Nanocarbons are of progressively increasing importance in energy electrocatalysis, including oxygen reduction, oxygen evolution, hydrogen evolution, COreduction, etc. Precious-metal-free or metal-free nanocarbon-based...Nanocarbons are of progressively increasing importance in energy electrocatalysis, including oxygen reduction, oxygen evolution, hydrogen evolution, COreduction, etc. Precious-metal-free or metal-free nanocarbon-based electrocatalysts have been revealed to potentially have effective activity and remarkable durability, which is promising to replace precious metals in some important energy technologies,such as fuel cells, metal–air batteries, and water splitting. In this review, rather than overviewing recent progress completely, we aim to give an in-depth digestion of present achievements, focusing on the different roles of nanocarbons and material design principles. The multifunctionalities of nanocarbon substrates(accelerating the electron and mass transport, regulating the incorporation of active components,manipulating electron structures, generating confinement effects, assembly into 3 D free-standing electrodes) and the intrinsic activity of nanocarbon catalysts(multi-heteroatom doping, hierarchical structure,topological defects) are discussed systematically, with perspectives on the further research in this rising research field. This review is inspiring for more insights and methodical research in mechanism understanding, material design, and device optimization, leading to a targeted and high-efficiency development of energy electrocatalysis.展开更多
The explore and development of electrocatalysts have gained significant attention due to their indispensable status in energy storage and conversion systems, such as fuel cells, metal–air batteries and solar water sp...The explore and development of electrocatalysts have gained significant attention due to their indispensable status in energy storage and conversion systems, such as fuel cells, metal–air batteries and solar water splitting cells. Layered double hydroxides（LDHs） and their derivatives（e.g., transition metal alloys, oxides, sulfides, nitrides and phosphides） have been adopted as catalysts for various electrochemical reactions, such as oxygen reduction, oxygen evolution, hydrogen evolution, and COreduction, which show excellent activity and remarkable durability in electrocatalytic process. In this review, the synthesis strategies, structural characters and electrochemical performances for the LDHs and their derivatives are described. In addition, we also discussed the effect of electronic and geometry structures to their electrocatalytic activity. The further development of high-performance electrocatalysts based on LDHs and their derivatives is covered by both a short summary and future outlook from the viewpoint of the material design and practical application.展开更多
Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidatio...Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.展开更多
Most advanced hydrogen evolution reaction(HER)catalysts show high activity under alkaline conditions.However,the performance deteriorates at a natural and acidic pH,which is often problematic in practical applications...Most advanced hydrogen evolution reaction(HER)catalysts show high activity under alkaline conditions.However,the performance deteriorates at a natural and acidic pH,which is often problematic in practical applications.Herein,a rhenium(Re)sulfide–transition-metal dichalcogenide heterojunc-tion catalyst with Re-rich vacancies(NiS_(2)-ReS_(2)-V)has been constructed.The optimized catalyst shows extraordinary electrocatalytic HER performance over a wide range of pH,with ultralow overpotentials of 42,85,and 122 mV under alkaline,acidic,and neutral conditions,respectively.Moreover,the two-electrode system with NiS_(2)-ReS_(2)-V1 as the cathode provides a voltage of 1.73 V at 500 mA cm^(-2),superior to industrial systems.Besides,the open-circuit voltage of a single Zn–H_(2)O cell with NiS_(2)-ReS_(2)-V1 as the cathode can reach an impressive 90.9% of the theoretical value,with a maximum power density of up to 31.6 mW cm^(-2).Moreover,it shows remarkable stability,with sustained discharge for approximately 120 h at 10 mA cm^(-2),significantly outperforming commercial Pt/C catalysts under the same conditions in all aspects.A series of systematic characterizations and theoretical calculations demonstrate that Re vacancies on the heterojunction interface would generate a stronger built-in electric field,which profoundly affects surface charge distribution and subsequently enhances HER performance.展开更多
To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Ach...To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.展开更多
Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen ...Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen was chemically stored by use of a 1,4-benzoquinone/1,4-hydroquinone system, which was used as a recyclable fuel in a commercialised direct methanol fuel cell (DMFC). The electrical output of the cell was about half compared to methanol. The conversion process for water splitting and recombination in a fuel cell was monitored by UV-Vis spectroscopy and compared to a simulated spectrum. Products of side reactions, which lead to a decrease of the overall efficiency, were identified based on UV-Vis investigations. A proof of principle for the use of quinoide systems as a recyclable hydrogen storage system in a photocatalytic water splitting and fuel cell cyclic process was given.展开更多
CdS sensitized NiO electrode was used as the photoactive cathode in a photoelectrochemical cell for water splitting,avoiding the use of a sacrificial electron donor.Photocurrent increment under visible light irradiati...CdS sensitized NiO electrode was used as the photoactive cathode in a photoelectrochemical cell for water splitting,avoiding the use of a sacrificial electron donor.Photocurrent increment under visible light irradiation was observed after integration of[Co（dmgH）_2（4-Me-py）Cl]（1） to the photocathode,suggesting 1 could accept electrons from photoexcited CdS for water reduction and NiO could move the holes in the valence band of CdS to anode for water oxidation.展开更多
Although monoclinic WO3 is widely studied as a prototypical photoanode material for solar water splitting,limited success,hitherto,in fabricating WO3 photoanodes that simultaneously demonstrate high efficiency and rep...Although monoclinic WO3 is widely studied as a prototypical photoanode material for solar water splitting,limited success,hitherto,in fabricating WO3 photoanodes that simultaneously demonstrate high efficiency and reproducibility has been realized.The difficulty in controlling both the efficiency and reproducibility is derived from the ever-changing structures/compositions and chemical environments of the precursors,such as peroxytungstic acid and freshly prepared tungstic acid,which render the fabrication processes of the WO3 photoanodes particularly uncontrollable.Herein,a highly reproducible sol-gel process was developed to establish efficient and translucent WO3 photoanodes using a chemically stable ammonium metatungstate precursor.Under standard simulated sunlight of air mass 1.5 G,100 m W cm-2,the WO3 photoanode delivered photocurrent densities of ca.2.05 and2.25 m A cm^-2at 1.23 V versus the reversible hydrogen electrode(RHE),when tested in 1 mol L^-1H2SO4 and CH3SO3H,respectively.Hence,the WO3 photoanodes fabricated herein are one of the WO3 photoanodes with the highest performance ever reported.The reproducibility of the fabrication scheme was evaluated by testing 50 randomly selected WO3 samples in1 mol L^-1H2SO4,which yielded an average photocurrent density of 1.8 m A cm^-2at 1.23 VRHEwith a small standard deviation.Additionally,the effectiveness of the ammonium metatungstate precursor solution was maintained for at least 3weeks,when compared with the associated upper-limit values of peroxytungstic and tungstic acid-based precursors after 3 d.This study presents a key step to the future development of WO3 photoanodes for efficient solar water splitting.展开更多
A series of novel calix[4]arene metal-free dyes,featuring macrocyclic structure and unique conical confor mation,has been introduced into photoanode-based dye-sensitized electrochemical cell system as photosensitizers...A series of novel calix[4]arene metal-free dyes,featuring macrocyclic structure and unique conical confor mation,has been introduced into photoanode-based dye-sensitized electrochemical cell system as photosensitizers.The electrochemical properties of the corresponding sensitized photoanodes were systematically studied in the absence.presence of water oxidation catalyst(WOC).Furthermore,the visible-light-driven overall water-splitting reactions wero conducted by fully assembled devices,obtaining a performance trend of Calix-3>Calix-2 Calix-1.The correspondins device of Calix-3 exhibited the best photoactivity,giving an initial photocurrent density of ca.300 pA/cm^2,an IPEC peak value of ca.9.0%at 365 nm and a wide photo-respond band up to ca.620 nm.The best performance of Calix-3 an be attributed to its most effective light-harvesting ability,best ICT transition property,highest oxidation potentiaand thus best ability of activating WOC.This work offers an inspiration for the application of new-type effective metal-free sensitizers in photocatalytic water-splitting device.展开更多
Electrocatalytic water splitting driven by renewable energy input to produce clean hydrogen(H_(2))has been widely considered a prospective approach for a future hydrogen-based society.However,the development of indust...Electrocatalytic water splitting driven by renewable energy input to produce clean hydrogen(H_(2))has been widely considered a prospective approach for a future hydrogen-based society.However,the development of industrial alkaline water electrolyzers is hindered due to their unfavorable thermodynamics with high overpotential for delivering the whole process,caused by sluggish kinetics involving four-electron transfer.Further exploration of water electrolysis with low energy consumption and high efficiency is urgently required to meet the ever-growing energy storage and portfolio demands.This review emphasizes the strategies proposed thus far to pursue high-efficiency water electrolysis systems,including from the aspects of electro-catalysts(from monofunctional to bifunctional),electrode engineering(from powdery to self-supported),energy sources(from nonrenewable to renewable),electrolytes(from pure to hybrid),and cell configurations(from integrated to decoupled).Critical appraisals of the pivotal electrochemistry are highlighted to address the challenges in elevating the overall efficiency of water splitting.Finally,valuable insights for the future development directions and bottlenecks of advanced,sustainable,and high-efficiency water splitting systems are outlined.展开更多
A new class of second order accuracy semidiscrete difference schemes is presented for the two-dimensional nonlinear scalar hyperbolic conservation laws. It is based on flux splitting, piecewise linear cell-averaged re...A new class of second order accuracy semidiscrete difference schemes is presented for the two-dimensional nonlinear scalar hyperbolic conservation laws. It is based on flux splitting, piecewise linear cell-averaged reconstruction and upwind property in the spatial discretization. By using TVD Runge-Kutta time discretization method, the full discrete scheme is obtained and its MmB property is proved. The extension to the two-dimensionalnonlinear hyperbolic conservation law systems is straightforward by using component-wise manner. The main advantage is simple: no Riemann problem is solved, and so field-by-field decomposition is avoided and the complicated computation is reduced. Numerical results of two-dimensional Euler equations of compressible gas dynamics verify the accuracy and robustness of the method.展开更多
Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water‐splitting photoelectrodes.In our previous study,the electrochemical activation of Mo‐doped BiVO...Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water‐splitting photoelectrodes.In our previous study,the electrochemical activation of Mo‐doped BiVO_(4) electrodes was ascribed to the removal of MoO_(x) segregations,which are considered to be surface recombination centers for photoinduced electrons and holes.However,this proposed mechanism cannot explain why activated Mo‐doped BiVO_(4) electrodes gradually lose their activity when exposed to air.In this study,based on various characterizations,it is suggested that electrochemical treatment not only removes partial MoO_(x) segregations but also initiates the formation of H_(y)MoO_(x) surface defects,which provide charge transfer channels for photogenerated holes.The charge separation of the Mo‐doped BiVO_(4) electrode was significantly enhanced by these charge transfer channels.This study offers a new insight into the electrochemical activation of Mo‐doped BiVO_(4) photoanodes,and the new concept of surface charge transfer channels,a long overlooked factor,will be valuable for the development of other(photo)electrocatalytic systems.展开更多
This study deals with the optimization of best working conditions in molten melt for the production of hydrogen(H2) gas.Limited research has been carried out on how electrochemical process occurs through steam splitti...This study deals with the optimization of best working conditions in molten melt for the production of hydrogen(H2) gas.Limited research has been carried out on how electrochemical process occurs through steam splitting via molten hydroxide.54 combinations of cathode,anode,temperature and voltage have been investigated for the optimization of best working conditions with molten hydroxide for hydrogen gas production.All these electrochemical investigations were carried out at 225 to 300℃ temperature and 1.5 to 2.5 V applied voltage values.The current efficiency of 90.5,80.0 and 68.6% has been achieved using stainless steel anodic cell with nickel,stainless steel and platinum working cathode respectively.For nickel cathode,an increase in the current directly affected the hydrogen gas flow rate at cathode.It can be hypothesized from the noted results that increase in current is directly proportional to operating temperature and applied voltage.Higher values were noted when the applied voltages increased from 1.5 to 2.5 V at 300℃,the flow rate of hydrogen gas increased from 1.5 to 11.3 cm^(3) min^(-1),1.0 to 13 cm^(3) min^(-1) in case of electrolysis@stainless steel and@graphite anode respectively.It is observed that the current efficiency of stainless steel anodic cell was higher than the graphite anodic cell.Therefore,steam splitting with the help of molten salts has shown an encouraging alternate to current methodology for H2 fuel production.展开更多
The hydrogen evolution reaction(HER)is the cathodic process of water splitting,and its reverse,the hydrogen oxidation reaction(HOR),is the anodic process of an H-Ofuel cell;both play important roles in the development...The hydrogen evolution reaction(HER)is the cathodic process of water splitting,and its reverse,the hydrogen oxidation reaction(HOR),is the anodic process of an H-Ofuel cell;both play important roles in the development of hydrogen energy.The rational design and scalable fabrication of low-cost and efficient bifunctional catalysts for the HER/HOR are highly desirable.Herein,ultrasmall Mo-Ru nanoalloy(Mo_(0.5)Ru_(3)and Mo_(0.5)Ru_(3))particles uniformly distributed on mesoporous carbon(MPC)were successfully synthesized by a simple method that is easy to scale up for mass production.After the incorporation of Mo atoms,the as-prepared Mo_(0.5)Ru_(3)and Mo_(0.5)Ru_(3)nanoalloys maintain a hexagonal-close-packed crystal structure.In acidic media,Mo_(0.5)Ru_(3)exhibits excellent Pt-like HER and HOR activity,as well as good stability.Density functional theory(DFT)calculations reveal that the H adsorption free energy(ΔG)on the Mo_(0.5)Ru_(3)(001)surface(-0.09 eV)is much closer to zero than that of metallic Ru(-0.22 eV),which contributes to the enhanced catalytic activity.In alkaline media,Mo_(0.5)Ru_(3)also presents outstanding HER and HOR activity,even significantly outperforming Pt/C.The DFT results confirm that optimal binding energies with H*and OH*intermediate species,and low energy barriers in the water dissociation and formation steps,efficiently accelerate the alkaline HER/HOR kinetics of Mo_(0.5)Ru_(3).This study provides a new avenue for the scalable fabrication of high-efficiency bifunctional electrocatalysts for the HER and HOR in both acidic and alkaline media.展开更多
van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable t...van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable the band-offset construction and facilitate the charge separation. They also provide a platform for the study of various of interface effect in PEC. Here, we report a new kind of mixed-dimensional vdWs heterostructure photoelectrode and investigate the strain enhanced PEC performance at vdWs interfaces. Our heterostructures are composed of 2D n-type MoS_(2) nanosheets and three-dimensional (3D) p-type Cu_(2)O nanorod arrays (NRAs), where Cu_(2)O NRAs introduce periodically strain in the p-n junction interface. We find a promotion of the HER catalytic activities in heterostructure based PEC photoelectrodes using in-situ measurement techniques including the scanning electrochemical cell microscopy and various local spectrum probe measurements. This is attributed to the efficient charge separation at the strained heterointerface. Our results demonstrate an interesting venue for understanding the local interface effects with high spatial resolution, and shed light on design and developing high-efficiency photoelectrodes. 1L MoS_(2)/Cu_(2)O vdWs heterostructure photocathodes were prepared by nanoindentation technology. The effects of strain on promoting charge separation at the heterointerface were verified by the enhanced performances in PEC hydrogen evolution reaction of vdWs heterostructure through scanning electrochemical cell microscopy technique and various local spectrum probe measurements.展开更多
The development of high-efficiency electrocatalysts for oxygen evolution reactions （OERs） plays an important role in the water-splitting process. Herein, we report a facile way to obtain two-dimensional （2D） singl...The development of high-efficiency electrocatalysts for oxygen evolution reactions （OERs） plays an important role in the water-splitting process. Herein, we report a facile way to obtain two-dimensional （2D） single-unit-cell-thick layered double hydroxide （LDH） nanosheets （NSs, - 1.3 nm） within only 5 min. These nanosheets presented significantly enhanced OER performance compared to bulk LDH systems fabricated using the conventional co-precipitation method. The current strategy further allowed control over the chemical compositions and electrochemical activities of the LDH NSs. For example, CoFe-LDH NSs presented the lowest overpotential of 0.28 V at 10 mA/cm2, and the NiFe-LDHs NSs showed Tafel slopes of 33.4 mV/decade and nearly 100% faradaic efficiency, thus outperforming state-of-the-art IrO2 water electrolysis catalysts. Moreover, positron annihilation lifetime spectroscopy and high-resolution transmission electron microscopy observations confirmed that rich defects and distorted lattices occurred within the 2D LDH NSs, which could supply abundant electrochemically active OER sites. Periodic calculations based on density functional theory （DFT） further showed that the CoFe- and NiFe-LDHs presented very low energy gaps and obvious spin-polarization behavior, which facilitated high electron mobility during the OER process. Therefore, this work presents a combined experimental and theoretical study on 2D single-unit-cell-thick LDH NSs with high OER activities, which have potential application in water splitting for renewable energy.展开更多
基金supported by the National Key Research and Development Program (Nos. 2016YFA0202500 and 2016YFA0200102)the Natural Scientific Foundation of China (No. 21561130151)Royal Society for the award of a Newton Advanced Fellowship (Ref: NA140249)
文摘Nanocarbons are of progressively increasing importance in energy electrocatalysis, including oxygen reduction, oxygen evolution, hydrogen evolution, COreduction, etc. Precious-metal-free or metal-free nanocarbon-based electrocatalysts have been revealed to potentially have effective activity and remarkable durability, which is promising to replace precious metals in some important energy technologies,such as fuel cells, metal–air batteries, and water splitting. In this review, rather than overviewing recent progress completely, we aim to give an in-depth digestion of present achievements, focusing on the different roles of nanocarbons and material design principles. The multifunctionalities of nanocarbon substrates(accelerating the electron and mass transport, regulating the incorporation of active components,manipulating electron structures, generating confinement effects, assembly into 3 D free-standing electrodes) and the intrinsic activity of nanocarbon catalysts(multi-heteroatom doping, hierarchical structure,topological defects) are discussed systematically, with perspectives on the further research in this rising research field. This review is inspiring for more insights and methodical research in mechanism understanding, material design, and device optimization, leading to a targeted and high-efficiency development of energy electrocatalysis.
基金supported by the National Natural Science Foundation of China(Nos.U146211821601011)+2 种基金the 973 Program(Grant No.2014CB932102)the Fundamental Research Funds for the Central Universities(buctrc201506PYCC1704)
文摘The explore and development of electrocatalysts have gained significant attention due to their indispensable status in energy storage and conversion systems, such as fuel cells, metal–air batteries and solar water splitting cells. Layered double hydroxides（LDHs） and their derivatives（e.g., transition metal alloys, oxides, sulfides, nitrides and phosphides） have been adopted as catalysts for various electrochemical reactions, such as oxygen reduction, oxygen evolution, hydrogen evolution, and COreduction, which show excellent activity and remarkable durability in electrocatalytic process. In this review, the synthesis strategies, structural characters and electrochemical performances for the LDHs and their derivatives are described. In addition, we also discussed the effect of electronic and geometry structures to their electrocatalytic activity. The further development of high-performance electrocatalysts based on LDHs and their derivatives is covered by both a short summary and future outlook from the viewpoint of the material design and practical application.
基金financially supported by the National Natural Science Foundation of China(No.22008135)the China Postdoctoral Science Foundation(No.2020M670345)。
文摘Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.
基金This study was supported by the National Research Foundation of Korea(NRF-2021R1A2C4001777,NRF-2022M3H4A1A04096482 and RS-2023-00229679),the National Natural Science Foundation of China(No.21965005,52363028)the Natural Science Foundation of Guangxi Province(2021GXNSFAA076001)the Guangxi Technology Base and Talent Subject(GUIKE AD20297039).
文摘Most advanced hydrogen evolution reaction(HER)catalysts show high activity under alkaline conditions.However,the performance deteriorates at a natural and acidic pH,which is often problematic in practical applications.Herein,a rhenium(Re)sulfide–transition-metal dichalcogenide heterojunc-tion catalyst with Re-rich vacancies(NiS_(2)-ReS_(2)-V)has been constructed.The optimized catalyst shows extraordinary electrocatalytic HER performance over a wide range of pH,with ultralow overpotentials of 42,85,and 122 mV under alkaline,acidic,and neutral conditions,respectively.Moreover,the two-electrode system with NiS_(2)-ReS_(2)-V1 as the cathode provides a voltage of 1.73 V at 500 mA cm^(-2),superior to industrial systems.Besides,the open-circuit voltage of a single Zn–H_(2)O cell with NiS_(2)-ReS_(2)-V1 as the cathode can reach an impressive 90.9% of the theoretical value,with a maximum power density of up to 31.6 mW cm^(-2).Moreover,it shows remarkable stability,with sustained discharge for approximately 120 h at 10 mA cm^(-2),significantly outperforming commercial Pt/C catalysts under the same conditions in all aspects.A series of systematic characterizations and theoretical calculations demonstrate that Re vacancies on the heterojunction interface would generate a stronger built-in electric field,which profoundly affects surface charge distribution and subsequently enhances HER performance.
基金supported by a characterization platform for advanced materials funded by the Korea Research Institute of Standards and Science(KRISS-2023-GP2023-0014)the KRISS(Korea Research Institute of Standards and Science)MPI Lab.program。
文摘To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.
文摘Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen was chemically stored by use of a 1,4-benzoquinone/1,4-hydroquinone system, which was used as a recyclable fuel in a commercialised direct methanol fuel cell (DMFC). The electrical output of the cell was about half compared to methanol. The conversion process for water splitting and recombination in a fuel cell was monitored by UV-Vis spectroscopy and compared to a simulated spectrum. Products of side reactions, which lead to a decrease of the overall efficiency, were identified based on UV-Vis investigations. A proof of principle for the use of quinoide systems as a recyclable hydrogen storage system in a photocatalytic water splitting and fuel cell cyclic process was given.
基金supported by the Fundamental Research Funds for the Central Universities(No.HIT.IBRSEM.A.201409)the Program for Innovation Research of Science in Harbin Institute of Technology(PIRS of HIT No.A201418,A201416)+1 种基金the National Natural Science Foundation of China(Nos.21171044 and21371040)the National key Basic Research Program of China(973 Program,No.2013CB632900)
文摘CdS sensitized NiO electrode was used as the photoactive cathode in a photoelectrochemical cell for water splitting,avoiding the use of a sacrificial electron donor.Photocurrent increment under visible light irradiation was observed after integration of[Co（dmgH）_2（4-Me-py）Cl]（1） to the photocathode,suggesting 1 could accept electrons from photoexcited CdS for water reduction and NiO could move the holes in the valence band of CdS to anode for water oxidation.
基金supported by the Ministry of Education(MOE)Tier 1(M4011959 and M4011528)the National Key Research and Development Program of China(2018YFA0209303)+1 种基金the National Natural Science Foundation of China(U1663228 and 51902153)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Although monoclinic WO3 is widely studied as a prototypical photoanode material for solar water splitting,limited success,hitherto,in fabricating WO3 photoanodes that simultaneously demonstrate high efficiency and reproducibility has been realized.The difficulty in controlling both the efficiency and reproducibility is derived from the ever-changing structures/compositions and chemical environments of the precursors,such as peroxytungstic acid and freshly prepared tungstic acid,which render the fabrication processes of the WO3 photoanodes particularly uncontrollable.Herein,a highly reproducible sol-gel process was developed to establish efficient and translucent WO3 photoanodes using a chemically stable ammonium metatungstate precursor.Under standard simulated sunlight of air mass 1.5 G,100 m W cm-2,the WO3 photoanode delivered photocurrent densities of ca.2.05 and2.25 m A cm^-2at 1.23 V versus the reversible hydrogen electrode(RHE),when tested in 1 mol L^-1H2SO4 and CH3SO3H,respectively.Hence,the WO3 photoanodes fabricated herein are one of the WO3 photoanodes with the highest performance ever reported.The reproducibility of the fabrication scheme was evaluated by testing 50 randomly selected WO3 samples in1 mol L^-1H2SO4,which yielded an average photocurrent density of 1.8 m A cm^-2at 1.23 VRHEwith a small standard deviation.Additionally,the effectiveness of the ammonium metatungstate precursor solution was maintained for at least 3weeks,when compared with the associated upper-limit values of peroxytungstic and tungstic acid-based precursors after 3 d.This study presents a key step to the future development of WO3 photoanodes for efficient solar water splitting.
基金Supported by the the National Natural Science Foundation of China(Nos.21572280,21975291,and 61772053)the Natural Science Foundation of Guangdong Province,China(No.2019A1515011640)the Fundamental Research Funds for the Central Universities of China(No.19lgpy12).
文摘A series of novel calix[4]arene metal-free dyes,featuring macrocyclic structure and unique conical confor mation,has been introduced into photoanode-based dye-sensitized electrochemical cell system as photosensitizers.The electrochemical properties of the corresponding sensitized photoanodes were systematically studied in the absence.presence of water oxidation catalyst(WOC).Furthermore,the visible-light-driven overall water-splitting reactions wero conducted by fully assembled devices,obtaining a performance trend of Calix-3>Calix-2 Calix-1.The correspondins device of Calix-3 exhibited the best photoactivity,giving an initial photocurrent density of ca.300 pA/cm^2,an IPEC peak value of ca.9.0%at 365 nm and a wide photo-respond band up to ca.620 nm.The best performance of Calix-3 an be attributed to its most effective light-harvesting ability,best ICT transition property,highest oxidation potentiaand thus best ability of activating WOC.This work offers an inspiration for the application of new-type effective metal-free sensitizers in photocatalytic water-splitting device.
基金supported by the National Natural Science Foundation of China(22179065,21875118,22111530112)the Tianjin Research Innovation Project for Postgraduate Students(2020YJSB143)the Ph.D.Candidate Research Innovation Fund of NKU School of Materials Science and Engineering.
文摘Electrocatalytic water splitting driven by renewable energy input to produce clean hydrogen(H_(2))has been widely considered a prospective approach for a future hydrogen-based society.However,the development of industrial alkaline water electrolyzers is hindered due to their unfavorable thermodynamics with high overpotential for delivering the whole process,caused by sluggish kinetics involving four-electron transfer.Further exploration of water electrolysis with low energy consumption and high efficiency is urgently required to meet the ever-growing energy storage and portfolio demands.This review emphasizes the strategies proposed thus far to pursue high-efficiency water electrolysis systems,including from the aspects of electro-catalysts(from monofunctional to bifunctional),electrode engineering(from powdery to self-supported),energy sources(from nonrenewable to renewable),electrolytes(from pure to hybrid),and cell configurations(from integrated to decoupled).Critical appraisals of the pivotal electrochemistry are highlighted to address the challenges in elevating the overall efficiency of water splitting.Finally,valuable insights for the future development directions and bottlenecks of advanced,sustainable,and high-efficiency water splitting systems are outlined.
文摘A new class of second order accuracy semidiscrete difference schemes is presented for the two-dimensional nonlinear scalar hyperbolic conservation laws. It is based on flux splitting, piecewise linear cell-averaged reconstruction and upwind property in the spatial discretization. By using TVD Runge-Kutta time discretization method, the full discrete scheme is obtained and its MmB property is proved. The extension to the two-dimensionalnonlinear hyperbolic conservation law systems is straightforward by using component-wise manner. The main advantage is simple: no Riemann problem is solved, and so field-by-field decomposition is avoided and the complicated computation is reduced. Numerical results of two-dimensional Euler equations of compressible gas dynamics verify the accuracy and robustness of the method.
文摘Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water‐splitting photoelectrodes.In our previous study,the electrochemical activation of Mo‐doped BiVO_(4) electrodes was ascribed to the removal of MoO_(x) segregations,which are considered to be surface recombination centers for photoinduced electrons and holes.However,this proposed mechanism cannot explain why activated Mo‐doped BiVO_(4) electrodes gradually lose their activity when exposed to air.In this study,based on various characterizations,it is suggested that electrochemical treatment not only removes partial MoO_(x) segregations but also initiates the formation of H_(y)MoO_(x) surface defects,which provide charge transfer channels for photogenerated holes.The charge separation of the Mo‐doped BiVO_(4) electrode was significantly enhanced by these charge transfer channels.This study offers a new insight into the electrochemical activation of Mo‐doped BiVO_(4) photoanodes,and the new concept of surface charge transfer channels,a long overlooked factor,will be valuable for the development of other(photo)electrocatalytic systems.
基金the financial supports from the EPSRC (EP/J000582/1 and EP/F026412/1)Ningbo Municipal People’s Government (3315 Plan and 2014A35001-1)。
文摘This study deals with the optimization of best working conditions in molten melt for the production of hydrogen(H2) gas.Limited research has been carried out on how electrochemical process occurs through steam splitting via molten hydroxide.54 combinations of cathode,anode,temperature and voltage have been investigated for the optimization of best working conditions with molten hydroxide for hydrogen gas production.All these electrochemical investigations were carried out at 225 to 300℃ temperature and 1.5 to 2.5 V applied voltage values.The current efficiency of 90.5,80.0 and 68.6% has been achieved using stainless steel anodic cell with nickel,stainless steel and platinum working cathode respectively.For nickel cathode,an increase in the current directly affected the hydrogen gas flow rate at cathode.It can be hypothesized from the noted results that increase in current is directly proportional to operating temperature and applied voltage.Higher values were noted when the applied voltages increased from 1.5 to 2.5 V at 300℃,the flow rate of hydrogen gas increased from 1.5 to 11.3 cm^(3) min^(-1),1.0 to 13 cm^(3) min^(-1) in case of electrolysis@stainless steel and@graphite anode respectively.It is observed that the current efficiency of stainless steel anodic cell was higher than the graphite anodic cell.Therefore,steam splitting with the help of molten salts has shown an encouraging alternate to current methodology for H2 fuel production.
基金financially supported by the National Key Research and Development Program of China(2018YFB1502503)the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(2018B030322001)+3 种基金the Shenzhen Key Laboratory Project(ZDSYS201603311013489)the Shenzhen Science and Technology Projects for Sustainable Development(KCXFZ202002011010317)the Foundation Research Project of Shenzhen(JCYJ20200109141216566)supported by the Center for Computational Science and Engineering at Southern University of Science and Technology。
文摘The hydrogen evolution reaction(HER)is the cathodic process of water splitting,and its reverse,the hydrogen oxidation reaction(HOR),is the anodic process of an H-Ofuel cell;both play important roles in the development of hydrogen energy.The rational design and scalable fabrication of low-cost and efficient bifunctional catalysts for the HER/HOR are highly desirable.Herein,ultrasmall Mo-Ru nanoalloy(Mo_(0.5)Ru_(3)and Mo_(0.5)Ru_(3))particles uniformly distributed on mesoporous carbon(MPC)were successfully synthesized by a simple method that is easy to scale up for mass production.After the incorporation of Mo atoms,the as-prepared Mo_(0.5)Ru_(3)and Mo_(0.5)Ru_(3)nanoalloys maintain a hexagonal-close-packed crystal structure.In acidic media,Mo_(0.5)Ru_(3)exhibits excellent Pt-like HER and HOR activity,as well as good stability.Density functional theory(DFT)calculations reveal that the H adsorption free energy(ΔG)on the Mo_(0.5)Ru_(3)(001)surface(-0.09 eV)is much closer to zero than that of metallic Ru(-0.22 eV),which contributes to the enhanced catalytic activity.In alkaline media,Mo_(0.5)Ru_(3)also presents outstanding HER and HOR activity,even significantly outperforming Pt/C.The DFT results confirm that optimal binding energies with H*and OH*intermediate species,and low energy barriers in the water dissociation and formation steps,efficiently accelerate the alkaline HER/HOR kinetics of Mo_(0.5)Ru_(3).This study provides a new avenue for the scalable fabrication of high-efficiency bifunctional electrocatalysts for the HER and HOR in both acidic and alkaline media.
基金supported by the National Key R&D Program of China (Nos. 2018YFA0306900 and 2018YFA0209500)the National Natural Science Foundation of China (Nos. 21872114,21972121 and 21908253)+4 种基金the Science and Technology Plan Project of Guangdong Province (No. 2018A030310300)the China Postdoctoral Science Foundation (No. 2020M682616)Donors of the American Chemical Society Petroleum Research Fund for partial support of this research (No. 61155-DNI5)Defense Advanced Research Project Agency (DARPA)the Army Research Office for the financial support (No. W911NF-20-1-0304)。
文摘van der Waals (vdWs) heterostructures based on two-dimensional (2D) materials have become a promising candidate for photoelectrochemical (PEC) catalyst not only because of the freedom in materials design that enable the band-offset construction and facilitate the charge separation. They also provide a platform for the study of various of interface effect in PEC. Here, we report a new kind of mixed-dimensional vdWs heterostructure photoelectrode and investigate the strain enhanced PEC performance at vdWs interfaces. Our heterostructures are composed of 2D n-type MoS_(2) nanosheets and three-dimensional (3D) p-type Cu_(2)O nanorod arrays (NRAs), where Cu_(2)O NRAs introduce periodically strain in the p-n junction interface. We find a promotion of the HER catalytic activities in heterostructure based PEC photoelectrodes using in-situ measurement techniques including the scanning electrochemical cell microscopy and various local spectrum probe measurements. This is attributed to the efficient charge separation at the strained heterointerface. Our results demonstrate an interesting venue for understanding the local interface effects with high spatial resolution, and shed light on design and developing high-efficiency photoelectrodes. 1L MoS_(2)/Cu_(2)O vdWs heterostructure photocathodes were prepared by nanoindentation technology. The effects of strain on promoting charge separation at the heterointerface were verified by the enhanced performances in PEC hydrogen evolution reaction of vdWs heterostructure through scanning electrochemical cell microscopy technique and various local spectrum probe measurements.
基金This work was supported by the National Basic Research Program of China （No. 2014CB932103）, the National Natural Science Foundation of China （Nos. 21301016 and 21473013）, and the Beijing Municipal Natural Science Foundation （No. 2152016）.
文摘The development of high-efficiency electrocatalysts for oxygen evolution reactions （OERs） plays an important role in the water-splitting process. Herein, we report a facile way to obtain two-dimensional （2D） single-unit-cell-thick layered double hydroxide （LDH） nanosheets （NSs, - 1.3 nm） within only 5 min. These nanosheets presented significantly enhanced OER performance compared to bulk LDH systems fabricated using the conventional co-precipitation method. The current strategy further allowed control over the chemical compositions and electrochemical activities of the LDH NSs. For example, CoFe-LDH NSs presented the lowest overpotential of 0.28 V at 10 mA/cm2, and the NiFe-LDHs NSs showed Tafel slopes of 33.4 mV/decade and nearly 100% faradaic efficiency, thus outperforming state-of-the-art IrO2 water electrolysis catalysts. Moreover, positron annihilation lifetime spectroscopy and high-resolution transmission electron microscopy observations confirmed that rich defects and distorted lattices occurred within the 2D LDH NSs, which could supply abundant electrochemically active OER sites. Periodic calculations based on density functional theory （DFT） further showed that the CoFe- and NiFe-LDHs presented very low energy gaps and obvious spin-polarization behavior, which facilitated high electron mobility during the OER process. Therefore, this work presents a combined experimental and theoretical study on 2D single-unit-cell-thick LDH NSs with high OER activities, which have potential application in water splitting for renewable energy.
