The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant a...The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.展开更多
Single-atom transition metal-nitrogen-doped carbons(SA M-N-Cs)catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).Howev...Single-atom transition metal-nitrogen-doped carbons(SA M-N-Cs)catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).However,enhancing their performance for practical applications remains a significant challenge.This review summarizes recent advances in enhancing the intrinsic activity of SA M-N-C catalysts through various strategies,such as tuning the coordination environment and local structure of central metal atoms,heteroatom doping,and the creation of dual-/multi metal sites.Additionally,it discusses methods to increase the density of M-Nx active sites,including chelation,defect capture,cascade anchoring,spatial confinement,porous structure design,and secondary doping.Finally,it outlines future directions for developing highly active and stable SA M-N-C catalysts,providing a comprehensive framework for the design of advanced catalysts.展开更多
Fe-N-C catalysts represent the most promising class of platinum group metal-free(PGM-free)catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs),exhibiting intrinsic activity po...Fe-N-C catalysts represent the most promising class of platinum group metal-free(PGM-free)catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs),exhibiting intrinsic activity potentially competitive with commercial Pt/C benchmarks.However,critical challenges persist[1].As revealed by theoretical calculations,the enhancement of intrinsic activity in Fe-N-C catalysts is constrained by inherent scaling relations among the adsorption free energies of ORR intermediates on the catalyst surface.展开更多
The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volu...The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volumetric power density.Our previous study proposed an ultrathin GDL-less PEMFC that uses metal foam to replace traditional flow fields and GDLs,significantly reducing mass transport distance and cell thickness while enhancing volumetric power density.To ensure contact and transition between the catalyst layer and metal foam,an ultrathin carbon nanofiber film(CNFF)is employed in this structure.This study systematically investigates the effect of CNFF thickness on the performance of ultrathin GDL-less PEMFCs.Results demonstrate that the protective effect of CNFF on the catalyst coated membrane(CCM)is strongly correlated with its thickness.Specifically,thinner CNFF offers less protection to the catalyst layer,resulting in an 30%difference in electrochemical active surface area(ECSA).A moderate increase in thickness reduces ohmic overpotential and enhances Knudsen diffusion within the oxygen catalyst layer,while excessive thickness leads to a decrease in oxygen molecular diffusion.Additionally,thicker CNFF provides better water storage and more effective water management under medium current densities,although performance degrades at ultrahigh current densities.Overall,the 25-μm CNFF balances these various factors to achieve the best integrated performance.These findings highlight that the optimal performance of GDL-less PEMFCs can be achieved by regulating the thickness of CNFF.展开更多
Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and effic...Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and efficient energy technologies,are constrained in their performance enhancement by the sluggish oxygen reduction reaction(ORR)kinetics at the cathode,anode CO poisoning(e.g.,from methanol crossover)and intricate water management dilemmas[1].展开更多
Multi-site coupling is a promising strategy for developing highly efficient and CO-resistant hydrogen oxidation reaction(HOR)catalysts for proton exchange membrane fuel cells(PEMFCs).However,designing multifunctional ...Multi-site coupling is a promising strategy for developing highly efficient and CO-resistant hydrogen oxidation reaction(HOR)catalysts for proton exchange membrane fuel cells(PEMFCs).However,designing multifunctional synergistic schemes for single-atom sites remains a significant challenge.Herein,we propose a dual-template-confined oxophilic engineering strategy to construct well-dispersed iridium-nickel(IrNi)atomic dimers adjacent to IrNi nanoclusters on porous nitrogen-doped carbon(IrNi_(Dimer/NC1.8)-PNC).The paired IrNi dimer features an asymmetric Ir-N_(3)configuration coordinated with heteroatomic Ni-N_(3)O via an N-bridge.Remarkably,IrNi_(Dimer/NC1.8)-PNC exhibits a~23-fold enhancement in mass activity(4.36 A mg-1Ir at 20 mV)and 5-fold longer stability compared to benchmarking Pt/C toward HOR,while achieving a high rated power density of 1.18 W cm^(-2)in PEMFC anode applications.Furthermore,IrNi_(Dimer/NC1.8)-PNC demonstrates superior CO tolerance over monometallic Ir and Pt/C in both half-cell and full-cell devices.Combined experimental and density functional theory studies reveal that oxophilic Ni modulates the electronic environment of Ir through alloying and dimer interactions,thereby enhancing HOR activity.Importantly,the asymmetric IrNi dimer enables efficient CO^(*)and OH^(*)co-adsorption while facilitating CO_(2)^(*)desorption,synergistically mitigating CO poisoning and improving atom utilization efficiency.This work provides a design strategy and fundamental insights for multi-site synergistic catalysts in PEMFC anodes.展开更多
To address the issues of insufficient and imbalanced data samples in proton exchange membrane fuel cell(PEMFC)performance degradation prediction,this study proposes a data augmentation-based model to predict PEMFC per...To address the issues of insufficient and imbalanced data samples in proton exchange membrane fuel cell(PEMFC)performance degradation prediction,this study proposes a data augmentation-based model to predict PEMFC performance degradation.Firstly,an improved generative adversarial network(IGAN)with adaptive gradient penalty coefficient is proposed to address the problems of excessively fast gradient descent and insufficient diversity of generated samples.Then,the IGANis used to generate datawith a distribution analogous to real data,therebymitigating the insufficiency and imbalance of original PEMFC samples and providing the predictionmodel with training data rich in feature information.Finally,a convolutional neural network-bidirectional long short-termmemory(CNN-BiLSTM)model is adopted to predict PEMFC performance degradation.Experimental results show that the data generated by the proposed IGAN exhibits higher quality than that generated by the original GAN,and can fully characterize and enrich the original data’s features.Using the augmented data,the prediction accuracy of the CNN-BiLSTM model is significantly improved,rendering it applicable to tasks of predicting PEMFC performance degradation.展开更多
Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructe...Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructed based on Pt-decorated nanoporous gold(NPG-Pt)with sub-Debye-length thickness for proton transfer.In the absence of ionomer incorporation in the CLs,these integrated carbon-free electrodes can deliver maximum mass-specific power density of 198.21 and 25.91 kW·gPt^(-1) when serving individually as the anode and cathode,at a Pt loading of 5.6 and 22.0 pg·cm^(-2),respectively,comparable to the best reported nano-catalysts for PEMFCs.In-depth quantitative experimental measurements and finite-element analyses indicate that improved proton conduction plays a critical role in activation,ohmic and mass transfer polarizations.展开更多
Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,red...Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.展开更多
The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters a...The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters and surface properties of the bipolar plate flow channels on the PEMFC performance is thoroughly examined on a commercial scale PEMFC with an active area of 203.49 cm2.The fabrication of bipolar plate flow channels with different structural and wetting properties is achieved using a novel ultrafast laser technique and a conventional milling method.Single cell stack is assembled and subjected to polarization curve tests.The findings indicate that decreasing the width of the flow channels generally improves the performance of commercial-scale PEMFCs.The minimum allowable channel width is dependent on the length of the flow channels.Interestingly,flow channels with higher hydrophilicity and surface adhesion do not necessarily lead to poorer water removal capability,which may be attributed to the formation of a thin water film on superhydrophilic channel surfaces.This research provides valuable insights into the design of optimal flow fields for commercial-scale PEMFCs.展开更多
基金financially supported by the Fundamental Re-search Funds for the Central Universities(No.2023CDJXY-016)the Outstanding Youth Project of Natural Science Foundation of Guangdong Province(Grant No.2022B1515020020).
文摘The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.
基金supported by the National Natural Science Foundation of China(Grant No.22379123)the High-level Innovation and Entrepreneurship Talent Project from Qinchuangyuan of Shaanxi Province(Grant No.QCYRCXM-2022-226)+1 种基金the Key Research and Development Program of Shaanxi Province(Grant No.2024CY-GJHX-25)the National Natural Science Foundation of China,Pilot Group Program of the Research Fund for International Senior Scientists(Grant No.22250710676).
文摘Single-atom transition metal-nitrogen-doped carbons(SA M-N-Cs)catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).However,enhancing their performance for practical applications remains a significant challenge.This review summarizes recent advances in enhancing the intrinsic activity of SA M-N-C catalysts through various strategies,such as tuning the coordination environment and local structure of central metal atoms,heteroatom doping,and the creation of dual-/multi metal sites.Additionally,it discusses methods to increase the density of M-Nx active sites,including chelation,defect capture,cascade anchoring,spatial confinement,porous structure design,and secondary doping.Finally,it outlines future directions for developing highly active and stable SA M-N-C catalysts,providing a comprehensive framework for the design of advanced catalysts.
文摘Fe-N-C catalysts represent the most promising class of platinum group metal-free(PGM-free)catalysts for the oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs),exhibiting intrinsic activity potentially competitive with commercial Pt/C benchmarks.However,critical challenges persist[1].As revealed by theoretical calculations,the enhancement of intrinsic activity in Fe-N-C catalysts is constrained by inherent scaling relations among the adsorption free energies of ORR intermediates on the catalyst surface.
基金support from the National Natural Science Foundation of China for Distinguished Young Scholars(52225604)the Jilin Province Science and Technology Development Program(grant No.20230301017ZD)the Marine Defense Innovation Fund of China Ship Development and Design Center(Grant No.2023712-01).
文摘The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volumetric power density.Our previous study proposed an ultrathin GDL-less PEMFC that uses metal foam to replace traditional flow fields and GDLs,significantly reducing mass transport distance and cell thickness while enhancing volumetric power density.To ensure contact and transition between the catalyst layer and metal foam,an ultrathin carbon nanofiber film(CNFF)is employed in this structure.This study systematically investigates the effect of CNFF thickness on the performance of ultrathin GDL-less PEMFCs.Results demonstrate that the protective effect of CNFF on the catalyst coated membrane(CCM)is strongly correlated with its thickness.Specifically,thinner CNFF offers less protection to the catalyst layer,resulting in an 30%difference in electrochemical active surface area(ECSA).A moderate increase in thickness reduces ohmic overpotential and enhances Knudsen diffusion within the oxygen catalyst layer,while excessive thickness leads to a decrease in oxygen molecular diffusion.Additionally,thicker CNFF provides better water storage and more effective water management under medium current densities,although performance degrades at ultrahigh current densities.Overall,the 25-μm CNFF balances these various factors to achieve the best integrated performance.These findings highlight that the optimal performance of GDL-less PEMFCs can be achieved by regulating the thickness of CNFF.
文摘Covalent organic framework ionomers enable synergistic efficient transport of protons and oxygen in medium-temperature proton exchange membrane fuel cells Proton exchange membrane fuel cells(PEMFCs),as clean and efficient energy technologies,are constrained in their performance enhancement by the sluggish oxygen reduction reaction(ORR)kinetics at the cathode,anode CO poisoning(e.g.,from methanol crossover)and intricate water management dilemmas[1].
基金supported by the National Natural Science Foundation of China(22279079 and 22472101)Guangdong Science and Technology Department Program(2021QN02L252,2023A1515010021,and 2024A1515011543)Research Team Cultivation Program of Shenzhen University(2023QNT007)。
文摘Multi-site coupling is a promising strategy for developing highly efficient and CO-resistant hydrogen oxidation reaction(HOR)catalysts for proton exchange membrane fuel cells(PEMFCs).However,designing multifunctional synergistic schemes for single-atom sites remains a significant challenge.Herein,we propose a dual-template-confined oxophilic engineering strategy to construct well-dispersed iridium-nickel(IrNi)atomic dimers adjacent to IrNi nanoclusters on porous nitrogen-doped carbon(IrNi_(Dimer/NC1.8)-PNC).The paired IrNi dimer features an asymmetric Ir-N_(3)configuration coordinated with heteroatomic Ni-N_(3)O via an N-bridge.Remarkably,IrNi_(Dimer/NC1.8)-PNC exhibits a~23-fold enhancement in mass activity(4.36 A mg-1Ir at 20 mV)and 5-fold longer stability compared to benchmarking Pt/C toward HOR,while achieving a high rated power density of 1.18 W cm^(-2)in PEMFC anode applications.Furthermore,IrNi_(Dimer/NC1.8)-PNC demonstrates superior CO tolerance over monometallic Ir and Pt/C in both half-cell and full-cell devices.Combined experimental and density functional theory studies reveal that oxophilic Ni modulates the electronic environment of Ir through alloying and dimer interactions,thereby enhancing HOR activity.Importantly,the asymmetric IrNi dimer enables efficient CO^(*)and OH^(*)co-adsorption while facilitating CO_(2)^(*)desorption,synergistically mitigating CO poisoning and improving atom utilization efficiency.This work provides a design strategy and fundamental insights for multi-site synergistic catalysts in PEMFC anodes.
基金supported by the Jiangsu Engineering Research Center of the Key Technology for Intelligent Manufacturing Equipment and the Suqian Key Laboratory of Intelligent Manufacturing(Grant No.M202108).
文摘To address the issues of insufficient and imbalanced data samples in proton exchange membrane fuel cell(PEMFC)performance degradation prediction,this study proposes a data augmentation-based model to predict PEMFC performance degradation.Firstly,an improved generative adversarial network(IGAN)with adaptive gradient penalty coefficient is proposed to address the problems of excessively fast gradient descent and insufficient diversity of generated samples.Then,the IGANis used to generate datawith a distribution analogous to real data,therebymitigating the insufficiency and imbalance of original PEMFC samples and providing the predictionmodel with training data rich in feature information.Finally,a convolutional neural network-bidirectional long short-termmemory(CNN-BiLSTM)model is adopted to predict PEMFC performance degradation.Experimental results show that the data generated by the proposed IGAN exhibits higher quality than that generated by the original GAN,and can fully characterize and enrich the original data’s features.Using the augmented data,the prediction accuracy of the CNN-BiLSTM model is significantly improved,rendering it applicable to tasks of predicting PEMFC performance degradation.
基金financially supported by the National Natural Science Foundation of China(52073214,21603161,51671145,51761165012 and U1804255)the National Science Fund for Distinguished Young Scholars(No.51825102)the Tianjin Municipal Major Project of New Materials(No.16ZXCLGX00120).
文摘Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructed based on Pt-decorated nanoporous gold(NPG-Pt)with sub-Debye-length thickness for proton transfer.In the absence of ionomer incorporation in the CLs,these integrated carbon-free electrodes can deliver maximum mass-specific power density of 198.21 and 25.91 kW·gPt^(-1) when serving individually as the anode and cathode,at a Pt loading of 5.6 and 22.0 pg·cm^(-2),respectively,comparable to the best reported nano-catalysts for PEMFCs.In-depth quantitative experimental measurements and finite-element analyses indicate that improved proton conduction plays a critical role in activation,ohmic and mass transfer polarizations.
基金the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No.754354.
文摘Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.
基金National Natural Science Foundation of China(No.52022050 and 52002210)Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)2021 Independent research project of SVM.
文摘The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters and surface properties of the bipolar plate flow channels on the PEMFC performance is thoroughly examined on a commercial scale PEMFC with an active area of 203.49 cm2.The fabrication of bipolar plate flow channels with different structural and wetting properties is achieved using a novel ultrafast laser technique and a conventional milling method.Single cell stack is assembled and subjected to polarization curve tests.The findings indicate that decreasing the width of the flow channels generally improves the performance of commercial-scale PEMFCs.The minimum allowable channel width is dependent on the length of the flow channels.Interestingly,flow channels with higher hydrophilicity and surface adhesion do not necessarily lead to poorer water removal capability,which may be attributed to the formation of a thin water film on superhydrophilic channel surfaces.This research provides valuable insights into the design of optimal flow fields for commercial-scale PEMFCs.
