transformed into cross-shaped and hollow square- shaped HTiOF3 crystals during stages III and IV, respectively. Although TiO2 crystal phases and facet transformations under hydrothermal conditions have been previously reported, in situ crystal transformations between different titanate compounds have not been widely reported. Such crystal formation/ transformations are likely due to the presence of large numbers of amino groups in the CS/PVA substrate. When celluloses possessing only hydroxyl groups are used as a substrate, the direct formation of {001} faceted TiO2 nanocrystal sheets is observed （rather than any sequential crystal transformations）. This substrate organic functional group-induced crystal formation/transformation approach could be applicable to other material systems.

Interfacial engineering of metallic rhodium by thiol modification approach for ambient electrosynthesis of ammonia

Here we report a vapor-phase reaction approach to fabricate rhodium(I)-dodecanethiol complex coated on carbon fiber cloth(Rh(I)-SC_(12)H_(25)/CFC),followed by low-temperature pyrolysis to achieve dodecanethiol modified Rh(Rh@SC_(12)H_(2)5/CFC)for electrocatalytic nitrogen reduction reaction(NRR).The results demonstrate that after pyrolysis for 0.5 h at 150℃,the obtained Rh@SC_(12)H_(2)5/CFC-0.5 exhibits excellent NRR activity with an NH3 yield rate of 121.2±6.6μg∙h^(−1)∙cm^(−2)(or 137.7±7.5μg∙h^(−1)∙mgRh^(−1))and a faradaic efficiency(FE)of 51.6%±3.8%at−0.2 V(vs.RHE)in 0.1 M Na_(2)SO_(4).The theoretical calculations unveil that the adsorption of dodecanethiol on the hollow sites of Rh(111)plane is thermodynamically favorable,effectively regulating the electronic structure and surface wettability of metallic Rh.Importantly,the dodecanethiol modification on Rh(111)obviously decreases the surface H*coverage,thus inhibiting the competitive hydrogen evolution reaction and concurrently reducing the electrocatalytic NRR energy barrier.

hcp-phased Ni nanoparticles with generic catalytic hydrogenation activities toward different functional groups

Catalytic hydrogenation is a vital industrial means to produce value-added fuels and fine chemicals,however, requiring highly efficient catalysts, especially the nonprecious ones. To date, the majority of high-performance industrial hydrogenation catalysts are made of precious metals-based materials, and any given catalyst could only be used to catalyze one or few specific reactions. Herein, we exemplify a crystal phase engineering approach to empower Ni nanoparticles(NPs) with superb intrinsic catalytic activities toward a wide spectrum of hydrogenation reactions. A facile pyrolysis approach is used to directly convert a Ni-imidazole MOF precursor into hexagonal close-packed(hcp)-phased Ni NPs on carbon support. The as-synthesized hcp-phased Ni NPs exhibit unprecedented hydrogenation catalytic activities in pure water towards nitro-, aldehyde-, ketone-, alkene-and N heterocyclic-compounds, outperforming the face-centered cubic(fcc)-Ni counterpart and the reported transition metalsbased catalysts. The density functional theory calculations unveil that the presence of hcp-Ni boosts the intrinsic catalytic hydrogenation activity by coherently enhancing the substrate adsorption strength and lowering the reaction barrier energy of the rate-determining step. We anticipate that the crystal phase engineering design approach unveiled in this work would be adoptable to other types of reactions.

Pseudocapacitive desalination via valence engineering with spindle-like manganese oxide/carbon composites

Manganese tetravalent oxide(MnO_(2)),a superstar Faradic electrode material,has been investigated extensively for capacitive desalination,enabling higher salt adsorption capacity compared to the great majority of carbonous electrodes.However,few works paid attention on the relationship between the valences of manganese oxide and their desalination performance.For the first time,we prepared the spindle-like manganese oxides/carbon composites with divalent(MnO@C),trivalent(Mn_(2)O_(3)@C)and divalent/trivalent(Mn_(3)O_(4)@C)manganese by pyrolysis of manganese carbonate precursor under different condition,respectively.The electrochemical behavior in three-electrode system and electrosorption performance obtained in hybrid membrane capacitive deionization(HMCDI)cells assembled with capacitive carbon electrodes were systematically evaluated,respectively.High salt adsorption capacity(as large as 31.3,22.2,and 18.9 mg·g^(−1))and corresponding average salt adsorption rates(0.83,0.53,and 1.71 mg·g^(−1)min−1)were achieved in 500 mg·L^(−1) NaCl solution for MnO@C,Mn_(2)O_(3)@C,and Mn_(3)O_(4)@C,respectively.During fifteen electrosorption-desorption cycles,ex-situ water contact angle and morphology comparison analysis demonstrated the superior cycling durability of the manganese oxide electrodes and subtle difference between their surface redox.Furthermore,density functional theory(DFT)was also conducted to elaborate the disparity among the valence states of manganese(+2,+3 and +2/+3)for in-depth understanding.This work introduced manganese oxide with various valences to blaze new trails for developing novel Faradic electrode materials with high-efficiency desalination performance by valence engineering.