Controlling fuel crossover and hydration in ultra-thin proton exchange membrane-based fuel cells using Pt-nanosheet catalysts

Abstract

An ultra-thin proton exchange membrane with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on H₂ and O₂. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated, layered double hydroxide (LDH) nanosheets by chemical vapor deposition. After embedding Pt-LDH nanocatalysts in 9 μm-thick Nafion membranes, exfoliated LDH nanosheets effectively captured crossovered H₂ and O₂ through the membranes. Meanwhile, Pt nanocatalysts on LDH nanosheets catalyzed reactions between captured H₂ and O₂ and provided in situ hydration inside Nafion membranes to maintain their proton conductivity level. Furthermore, LDH nanosheets reinforced the Nafion membranes, with 181% improvement in tensile modulus and 166% improvement in yield strength. In a hydrogen fuel cell running with dry fuel, the membrane-electrode assembly employing the Pt-LDH/Nafion membrane showed an improvement of 200% in maximum power density, an increase of 197% in current density at 0.3 V and an improvement of 497% in current density at 0.5 V as compared to those with Nafion 211. The Pt-LDH/Nafion membrane with a thickness of 9 μm exhibited a combination of desirable properties for the development of affordable and durable hydrogen fuel cell technology, including better mechanical properties, higher open-circuit voltage, lower ohmic resistance and enhanced water management in a hydrogen fuel cell without external humidification.