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
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
To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constru...To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon.But the high loading may induce unwanted par-ticle aggregation.In this work,H-PtNi/C with 33%(mass)Pt loading on carbon and monodisperse distri-bution of 3.55 nm PtNi nanoparticles,was prepared by a bimodal-pore route.In electrocatalytic oxygen reduction reaction(ORR),H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C(13.3%(mass))in the half-cell.While in H_(2)-0_(2) MEA,H-PtNi/C delivers the peak power density of 1.51 W·cm^(-2) and the mass transfer limiting current density of 4.4 A·cm^(-2),being 21%and 16%higher than those of L-PtNi/C(1.25 W·cm^(-2),3.8 A·cm^(-2))respectively,which can be ascribed to enhanced mass trans-fer brought by the thinner catalyst layer in the former.In addition,the same method can be used to pre-pare PtFe alloy catalyst with a high-Pt loading of 36%(mass).This work may lead to a range of catalyst materials for the large current density applications,such as fuel cell vehicles.展开更多
Three-dimensionally（3D） ordered mesoporous carbon sphere arrays（OMCS） are explored to support high loading（60 wt%） Pt nanoparticles as electrocatalysts for the methanol oxidation reaction（MOR）.The OMCS has a u...Three-dimensionally（3D） ordered mesoporous carbon sphere arrays（OMCS） are explored to support high loading（60 wt%） Pt nanoparticles as electrocatalysts for the methanol oxidation reaction（MOR）.The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of- 2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area（ECSA）（73.5 m^2g^-1） and electrocatalytic activity（0.69 mA cm^-2）for the MOR compared with the commercial 60 wt% Pt/C catalyst.展开更多
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financially supported by the National Key Research and Development Program of China (2019YFB1504503)the National Natural Science Foundation of China (21878030 and 21761162015)
文摘To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon.But the high loading may induce unwanted par-ticle aggregation.In this work,H-PtNi/C with 33%(mass)Pt loading on carbon and monodisperse distri-bution of 3.55 nm PtNi nanoparticles,was prepared by a bimodal-pore route.In electrocatalytic oxygen reduction reaction(ORR),H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C(13.3%(mass))in the half-cell.While in H_(2)-0_(2) MEA,H-PtNi/C delivers the peak power density of 1.51 W·cm^(-2) and the mass transfer limiting current density of 4.4 A·cm^(-2),being 21%and 16%higher than those of L-PtNi/C(1.25 W·cm^(-2),3.8 A·cm^(-2))respectively,which can be ascribed to enhanced mass trans-fer brought by the thinner catalyst layer in the former.In addition,the same method can be used to pre-pare PtFe alloy catalyst with a high-Pt loading of 36%(mass).This work may lead to a range of catalyst materials for the large current density applications,such as fuel cell vehicles.
基金financial support from the National Natural Science Foundation of China (No. 51172014)the National 973 Program of China (No. 2009CB219903)the Scientific Innovation Grant for Excellent Young Scientists of Hebei University of Technology (No. 2015001)
文摘Three-dimensionally（3D） ordered mesoporous carbon sphere arrays（OMCS） are explored to support high loading（60 wt%） Pt nanoparticles as electrocatalysts for the methanol oxidation reaction（MOR）.The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of- 2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area（ECSA）（73.5 m^2g^-1） and electrocatalytic activity（0.69 mA cm^-2）for the MOR compared with the commercial 60 wt% Pt/C catalyst.
