This study introduces an innovative composite cathode catalyst layer(CCL)design for proton exchange membrane fuel cells(PEMFCs),combining Pt-supported by Vulcan carbon(Pt/V)and Ketjenblack carbon(Pt/KB)to overcome mas...This study introduces an innovative composite cathode catalyst layer(CCL)design for proton exchange membrane fuel cells(PEMFCs),combining Pt-supported by Vulcan carbon(Pt/V)and Ketjenblack carbon(Pt/KB)to overcome mass transport limitations and ionomer-induced catalyst poisoning.The composite architecture strategically positions Pt/V layer with lower ionomer-to-carbon ratio(I/C=0.6)near the proton exchange membrane to maximize surface Pt accessibility and oxygen transport efficiency,whereas Pt/KB layer(I/C=0.9)adjacent to the gas diffusion layer leverages its porous structure to shield Pt from sulfonate group poisoning and enhance proton conduction under low-humidity conditions.This synergistic carbon support engineering achieves a balance between reactant accessibility and catalyst utilization,as demonstrated by improved power density,reduced transport resistance,and higher Pt utilization under dry conditions.These findings establish a new paradigm for low-Pt CCL design through rational carbon support hybridization and ionomer gradient engineering,offering a scalable solution for high-performance PEMFCs in energy-critical applications.展开更多
The catalyst layer is an essential component of fuel cells,exerting a decisive influence on performance,particularly under degradation processes.Characterization derived from accelerated stress tests(ASTs)provide valu...The catalyst layer is an essential component of fuel cells,exerting a decisive influence on performance,particularly under degradation processes.Characterization derived from accelerated stress tests(ASTs)provide valuable insights into the long-term degradation from the perspective of changes in physical and chemical properties,thereby offering a scientific foundation for evaluating advanced materials and strategies.In this review,multidimensional and multi-characterization application scenarios based on ASTs data are systematically summarized.Firstly,the degradation mechanism of catalyst layer(CL)under AST conditions is discussed,with an emphasis on platinum aging and carbon support corrosion.In addition,electrochemical and microphysical characterization tools applicable to different AST test protocols,such as electrochemical surface area(ECSA),electrochemical impedance spectrum(EIS)mapping combined with distribution of relaxation times(DRT),and microscopic physical evolution and tracking techniques for each internal chemical component,are also presented in detail.Finally,through the existing research progress and hotspots,the application prospect of data fusion is elaborated and the important research direction of material optimization and performance prediction based on AST data is emphasized,aiming to provide insights into the study of catalytic layer degradation in fuel cells and promote the continuous development of the field.展开更多
Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure ...Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.展开更多
Mass transport is crucial to the performance of proton exchange membrane fuel cells,especially at high current densities.Generally,the oxygen and the generated water share same transmission medium but move towards opp...Mass transport is crucial to the performance of proton exchange membrane fuel cells,especially at high current densities.Generally,the oxygen and the generated water share same transmission medium but move towards opposite direction,which leads to serious mass transfer problems.Herein,a series of patterned catalyst layer were prepared with a simple one-step impressing method using nylon sieves as templates.With grooves 100μm in width and 8μm in depth on the surface of cathode catalyst layer,the maximum power density of fuel cell increases by 10%without any additional durability loss while maintaining a similar electrochemical surface area.The concentration contours calculated by finite element analysis reveal that the grooves built on the surface of catalyst layer serve to accumulate the water nearby while oxygen tends to transfer through relatively convex region,which results from capillary pressure difference caused by the pore structure difference between the two regions.The separation of oxidant gas and generated water avoids mass confliction thus boosts mass transport efficiency.展开更多
An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the ...An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes. In this paper, a novel process of the catalyst layers was introduced and investigated. A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode （GCE） to form a thin carbon layer. Then Pt particles were deposited on the surface by reducing hexachloroplatinic （IV） acid hexahydrate with methanoic acid. SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method. The Pt nanowires grown are in the size of 3 nm （diameter） x l0 nm （length） by high solution TEM image. The novel catalyst layer was characterized by cyclic voltammetry （CV） and scanning electron microscope （SEM） as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering. The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants （oxygen or hydrogen）.展开更多
The catalyst layer(CL)is the core component in determining the electrical-thermal-water performance and cost of proton exchange membrane fuel cell(PEMFC).Systemic analysis and rapid prediction tools are required to im...The catalyst layer(CL)is the core component in determining the electrical-thermal-water performance and cost of proton exchange membrane fuel cell(PEMFC).Systemic analysis and rapid prediction tools are required to improve the design efficiency of CL.In this study,a 3D multi-phase model integrated with the multi-level agglomerate model for CL is developed to describe the heat and mass transfer processes inside PEMFC.Moreover,a research framework combining the response surface method(RSM)and artificial neural network(ANN)model is proposed to conduct a quantitative analysis,and further a rapid and accurate prediction.With the help of this research framework,the effects of CL composition on the electrical-thermal-water performance of PEMFC are investigated.The results show that the mass of platinum,the mass of carbon,and the volume fraction of dry ionomer has a significant impact on the electrical-thermal-water performance.At the selected points,the sensitivity of the decision variables is ranked:volume fraction of dry ionomer>mass of platinum>mass of carbon>agglomerate radius.In particular,the sensitivity of the volume fraction of dry ionomer is over 50%at these points.Besides,the comparison results show that the ANN model could implement a more rapid and accurate prediction than the RSM model based on the same sample set.This in-depth study is beneficial to provide feasible guidance for high-performance CL design.展开更多
The electrode ionomer plays a crucial role in the catalyst layer(CL) of a proton-exchange membrane fuel cell(PEMFC) and is closely associated with the proton conduction and gas transport properties,structural stabilit...The electrode ionomer plays a crucial role in the catalyst layer(CL) of a proton-exchange membrane fuel cell(PEMFC) and is closely associated with the proton conduction and gas transport properties,structural stability,and water management capability.In this review,we discuss the CL structural characteristics and highlight the latest advancements in ionomer material research.Additionally,we comprehensively introduce the design concepts and exceptional performances of porous electrode ionomers,elaborate on their structural properties and functions within the fuel cell CL,and investigate their effect on the CL microstructure and performance.Finally,we present a prospective evaluation of the developments in the electrode ionomer for fabricating CL,offering valuable insights for designing and synthesizing more efficient electrode ionomer materials.By addressing these facets,this review contributes to a comprehensive understanding of the role and potential of electrode ionomers for enhancing PEMFC performance.展开更多
To evaluate the H_(2)O_(2)‐tolerance of non‐Pt oxygen reduction reaction(ORR)catalysts as well as in‐vestigate the H_(2)O_(2)‐induced decay mechanism,the selection of an appropriate H_(2)O_(2) concentration is a p...To evaluate the H_(2)O_(2)‐tolerance of non‐Pt oxygen reduction reaction(ORR)catalysts as well as in‐vestigate the H_(2)O_(2)‐induced decay mechanism,the selection of an appropriate H_(2)O_(2) concentration is a prerequisite.However,the concentration criterion is still unclear because of the lack of in‐operando methods to determine the actual concentration of H_(2)O_(2) in fuel cell catalyst layers.In this work,an electrochemical probe method was successfully established to in‐operando monitor the H_(2)O_(2) in non‐Pt catalyst layers for the first time.The local concentration of H_(2)O_(2) was revealed to reach 17 mmol/L,which is one order of magnitude higher than that under aqueous electrodes test conditions.Powered by the new knowledge,a concentration criterion of at least 17 mmol/L is suggested.This work fills in the large gap between aqueous electrode tests and the real fuel cell working conditions,and highlights the importance of in‐operando monitoring methods.展开更多
The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks...The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology.Thus,the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers.The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction(HOR)and oxygen reduction reaction(ORR)that are taking place in the catalyst layers consisting of Platinum-based and Platinum-non noble metals.For this purpose,studies from the literature are presented and analyzed by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional ones.Furthermore,an economic analysis of the main platinum group metals(PGMs)such as Platinum,Palladium and Ruthenium is introduced by presenting the economic trends for the last decade.展开更多
Fabrication of novel electrode architectures with nanostructured ultrathin catalyst layers is an effective strategy to improve catalyst utilization and enhance mass transport for polymer electrolyte membrane fuel cell...Fabrication of novel electrode architectures with nanostructured ultrathin catalyst layers is an effective strategy to improve catalyst utilization and enhance mass transport for polymer electrolyte membrane fuel cells (PEMFCs).Herein,we report the design and construction of a nanostructured ultrathin catalyst layer with ordered Pt nanotube arrays,which were obtained by a hard-template strategy based on ZnO,via hydrothermal synthesis and magnetron sputtering for PEMFC application.Because of the crystallographically preferential growth of Pt (111) facets,which was attributed to the structural effects of ZnO nanoarrays on the Pt nanotubes,the catalyst layers exhibit obviously higher electrochemical activity with remarkable enhancement of specific activity and mass transport compared with the state-of-the-art randomly distributed Pt/C catalyst layer.The PEMFC fabricated with the as-prepared catalyst layer composed of optimized Pt nanotubes with an average diameter of 90(±10) nm shows excellent performance with a peak power density of 6.0W/mgPt at 1 A/cm^2,which is 11.6%greater than that of the conventional Pt/C electrode.展开更多
Appropriate hydrophobicity and porosity of the proton-exchange membrane fuel cell(PEMFC)cathode catalyst layer(CCL)are essential for efficient charge and mass transport.In this study,the effects of the CCL hydrophobic...Appropriate hydrophobicity and porosity of the proton-exchange membrane fuel cell(PEMFC)cathode catalyst layer(CCL)are essential for efficient charge and mass transport.In this study,the effects of the CCL hydrophobicity and porosity on PEMFC performance were comprehensively investigated.Compared to a normal CCL,a cathode hydrophobic duallayer catalyst structure(with a 2:1 Pt loading ratio between the inner and outer layers and 9.3%polytetrafluoroethylene(PTFE)in the outer layer)exhibited a 29.8%increase in power density.Among the tested pore-forming agents,ammonium bicarbonate(NH_4HCO_(3))was the most suitable because of its low pyrolysis temperature.The maximum power density of the CCL with a porous structure(prepared with a Pt/C:NH_4HCO_(3)mass ratio of 1:3)was 38.3%higher than that of the normal CCL.By simultaneously optimizing the pore structure and hydrophobicity of the CCL,the maximum power density of the cathode hydrophobic dual-layer CCL(DCL)with pores showed a 44.7%increase compared to that of the normal CCL.This study demonstrates for the first time that simultaneously optimizing cathode porosity and hydrophobicity can enhance PEMFC performance.展开更多
Electrochemical CO_(2)reduction(CO_(2)RR)is a promising technology for mitigating global climate change.The catalyst layer(CL),where the reduction reaction occurs,plays a pivotal role in determining mass transport and...Electrochemical CO_(2)reduction(CO_(2)RR)is a promising technology for mitigating global climate change.The catalyst layer(CL),where the reduction reaction occurs,plays a pivotal role in determining mass transport and electrochemical performance.However,accurately characterizing local structures and quantifying mass transport remains a significant challenge.To address these limitations,a systematic characterization framework based on deep learning(DL)is proposed.Five semantic segmentation models,including Segformer and DeepLabV3plus,were compared with conventional image processing techniques,among which DeepLabV3plus achieved the highest segmentation accuracy(>91.29%),significantly outperforming traditional thresholding methods(72.35%–77.42%).Experimental validation via mercury intrusion porosimetry(MIP)confirmed its capability to precisely extract key structural parameters,such as porosity and pore size distribution.Furthermore,a series of ionomer content gradient experiments revealed that a CL with an ionomer/catalyst(I/C)ratio of 0.2 had the optimal pore network structure.Numerical simulations and electrochemical tests demonstrated that this CL enabled a twofold increase in gas diffusion distance,thereby promoting long-range mass transport and significantly enhancing CO production rates.This work establishes a multi-scale analysis framework integrating“structural characterization,mass transport simulation,and performance validation,”offering both theoretical insights and practical guidance for the rational design of CO_(2)RR CLs.展开更多
Developing cathode catalyst layers(CCL)with efficient mass transport capability is crucial to developing ultra-low Pt loading(<50μg·cm^(-2))proton exchange membrane fuel cells(PEMFCs).Herein,CCLs with various...Developing cathode catalyst layers(CCL)with efficient mass transport capability is crucial to developing ultra-low Pt loading(<50μg·cm^(-2))proton exchange membrane fuel cells(PEMFCs).Herein,CCLs with various pore distributions were constructed by depositing Pt onto the integrated carbonaceous films consisting of carbon nanoparticles(CNs),three-dimensional(3D)graphene nanosheets(GNs),and nanocomposites of CNs and GNs(CNs-GNs),respectively.The hierarchical mesoporous pore distributions of CCLs strongly affect the effective exposure of Pt active sites,proton-transfer resistance,and oxygen mass transport efficiencies related to Knudsen diffusion and local resistance at the Pt/ionomer interface.The CCL with Pt/CNs-GNs(50.0μgPt·cm^(-2))features a unique tri-modal pore distribution concentrated at 10.2,20.4,and 43.7 nm,providing efficient three-phase boundaries with a significantly higher active surface area of 49.67 m2·g^(-1),lower oxygen transport resistance and proton resistance of down to 18.68 s·m^(-1) and 0.0603Ω·cm^(2),compared with Pt/CNs(31.48 m^(2)·g^(-1),41.17 s·m^(-1),and 0.0702Ω·cm^(2))with a single-modal pore distribution at 9.5 nm and Pt/GNs(38.21 m^(2)·g^(-1),33.40 s·m^(-1),and 0.0654Ω·cm^(2))with a bi-modal pore distribution at 9.8 and 20.9 nm.Correspondingly,the cell with Pt/CNs-GNs delivers a high power output of up to 1.01 W·cm^(-2) and presents a high durability that satisfies the 2025 targets set by the U.S.Department of Energy.This work provides new insights into the critical role of hierarchically mesoporous pore distribution of CCL for constructing high-performance PEMFCs with ultra-low Pt loading<50μg·cm^(-2).展开更多
To achieve palm oil conversion along with a high yield of long‐chain alkane,a series of NiFe layered double oxide catalysts were prepared and employed in the deoxygenation of palm oil.The layered structure of these c...To achieve palm oil conversion along with a high yield of long‐chain alkane,a series of NiFe layered double oxide catalysts were prepared and employed in the deoxygenation of palm oil.The layered structure of these catalysts was confirmed by XRD and SEM analyses,and Ni and Fe species existed primarily in the forms of Ni^(2+)and Fe^(3+),respectively.It was found that Ni/Fe molar ratio influenced the H_(2)reducibility and surface properties of NiFe catalysts.Specifically,Ni_(2)Fe‐LDO and Ni_(3)Fe‐LDO exhibited higher reducibility under H_(2)atmosphere.Moreover,the Ni_(2)Fe‐LDO catalyst contained a higher concentration of surface oxygen species(Osurf).Deoxygenation results demonstrated that the Ni_(2)Fe‐LDO catalyst achieved superior palm oil conversion,higher liquid product yield and enhanced selectivity toward C_(15)–C_(18)hydrocarbons compared to other catalysts.This improved performance was attributed to its higher hydrogen dissociation activity and enhanced adsorption capacity for palm oil molecules.Furthermore,reaction condition studies revealed that palm oil was completely converted,yielding 86.8%liquid product with 81.8%selectivity of C_(15)–C_(18)hydrocarbons at 350℃under 7 MPa H_(2)pressure.This finding provides an insight into the development of efficient catalysts for the deoxygenation of fatty compounds to biofuels.展开更多
Catalyst layer(CL)is the core component of proton exchange membrane(PEM)fuel cells,which determines the performance,durability,and cost.However,difficulties remain for a thorough understanding of the CLs’inhomogeneou...Catalyst layer(CL)is the core component of proton exchange membrane(PEM)fuel cells,which determines the performance,durability,and cost.However,difficulties remain for a thorough understanding of the CLs’inhomogeneous structure,and its impact on the physicochemical and electrochemical properties,operating performance,and durability.The inhomogeneous structure of the CLs is formed during the manufacturing process,which is sensitive to the associated materials,composi-tion,fabrication methods,procedures,and conditions.The state-of-the-art visualization and characterization techniques are crucial to examine the CL structure.The structure-dependent physicochemical and electrochemical properties are then thoroughly scrutinized in terms of fundamental concepts,theories,and recent progress in advanced experimental techniques.The relation between the CL structure and the associated effective properties is also examined based on experimental and theoretical findings.Recent studies indicated that the CL inhomogeneous structure also strongly affects the performance and degradation of the whole fuel cell,and thus,the interconnection between the fuel cell performance,failure modes,and CL structure is comprehensively reviewed.An analytical model is established to understand the effect of the CL structure on the effective properties,performance,and durability of the PEM fuel cells.Finally,the challenges and prospects of the CL structure-associated studies are highlighted for the development of high-performing PEM fuel cells.展开更多
The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most ...The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most expensive component due to the use of a Pt catalyst. Apart from the ORR itself, the species transport to and from the reactive sites determines the performance of the PEFC. The effective transport properties of the species in the CCL depend on its nanostructure. Therefore a three-dimensional reconstruction of the CCL is required. A series of two-dimensional images was obtained from focused ion beam- scanning electron microscope （FIB-SEM） imaging and a segmentation method for the two-dimensional images has been developed. The pore size distribution （PSD） was calculated for the three-dimensional geometry. The influence of the alignment and the anisotropic pixel size on the PSD has been investigated. Pores were found in the range between 5 nm and 205 nm. Evaluation of the Knudsen number showed that gas transport in the CCL is governed by the transition flow regime. The liquid water transport can be described within continuum hydrodynamics by including suitable slip flow boundary conditions.展开更多
A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells(PEMFC)was established by Monte Carlo method.The model takes into account all the four components in a typical PEMFC cat...A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells(PEMFC)was established by Monte Carlo method.The model takes into account all the four components in a typical PEMFC catalyst layer:platinum(Pt),carbon,ionomer and pore.The elemental voxels in the lattice were setfine enough so that each average sized Pt particulate in Pt/C catalyst can be represented.Catalyst utilization in the modeled catalyst layer was calculated by counting up the number of facets of Pt voxels where“three phase contact”are met.The effects of some factors,including porosity,ionomer content,Pt/C particle size and Pt weight percentage in the Pt/C catalyst,on catalyst utilization were investigated and discussed.展开更多
The effective management of oxygen transport resistance(OTR)within the cathode catalyst layer(CCL)is crucial for achieving a high catalyst performance at low platinum(Pt)loading.Over the past two decades,significant a...The effective management of oxygen transport resistance(OTR)within the cathode catalyst layer(CCL)is crucial for achieving a high catalyst performance at low platinum(Pt)loading.Over the past two decades,significant advancements have been made in the development of various high active platinum-based catalysts,aiming at enhancing oxygen mass transport and the oxygen reduction reaction(ORR).However,experimental investigations of transport processes in porous media are often computational costs and restrained by limitations in in-situ measurement capabilities,as well as spatial and temporal resolution.Fortunately,numerical simulation provides a valuable alternative for unveiling the intricate relationship between local transport properties and overall cell performance that remain unresolved or uncoupled through experimental approach.In this review,we elucidate the primary experimental and numerical efforts undertaken to improve OTR.We consolidate the available literature on OTR values and perform a quantitative comparison of the effectiveness of different strategies in mitigating OTR.Furthermore,we analyze the intrinsic limitations and challenges associated with current experimental and numerical methods.Finally,we outline future prospect for advancements in both experimental techniques and modelling methods.展开更多
A porous ceramic support is designed as a multi-functional independent catalyst layer for solid oxide fuel cells(SOFCs)running on liquid hydrocarbon fuel.The layer consists of a highly porous Ce_(0.9)Ca_(0.1)O_(2−δ)c...A porous ceramic support is designed as a multi-functional independent catalyst layer for solid oxide fuel cells(SOFCs)running on liquid hydrocarbon fuel.The layer consists of a highly porous Ce_(0.9)Ca_(0.1)O_(2−δ)ceramic backbone and active NiMo catalysts,which could be integrated into the conventional Ni metal containing the anode for internal reforming of the hydrocarbon fuel.Compared to conventional catalyst layers sintered on the anodes,this independent catalyst layer could be simply assembled on top of the anode without additional sintering,thereby avoiding the mismatch of the thermal expansion coefficient between the catalyst layer and the anode and improving stability of a single cell.Moreover,a current collector layer could be inserted between the catalyst and the anode to enhance current collection efficiency and electrochemical performance of the single cell.At 750℃,the independent catalyst layer displays high activity towards the catalytic decomposition of methanol,and the single cell could achieve the maximum power density of 400–500 mW·cm^(−2)in dry methanol.Furthermore,by employing the independent catalyst layer,the single cell offers additional in-situ catalyst regeneration capability under the methanol operation mode.Feeding 10 mL·min−1 air into an anode channel for 5 min is found to be effective to burn out carbon species in the catalyst layer,which reduces the degradation rate of the cell voltage by orders of magnitude from 2.6 to 0.024 mV·h−1 during the operation of 360 h in dry methanol.The results demonstrate the significance of the independent catalyst layer design for direct internal reforming methanol fuel cells.展开更多
PtRu supported on TiO2-embedded carbon nanofibers(PtRu/TECNF),which was recently reported as a highly-active catalyst for methanol oxidation,was applied to a direct methanol fuel cell(DMFC),and the power generation pe...PtRu supported on TiO2-embedded carbon nanofibers(PtRu/TECNF),which was recently reported as a highly-active catalyst for methanol oxidation,was applied to a direct methanol fuel cell(DMFC),and the power generation performance was compared to that using the commercial PtRu/C.Before the comparison,the effect of the catalyst loading on the power density of the DMFC was investigated using PtRu(18 wt%)/TECNF.The DMFC power density showed a maximum at about a 1.5 mg cm2 PtRu loading that corresponds to about an 80 mm layer thickness.A catalyst layer thicker than this value reduced the power density probably due to the concentration overvoltage.The PtRu content in the PtRu/TECNF was then increased to 30 wt%or more to reduce the layer thickness and to increase the power density.The DMFC performance was compared to that of different anode catalysts at a 1 mg cm2 PtRu loading.The power density was maximized using the PtRu30 wt%/TECNF,which showed a 173 mW cm2 at 353 K and had 66 mm layer thick,that was 26%higher than that of commercial PtRu/C.The current–voltage curve of the DMFC with the PtRu/TECNF suggested an improved mass transport overvoltage,but a little improvement in the activation one despite using the catalyst with about a 2 times higher activity compared to that of the commercial PtRu/C.This was attributed to the lower Pt utilization of the nanofiber catalyst layer.展开更多
基金financially supported by National Natural Science Foundation of China(22202124 and UA22A20429)Shanxi Scholarship Council of China(2023-008 and 2023-009)+4 种基金Shanxi Outstanding Project Selection and Support Program for Overseas Scientific and Technological Activities(20230002)Science and Technology Innovation Teams of Shanxi Province(202304051001023)the Key Research and Development Program of Shanxi Province(No.202302060301009)Qingdao New Energy Shandong Laboratory Open Project(QNESL OP)Shandong Provincial Natural Science Foundation(Nos.ZR2024QB175 and ZR2023LFG005).
文摘This study introduces an innovative composite cathode catalyst layer(CCL)design for proton exchange membrane fuel cells(PEMFCs),combining Pt-supported by Vulcan carbon(Pt/V)and Ketjenblack carbon(Pt/KB)to overcome mass transport limitations and ionomer-induced catalyst poisoning.The composite architecture strategically positions Pt/V layer with lower ionomer-to-carbon ratio(I/C=0.6)near the proton exchange membrane to maximize surface Pt accessibility and oxygen transport efficiency,whereas Pt/KB layer(I/C=0.9)adjacent to the gas diffusion layer leverages its porous structure to shield Pt from sulfonate group poisoning and enhance proton conduction under low-humidity conditions.This synergistic carbon support engineering achieves a balance between reactant accessibility and catalyst utilization,as demonstrated by improved power density,reduced transport resistance,and higher Pt utilization under dry conditions.These findings establish a new paradigm for low-Pt CCL design through rational carbon support hybridization and ionomer gradient engineering,offering a scalable solution for high-performance PEMFCs in energy-critical applications.
基金supported by National Natural Science Foundation of China(22279091)Fundamental Funds for the Central Universities。
文摘The catalyst layer is an essential component of fuel cells,exerting a decisive influence on performance,particularly under degradation processes.Characterization derived from accelerated stress tests(ASTs)provide valuable insights into the long-term degradation from the perspective of changes in physical and chemical properties,thereby offering a scientific foundation for evaluating advanced materials and strategies.In this review,multidimensional and multi-characterization application scenarios based on ASTs data are systematically summarized.Firstly,the degradation mechanism of catalyst layer(CL)under AST conditions is discussed,with an emphasis on platinum aging and carbon support corrosion.In addition,electrochemical and microphysical characterization tools applicable to different AST test protocols,such as electrochemical surface area(ECSA),electrochemical impedance spectrum(EIS)mapping combined with distribution of relaxation times(DRT),and microscopic physical evolution and tracking techniques for each internal chemical component,are also presented in detail.Finally,through the existing research progress and hotspots,the application prospect of data fusion is elaborated and the important research direction of material optimization and performance prediction based on AST data is emphasized,aiming to provide insights into the study of catalytic layer degradation in fuel cells and promote the continuous development of the field.
基金finically supported by the National Natural Science Foundation of China(22075055)the Guangxi Science and Technology Project(AB16380030)the Innovation Project of Guangxi Graduate Education(YCSW2020052)。
文摘Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.
基金supported by the National Natural Science Foundation of China(21838003,91834301)the Shanghai Scientific and Technological Innovation Project(18JC1410600,19JC1410400)+2 种基金the Social Development Program of Shanghai(17DZ1200900)the Innovation Program of Shanghai Municipal Education Commissionthe Fundamental Research Funds for the Central Universities(222201718002)。
文摘Mass transport is crucial to the performance of proton exchange membrane fuel cells,especially at high current densities.Generally,the oxygen and the generated water share same transmission medium but move towards opposite direction,which leads to serious mass transfer problems.Herein,a series of patterned catalyst layer were prepared with a simple one-step impressing method using nylon sieves as templates.With grooves 100μm in width and 8μm in depth on the surface of cathode catalyst layer,the maximum power density of fuel cell increases by 10%without any additional durability loss while maintaining a similar electrochemical surface area.The concentration contours calculated by finite element analysis reveal that the grooves built on the surface of catalyst layer serve to accumulate the water nearby while oxygen tends to transfer through relatively convex region,which results from capillary pressure difference caused by the pore structure difference between the two regions.The separation of oxidant gas and generated water avoids mass confliction thus boosts mass transport efficiency.
基金supported by the Royal Academy of Engineering,United Kingdom
文摘An extensive study has been conducted on the proton exchange membrane fuel cells （PEMFCs） with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes. In this paper, a novel process of the catalyst layers was introduced and investigated. A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode （GCE） to form a thin carbon layer. Then Pt particles were deposited on the surface by reducing hexachloroplatinic （IV） acid hexahydrate with methanoic acid. SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method. The Pt nanowires grown are in the size of 3 nm （diameter） x l0 nm （length） by high solution TEM image. The novel catalyst layer was characterized by cyclic voltammetry （CV） and scanning electron microscope （SEM） as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering. The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants （oxygen or hydrogen）.
基金financially supported by the National Key R&D Program of China (2022YFE0101300)the National Natural Science Foundation of China (52176203)。
文摘The catalyst layer(CL)is the core component in determining the electrical-thermal-water performance and cost of proton exchange membrane fuel cell(PEMFC).Systemic analysis and rapid prediction tools are required to improve the design efficiency of CL.In this study,a 3D multi-phase model integrated with the multi-level agglomerate model for CL is developed to describe the heat and mass transfer processes inside PEMFC.Moreover,a research framework combining the response surface method(RSM)and artificial neural network(ANN)model is proposed to conduct a quantitative analysis,and further a rapid and accurate prediction.With the help of this research framework,the effects of CL composition on the electrical-thermal-water performance of PEMFC are investigated.The results show that the mass of platinum,the mass of carbon,and the volume fraction of dry ionomer has a significant impact on the electrical-thermal-water performance.At the selected points,the sensitivity of the decision variables is ranked:volume fraction of dry ionomer>mass of platinum>mass of carbon>agglomerate radius.In particular,the sensitivity of the volume fraction of dry ionomer is over 50%at these points.Besides,the comparison results show that the ANN model could implement a more rapid and accurate prediction than the RSM model based on the same sample set.This in-depth study is beneficial to provide feasible guidance for high-performance CL design.
基金supported by the National Natu-ral Science Foundation of China(Nos.21625102,21971017,and 22102008)National Key Research and Development Program of China(No.2020YFB1506300)Postdoctoral Fund of China(Nos.2020T130055 and 2020M670143).
文摘The electrode ionomer plays a crucial role in the catalyst layer(CL) of a proton-exchange membrane fuel cell(PEMFC) and is closely associated with the proton conduction and gas transport properties,structural stability,and water management capability.In this review,we discuss the CL structural characteristics and highlight the latest advancements in ionomer material research.Additionally,we comprehensively introduce the design concepts and exceptional performances of porous electrode ionomers,elaborate on their structural properties and functions within the fuel cell CL,and investigate their effect on the CL microstructure and performance.Finally,we present a prospective evaluation of the developments in the electrode ionomer for fabricating CL,offering valuable insights for designing and synthesizing more efficient electrode ionomer materials.By addressing these facets,this review contributes to a comprehensive understanding of the role and potential of electrode ionomers for enhancing PEMFC performance.
文摘To evaluate the H_(2)O_(2)‐tolerance of non‐Pt oxygen reduction reaction(ORR)catalysts as well as in‐vestigate the H_(2)O_(2)‐induced decay mechanism,the selection of an appropriate H_(2)O_(2) concentration is a prerequisite.However,the concentration criterion is still unclear because of the lack of in‐operando methods to determine the actual concentration of H_(2)O_(2) in fuel cell catalyst layers.In this work,an electrochemical probe method was successfully established to in‐operando monitor the H_(2)O_(2) in non‐Pt catalyst layers for the first time.The local concentration of H_(2)O_(2) was revealed to reach 17 mmol/L,which is one order of magnitude higher than that under aqueous electrodes test conditions.Powered by the new knowledge,a concentration criterion of at least 17 mmol/L is suggested.This work fills in the large gap between aqueous electrode tests and the real fuel cell working conditions,and highlights the importance of in‐operando monitoring methods.
文摘The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology.Thus,the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers.The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction(HOR)and oxygen reduction reaction(ORR)that are taking place in the catalyst layers consisting of Platinum-based and Platinum-non noble metals.For this purpose,studies from the literature are presented and analyzed by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional ones.Furthermore,an economic analysis of the main platinum group metals(PGMs)such as Platinum,Palladium and Ruthenium is introduced by presenting the economic trends for the last decade.
基金financially supported by the National Natural Science Foundation of China(NSFC,Grant no.21503228)the Transformational Technologies for Clean Energy and Demonstration,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant no.XDA21090203)。
文摘Fabrication of novel electrode architectures with nanostructured ultrathin catalyst layers is an effective strategy to improve catalyst utilization and enhance mass transport for polymer electrolyte membrane fuel cells (PEMFCs).Herein,we report the design and construction of a nanostructured ultrathin catalyst layer with ordered Pt nanotube arrays,which were obtained by a hard-template strategy based on ZnO,via hydrothermal synthesis and magnetron sputtering for PEMFC application.Because of the crystallographically preferential growth of Pt (111) facets,which was attributed to the structural effects of ZnO nanoarrays on the Pt nanotubes,the catalyst layers exhibit obviously higher electrochemical activity with remarkable enhancement of specific activity and mass transport compared with the state-of-the-art randomly distributed Pt/C catalyst layer.The PEMFC fabricated with the as-prepared catalyst layer composed of optimized Pt nanotubes with an average diameter of 90(±10) nm shows excellent performance with a peak power density of 6.0W/mgPt at 1 A/cm^2,which is 11.6%greater than that of the conventional Pt/C electrode.
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(Grant No.52488201)the National Key R&D Program of China(Grant No.2021YFF0500504)the Fundamental Research Funds for the Central Universities。
文摘Appropriate hydrophobicity and porosity of the proton-exchange membrane fuel cell(PEMFC)cathode catalyst layer(CCL)are essential for efficient charge and mass transport.In this study,the effects of the CCL hydrophobicity and porosity on PEMFC performance were comprehensively investigated.Compared to a normal CCL,a cathode hydrophobic duallayer catalyst structure(with a 2:1 Pt loading ratio between the inner and outer layers and 9.3%polytetrafluoroethylene(PTFE)in the outer layer)exhibited a 29.8%increase in power density.Among the tested pore-forming agents,ammonium bicarbonate(NH_4HCO_(3))was the most suitable because of its low pyrolysis temperature.The maximum power density of the CCL with a porous structure(prepared with a Pt/C:NH_4HCO_(3)mass ratio of 1:3)was 38.3%higher than that of the normal CCL.By simultaneously optimizing the pore structure and hydrophobicity of the CCL,the maximum power density of the cathode hydrophobic dual-layer CCL(DCL)with pores showed a 44.7%increase compared to that of the normal CCL.This study demonstrates for the first time that simultaneously optimizing cathode porosity and hydrophobicity can enhance PEMFC performance.
基金supported by the National Natural Science Foundation of China(Grant No.52394204)the Shanghai Municipal Science and Technology Major Project,and Shanghai Jiao Tong University Decision Consulting,China(JCZXSJB2024-12).
文摘Electrochemical CO_(2)reduction(CO_(2)RR)is a promising technology for mitigating global climate change.The catalyst layer(CL),where the reduction reaction occurs,plays a pivotal role in determining mass transport and electrochemical performance.However,accurately characterizing local structures and quantifying mass transport remains a significant challenge.To address these limitations,a systematic characterization framework based on deep learning(DL)is proposed.Five semantic segmentation models,including Segformer and DeepLabV3plus,were compared with conventional image processing techniques,among which DeepLabV3plus achieved the highest segmentation accuracy(>91.29%),significantly outperforming traditional thresholding methods(72.35%–77.42%).Experimental validation via mercury intrusion porosimetry(MIP)confirmed its capability to precisely extract key structural parameters,such as porosity and pore size distribution.Furthermore,a series of ionomer content gradient experiments revealed that a CL with an ionomer/catalyst(I/C)ratio of 0.2 had the optimal pore network structure.Numerical simulations and electrochemical tests demonstrated that this CL enabled a twofold increase in gas diffusion distance,thereby promoting long-range mass transport and significantly enhancing CO production rates.This work establishes a multi-scale analysis framework integrating“structural characterization,mass transport simulation,and performance validation,”offering both theoretical insights and practical guidance for the rational design of CO_(2)RR CLs.
基金supported by the National Natural Science Foundation of China(No.22379031)the Guangxi Science and Technology Project of China(No.AB16380030)。
文摘Developing cathode catalyst layers(CCL)with efficient mass transport capability is crucial to developing ultra-low Pt loading(<50μg·cm^(-2))proton exchange membrane fuel cells(PEMFCs).Herein,CCLs with various pore distributions were constructed by depositing Pt onto the integrated carbonaceous films consisting of carbon nanoparticles(CNs),three-dimensional(3D)graphene nanosheets(GNs),and nanocomposites of CNs and GNs(CNs-GNs),respectively.The hierarchical mesoporous pore distributions of CCLs strongly affect the effective exposure of Pt active sites,proton-transfer resistance,and oxygen mass transport efficiencies related to Knudsen diffusion and local resistance at the Pt/ionomer interface.The CCL with Pt/CNs-GNs(50.0μgPt·cm^(-2))features a unique tri-modal pore distribution concentrated at 10.2,20.4,and 43.7 nm,providing efficient three-phase boundaries with a significantly higher active surface area of 49.67 m2·g^(-1),lower oxygen transport resistance and proton resistance of down to 18.68 s·m^(-1) and 0.0603Ω·cm^(2),compared with Pt/CNs(31.48 m^(2)·g^(-1),41.17 s·m^(-1),and 0.0702Ω·cm^(2))with a single-modal pore distribution at 9.5 nm and Pt/GNs(38.21 m^(2)·g^(-1),33.40 s·m^(-1),and 0.0654Ω·cm^(2))with a bi-modal pore distribution at 9.8 and 20.9 nm.Correspondingly,the cell with Pt/CNs-GNs delivers a high power output of up to 1.01 W·cm^(-2) and presents a high durability that satisfies the 2025 targets set by the U.S.Department of Energy.This work provides new insights into the critical role of hierarchically mesoporous pore distribution of CCL for constructing high-performance PEMFCs with ultra-low Pt loading<50μg·cm^(-2).
基金National Natural Science Foundation of China(22278084)State Key Laboratory of Heavy Oil Processing(SKLHOP202402003)for financing this research.
文摘To achieve palm oil conversion along with a high yield of long‐chain alkane,a series of NiFe layered double oxide catalysts were prepared and employed in the deoxygenation of palm oil.The layered structure of these catalysts was confirmed by XRD and SEM analyses,and Ni and Fe species existed primarily in the forms of Ni^(2+)and Fe^(3+),respectively.It was found that Ni/Fe molar ratio influenced the H_(2)reducibility and surface properties of NiFe catalysts.Specifically,Ni_(2)Fe‐LDO and Ni_(3)Fe‐LDO exhibited higher reducibility under H_(2)atmosphere.Moreover,the Ni_(2)Fe‐LDO catalyst contained a higher concentration of surface oxygen species(Osurf).Deoxygenation results demonstrated that the Ni_(2)Fe‐LDO catalyst achieved superior palm oil conversion,higher liquid product yield and enhanced selectivity toward C_(15)–C_(18)hydrocarbons compared to other catalysts.This improved performance was attributed to its higher hydrogen dissociation activity and enhanced adsorption capacity for palm oil molecules.Furthermore,reaction condition studies revealed that palm oil was completely converted,yielding 86.8%liquid product with 81.8%selectivity of C_(15)–C_(18)hydrocarbons at 350℃under 7 MPa H_(2)pressure.This finding provides an insight into the development of efficient catalysts for the deoxygenation of fatty compounds to biofuels.
基金financially supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)via a Discovery Grant,and Canadian Urban Transit Research&Innovation Consortium(CUTRIC)via Project No.160028.
文摘Catalyst layer(CL)is the core component of proton exchange membrane(PEM)fuel cells,which determines the performance,durability,and cost.However,difficulties remain for a thorough understanding of the CLs’inhomogeneous structure,and its impact on the physicochemical and electrochemical properties,operating performance,and durability.The inhomogeneous structure of the CLs is formed during the manufacturing process,which is sensitive to the associated materials,composi-tion,fabrication methods,procedures,and conditions.The state-of-the-art visualization and characterization techniques are crucial to examine the CL structure.The structure-dependent physicochemical and electrochemical properties are then thoroughly scrutinized in terms of fundamental concepts,theories,and recent progress in advanced experimental techniques.The relation between the CL structure and the associated effective properties is also examined based on experimental and theoretical findings.Recent studies indicated that the CL inhomogeneous structure also strongly affects the performance and degradation of the whole fuel cell,and thus,the interconnection between the fuel cell performance,failure modes,and CL structure is comprehensively reviewed.An analytical model is established to understand the effect of the CL structure on the effective properties,performance,and durability of the PEM fuel cells.Finally,the challenges and prospects of the CL structure-associated studies are highlighted for the development of high-performing PEM fuel cells.
文摘The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most expensive component due to the use of a Pt catalyst. Apart from the ORR itself, the species transport to and from the reactive sites determines the performance of the PEFC. The effective transport properties of the species in the CCL depend on its nanostructure. Therefore a three-dimensional reconstruction of the CCL is required. A series of two-dimensional images was obtained from focused ion beam- scanning electron microscope （FIB-SEM） imaging and a segmentation method for the two-dimensional images has been developed. The pore size distribution （PSD） was calculated for the three-dimensional geometry. The influence of the alignment and the anisotropic pixel size on the PSD has been investigated. Pores were found in the range between 5 nm and 205 nm. Evaluation of the Knudsen number showed that gas transport in the CCL is governed by the transition flow regime. The liquid water transport can be described within continuum hydrodynamics by including suitable slip flow boundary conditions.
基金financially supported in part by funds from the National Natural Science Foundation of China(Grant No.20606025)the Project of Creative Research Groups from Universities(IRT0641).
文摘A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells(PEMFC)was established by Monte Carlo method.The model takes into account all the four components in a typical PEMFC catalyst layer:platinum(Pt),carbon,ionomer and pore.The elemental voxels in the lattice were setfine enough so that each average sized Pt particulate in Pt/C catalyst can be represented.Catalyst utilization in the modeled catalyst layer was calculated by counting up the number of facets of Pt voxels where“three phase contact”are met.The effects of some factors,including porosity,ionomer content,Pt/C particle size and Pt weight percentage in the Pt/C catalyst,on catalyst utilization were investigated and discussed.
基金This work was financially supported by the National Key Research and Development Program of China(No.2020YFB1506300)the National Natural Science Foundation of China(No.21901019)+1 种基金the Beijing Institute of Technology Research and Innovation Promoting Project(No.2022YCXY024)The authors acknowledge the financial support of Chongqing Natural Science Foundation(No.cstc2020jcyj-msxmX0759).
文摘The effective management of oxygen transport resistance(OTR)within the cathode catalyst layer(CCL)is crucial for achieving a high catalyst performance at low platinum(Pt)loading.Over the past two decades,significant advancements have been made in the development of various high active platinum-based catalysts,aiming at enhancing oxygen mass transport and the oxygen reduction reaction(ORR).However,experimental investigations of transport processes in porous media are often computational costs and restrained by limitations in in-situ measurement capabilities,as well as spatial and temporal resolution.Fortunately,numerical simulation provides a valuable alternative for unveiling the intricate relationship between local transport properties and overall cell performance that remain unresolved or uncoupled through experimental approach.In this review,we elucidate the primary experimental and numerical efforts undertaken to improve OTR.We consolidate the available literature on OTR values and perform a quantitative comparison of the effectiveness of different strategies in mitigating OTR.Furthermore,we analyze the intrinsic limitations and challenges associated with current experimental and numerical methods.Finally,we outline future prospect for advancements in both experimental techniques and modelling methods.
基金support from the National Natural Science Foundation of China(No.22005051)Guangdong Basic and Applied Basic Research Foundation(Nos.2019A1515110237 and 2022A1515012001)+3 种基金Young Creative Talents Project of the Guangdong Provincial Department of Education(No.2019KQNCX166)Innovation Research Project of University in Foshan City(No.2020XCC09).Grateful acknowledgements are extended to the National Natural Science Foundation of China(No.51872047)Key Project Plat Form Programs and Technology Innovation Team Project of Guangdong Provincial Department of Education(Nos.2019KZDXM039,2019GCZX002,and 2020KCXTD011)Guangdong Provincial Key Research and Development Plan(No.2020B090920001)。
文摘A porous ceramic support is designed as a multi-functional independent catalyst layer for solid oxide fuel cells(SOFCs)running on liquid hydrocarbon fuel.The layer consists of a highly porous Ce_(0.9)Ca_(0.1)O_(2−δ)ceramic backbone and active NiMo catalysts,which could be integrated into the conventional Ni metal containing the anode for internal reforming of the hydrocarbon fuel.Compared to conventional catalyst layers sintered on the anodes,this independent catalyst layer could be simply assembled on top of the anode without additional sintering,thereby avoiding the mismatch of the thermal expansion coefficient between the catalyst layer and the anode and improving stability of a single cell.Moreover,a current collector layer could be inserted between the catalyst and the anode to enhance current collection efficiency and electrochemical performance of the single cell.At 750℃,the independent catalyst layer displays high activity towards the catalytic decomposition of methanol,and the single cell could achieve the maximum power density of 400–500 mW·cm^(−2)in dry methanol.Furthermore,by employing the independent catalyst layer,the single cell offers additional in-situ catalyst regeneration capability under the methanol operation mode.Feeding 10 mL·min−1 air into an anode channel for 5 min is found to be effective to burn out carbon species in the catalyst layer,which reduces the degradation rate of the cell voltage by orders of magnitude from 2.6 to 0.024 mV·h−1 during the operation of 360 h in dry methanol.The results demonstrate the significance of the independent catalyst layer design for direct internal reforming methanol fuel cells.
基金the Element Innovation Project,Ministry of Education,Japan,and by KAKENHI(26289300).
文摘PtRu supported on TiO2-embedded carbon nanofibers(PtRu/TECNF),which was recently reported as a highly-active catalyst for methanol oxidation,was applied to a direct methanol fuel cell(DMFC),and the power generation performance was compared to that using the commercial PtRu/C.Before the comparison,the effect of the catalyst loading on the power density of the DMFC was investigated using PtRu(18 wt%)/TECNF.The DMFC power density showed a maximum at about a 1.5 mg cm2 PtRu loading that corresponds to about an 80 mm layer thickness.A catalyst layer thicker than this value reduced the power density probably due to the concentration overvoltage.The PtRu content in the PtRu/TECNF was then increased to 30 wt%or more to reduce the layer thickness and to increase the power density.The DMFC performance was compared to that of different anode catalysts at a 1 mg cm2 PtRu loading.The power density was maximized using the PtRu30 wt%/TECNF,which showed a 173 mW cm2 at 353 K and had 66 mm layer thick,that was 26%higher than that of commercial PtRu/C.The current–voltage curve of the DMFC with the PtRu/TECNF suggested an improved mass transport overvoltage,but a little improvement in the activation one despite using the catalyst with about a 2 times higher activity compared to that of the commercial PtRu/C.This was attributed to the lower Pt utilization of the nanofiber catalyst layer.
