Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is t...Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.展开更多
The ordered membrane electrode assembly(MEA)has gained much attention because of its potential in improving mass transfer.Here,a comprehensive study was conducted on the influence of the patterned microporous layer(MP...The ordered membrane electrode assembly(MEA)has gained much attention because of its potential in improving mass transfer.Here,a comprehensive study was conducted on the influence of the patterned microporous layer(MPL)on the proton exchange membrane fuel cell performances.When patterned MPL is employed,grooves are generated between the catalyst layer and the gas diffusion layer.It is found that the grooves do not increase the contact resistance,and it is beneficial for water retention.When the MEA works under low humidity scenarios,the MEA with patterned MPL illustrated higher performance,due to the reduced inner resistance caused by improved water retention,leading to increased ionic conductivity.However,when the humidity is higher than 80%or working under high current density,the generated water accumulated in the grooves and hindered the oxygen mass transport,leading to a reduced MEA performance.展开更多
Surface modification is a direct and effective way to enhance the efficiency of heat exchangers. Surface modification by forming a microporous coated layer can greatly enhance the boiling heat transfer and thus achiev...Surface modification is a direct and effective way to enhance the efficiency of heat exchangers. Surface modification by forming a microporous coated layer can greatly enhance the boiling heat transfer and thus achieve a high performance. In this paper, we systematically investigate the boiling behavior on a plain surface with/ without sintered microporous coatings of copper powder. The results demonstrated that the sintered surface has a better performance in nucleate boiling due to the increased nucleation sites. The superheat degree is lower and the bubble departure diameter is larger for the sintered surface than for the plain surface, so the heat can be carried away more efficiently on the sintered surface. In addition, the heat transfer capacity on the sintered surface depends on both the powder size and the coating thickness for a high flux tube. The optimum heat transfer capacity can be obtained when the thickness of the microporous coating layer is 3-5 times of the sintered powder diameter. As a result, the heat transfer coefficient tube can be up to 3 times higher for the tube with a sintered surface than that with a plain surface, showing a pronounced enhancement in heat transfer and a high potential in chemical engineering industry application.展开更多
基金supported by China National Postdoctoral Program for Innovative Talents (BX20230121)China Postdoctoral Science Foundation (2023M741163)Shanghai Super Postdoctoral Incentive Program (2023741)。
文摘Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.
基金supported by Beijing Natural Science Foundation(No.Z210016).
文摘The ordered membrane electrode assembly(MEA)has gained much attention because of its potential in improving mass transfer.Here,a comprehensive study was conducted on the influence of the patterned microporous layer(MPL)on the proton exchange membrane fuel cell performances.When patterned MPL is employed,grooves are generated between the catalyst layer and the gas diffusion layer.It is found that the grooves do not increase the contact resistance,and it is beneficial for water retention.When the MEA works under low humidity scenarios,the MEA with patterned MPL illustrated higher performance,due to the reduced inner resistance caused by improved water retention,leading to increased ionic conductivity.However,when the humidity is higher than 80%or working under high current density,the generated water accumulated in the grooves and hindered the oxygen mass transport,leading to a reduced MEA performance.
文摘Surface modification is a direct and effective way to enhance the efficiency of heat exchangers. Surface modification by forming a microporous coated layer can greatly enhance the boiling heat transfer and thus achieve a high performance. In this paper, we systematically investigate the boiling behavior on a plain surface with/ without sintered microporous coatings of copper powder. The results demonstrated that the sintered surface has a better performance in nucleate boiling due to the increased nucleation sites. The superheat degree is lower and the bubble departure diameter is larger for the sintered surface than for the plain surface, so the heat can be carried away more efficiently on the sintered surface. In addition, the heat transfer capacity on the sintered surface depends on both the powder size and the coating thickness for a high flux tube. The optimum heat transfer capacity can be obtained when the thickness of the microporous coating layer is 3-5 times of the sintered powder diameter. As a result, the heat transfer coefficient tube can be up to 3 times higher for the tube with a sintered surface than that with a plain surface, showing a pronounced enhancement in heat transfer and a high potential in chemical engineering industry application.