Engineering mesoporosity promoting high-performance polymer electrolyte fuel cells

Abstract

Proton exchange membranes (PEMs) are a vital component in fuel cells (FCs) that attract significant research interest for the present hydrogen energy use. High proton conductivity of PEMs under various operation conditions highly influences the integrated performance of FCs that determines their commercial applications. Hence mesoporous superacidic sulfated zirconia (S-ZrO2) is fabricated and introduced into Nafion matrix to construct hybrid PEMs. The mesoporosity of S-ZrO2 is demonstrated highly controllable. High mesoporosity leads to increased amount of sulfonic groups (SO3H) aggregating on S-ZrO2 surface. When introduced in PEMs, the highly mesoporous S-ZrO2 chemically enhances the amount of proton-containing groups, structurally improves the density of ion channels, and reserves water as effective reservoirs, which resultantly maintains high proton conductivity under variable conditions, and thus the performance of assembled FCs. The S-ZrO2 exhibits the highest surface area of 181 m2 g−1. The hybrid PEMs loaded with 10 wt% such S-ZrO2 achieve a highest proton conductivity of 0.83 S cm−1 that is ∼7 time of that for pristine Nafion® membranes. The power density at 0.6 V of FCs with the hybrid PEMs is 786 mW cm−2, much higher than that for commercial Nafion 211.