Study On Stability Enhancement Of HT-PEMFC Based On Catalyst Layer Doping And Support Modification

Compared with traditional PEMFC,high-temperature polymer electrolyte membrane fuel cell（HT-PEMFC）which is based phosphoric acid（PA）-doped polybenzimidazole（PBI）membrane,is the trend of PEMFC development in the future due to its good environmental tolerance,simple water/heat management and quick reaction kinetics.However,it can influence the performance and durability of HT-PEMFC that PA leakage from MEAs,and the catalyst and its supporting accelerated aging.It becomes the significant factors of commercial development of HT-PEMFC.In this article,focusing on components of MEA and the catalyst designing,we put forward strategies that doping in MEA and enhancing catalyst supporting tolerances corrosion,which effectively heightens performance and durability of HT-PEMFC.Firstly,COF materials are incorporated into CL of MEA,to reduce leakage of PA electrolyte and promote the durability of HT-PEMFC.The accelerated durability test（ADT）results show that:the PA loss decreases remarkably.The accumulative PA loss of conventional MEA is up to 13.02 mg in 100 h test.However,this value is reduced by an order of magnitude for the MEA containing COF in the CL,about 4.03 mg.The durability of MEA during 100 h ADT,its degradation rate calculated by linear fitting is about 0.304 m A cm^-2 h^-1,which is significantly lower than that(1.01 m A cm^-2 h^-1)for pristine MEA（0 wt.%COF）.What’s more,due to add COF into CL,the ECSA of Pt is also notable elevated.So,it is envisaged that this COF network possesses the PA retention and proton transfer abilities simultaneously,as well as the good compatibility with the polymer membrane,which could then effectively enhance the performance and durability of HT-PEMFC.Secondly,the SAPO-44 molecular sieve,which contains abundant function groups and porous structure,is added into CL,to possess the PA retention and elevate durability of HT-PEMFC.The SAPO-44 is synthetised by hydrothermal method,and applied it to CL of HT-PEMFC.The ADT results show:owing to incorporate SAPO-44 into CL of MEA,the PA electrolyte leakage is remarkably reduced and the durability of HT-PEMFC is significantly elevated.During 100 h of ADT test,the accumulative PA electrolyte leakage of MEA containing10 wt.%SAPO-44 and the degradation rate of current density is only 0.23 mg and 0.194 m A cm^-2 h^-1,respectively.It is effectively to reduce PA loss and elevate durability of HT-PEMFC,compared with conventional MEA(the PA loss about 0.7 mg and the degradation rate of current density about 2.12 m A cm^-2 h^-1).It is an effective method that adding SAPO-44 molecular sieve into CL to maintain PA electrolyte and heighten the durability of HT-PEMFC.Finally,we concentrate on ameliorating the Pt-based supporting materials.The carbon supporting materials is replaced by C₃N₄ nanorod,to relieve the carbon supporting corrosion and enhance durability of catalyst.The results show:the durability and stability of catalyst is elevated by using C₃N₄nanorod as supporting.In the 2 mol L^-1H₃PO₄,the CV and LSV are tested.During the ADT,the ECSA of Pt/C₃N₄-C is 45.54 m² g_Pt^-1 to 43.48 m² g_Pt^-1,the degradation rate merely 4.5%.Compared with commercial Pt/C,its value is 53.23 m² g _Pt^-1 to36.81 m² g_Pt^-1,the degradation rate up to 30.8%.For ORR test,during ADT,the E_1/2 of commercial Pt/CPt/C₃N₄-C is reduced from 0.75 V to 0.72 V,degradation about 300 m V.However,the E_1/2 of Pt/C₃N₄-C is reduced from 0.78 V to 0.76 V,degradation about 200 m V.So,its durability is considerably elevated by using C₃N₄ nanorod as Pt-based catalyst supporting.