Fabrication of Stable and Well‐connected Proton Path in Catalyst Layer for High Temperature Polymer Electrolyte Fuel Cells

Abstract It is of importance to establish stable and well‐connected proton path in the catalyst layer to promote the fuel cell performance. Here, we describe a novel method to fabricate stable and efficient proton path for high temperature polymer electrolyte fuel cells (HT‐PEFCs), in which the ionic liquid is doped into the platinum electrocatalyst. The electrochemical results depict that ionic liquid doped electrocatalyst exhibits comparable electrochemical surface area (ESA) and enhanced durability indicating that ionic liquid negligibly affects the hydrogen adsorption/desorption process and protects the electrocatalyst from carbon corrosion. Interestingly, the catalyzing activity toward oxygen reduction reaction (ORR) of Pt electrocatalyst is boosted after doping with ionic liquid mainly due to the modified electronic structures of Pt atoms induced by nitrogen atoms from ionic liquid resulting in weak interaction between Pt atoms and intermediates. The fuel cell performance of ionic liquid doped electrocatalyst is much improved ascribed to the homogeneously dispersed ionic liquid on the surface of Pt electrocatalyst facilitating the fabrication of triple phase boundaries (TPBs) as a result of efficient proton conduction in the catalyst layer. The fuel cell performance only decreases 10 % after 100,000 potential cycles from 1.0 to 1.5 V versus RHE suggesting that ionic liquid forms a stable proton path in the catalyst layer. Thus, the ionic liquid doped Pt electrocatalyst is applicable for the real HT‐PEFC operation.