Zirconium phosphate nanosheets coated asymmetric polybenzimidazole membrane boosting the durability of HT-PEM fuel cells

Abstract

High temperature proton exchange membrane fuel cells (HT-PEMFCs) has become one of the most promising sustainable energy conversion technologies due to its cleanliness, high resistance to CO toxicity and simplified hydrothermal management. A major challenge is how to improve the acid retention in phosphoric acid (PA)-doped polymer electrolytes in HT-PEMFCs to obtain cells with extended durability. In this work, asymmetric PA-doped polybenzimidazole membranes (PA-APBI-ZrP(X)) with PA-doped poly [2,2‘-(p-oxydiphenyl)-5,5’-biphenylimidazole] (OPBI) membranes as the substrate and the OPBI/zirconium phosphate nanosheets composite coating layer (OPBI/ZrP(X)) on the cathode-contact side were prepared for the first time via hot pressure transfer method. The parallel distribution and high barrier property of the ZrP nanosheets constructed tortuous ion transport channels and mitigated the PA loss from membrane to the catalyst layer, which significantly improved the durability of HT-PEMFCs. The prepared PA-APBI-ZrP(20) membranes exhibited a low voltage decay rate in the 72 h accelerated stress test (AST), and the cell voltage achieved almost no decay (4.76 μV h⁻¹) for 420 h at the operating current. The idea of cathode-side coating with a nanocomposite layer provides a feasible strategy to achieve the long-term operation of HT-PEMFCs.