高温质子交换膜燃料电池中阴极双催化层孔结构的设计研究

Design and Study on Pore Structure of Cathode Double Catalytic Layer in High-temperature Proton Exchange Membrane Fuel Cell

优化气体扩散电极(GDE)的结构是提升高温质子交换膜燃料电池(HT-PEMFC)性能、降低成本的重要手段.本工作通过调控内外催化层中碳酸氢铵造孔剂含量,构筑了一种梯度孔分布的双催化层阴极,优化磷酸分布,降低氧传输阻力,从而达到电化学性能提升的目的.结果显示,当内催化层使用46.7%(w) PtCo/C且不添加造孔剂,外催化层使用40%(w) Pt/C且铂与造孔剂质量比为0.53时构成的膜电极,在160℃与常压氢空进料下,其组成的单电池最大功率密度达439 mW·cm^(-2),比未添加造孔剂的单电池最大功率密度高69 mW·cm^(-2).

High-temperature proton exchange membrane fuel cell(HT-PEMFCs)has the advantages of simple hydro-thermal management,strong resistance to CO,direct feeding of reforming gas and high efficiency of cogeneration.It is one of the ideal power sources for the development of clean energy.As the core component of HT-PEMFCs,membrane electrode assembly(MEA)is mainly composed of cathode and anode gas diffusion electrode and proton exchange membrane,which determines the performance and cost of HT-PEMFCs.Therefore,optimizing the structure of gas diffusion electrode(GDE)is an important means to improve the performance and reduce the cost of HT-PEMFC.In this work,from the point of view of catalytic layer,pore-forming agent was introduced into catalytic layer to construct double catalytic layer with different pore structure.Among them,MEA 2 uses 46.7%(w)PtCo/C in the inner catalyst layer without adding pore-forming agent,and the outer catalyst layer uses 40%(w)Pt/C and adds 20%(w)pore-forming agent.It has relatively small ohmic polarization,minimum mass transfer polarization and activation polarization,and has the largest electrochemical active area,and the electrochemical performance is the best.At 160℃and atmospheric pressure,hydrogen and air as fuel,the maximum power density of the single cell composed of the membrane electrode is 439 mW•cm^(−2),which is 69 mW•cm^(−2) higher than that of the single cell without pore-forming agent.Whether the pore-forming agent is added into the inner catalytic layer(CL)or the outer CL,the pore structure is adjusted to optimize the phosphoric acid(PA)distribution and reduce the oxygen mass transfer resistance to improve the electrochemical performance.The former catalyst layer has a greater hydrophobicity change and the electrochemical performance is more affected by the PA content,while the latter catalyst layer hydrophobicity changes less and the electrochemical performance is more affected by the oxygen mass transfer resistance.Excessive addition of pore-forming agent inside or outside CL will produce larger ohmic polarization resistance(R_(Ω)),and the acid drowning caused by insufficient hydrophobicity of CL will further reduce the electrochemical performance of the battery.