Conductive RuO2 binders enhance mechanical stability of macroporous Nb–SnO2 particles as cathode catalyst supports for high-performance PEFCs†

Abstract

Niobium-doped tin oxide (NTO) particles with a macroporous structure have been developed as catalyst supports for enhancing the durability and performance of polymer electrolyte fuel cells (PEFCs). This macroporous architecture improves the mass transport properties of the electrode. However, their weak mechanical strength can cause structural collapse, thereby limiting single-cell performance at high current densities. In this study, we employed ruthenium oxide (RuO₂) as a binder to integrate with macroporous NTO particles (denoted as NTO/RuO₂). This approach simultaneously enhanced the electrical conductivity and mechanical strength of the catalyst supports, improving the performance of PEFCs. Incorporating RuO₂ binders effectively stabilized the macroporous structure, and the NTO/RuO₂ particles with 50 wt% RuO₂ loading maintained their structural integrity under high compression pressures of up to 40 MPa. The aggregated NTO/RuO₂ particles containing 50 wt% RuO₂ binder also exhibited higher conductivity than the NTO aggregates without RuO₂ binder, which was attributed to the conductive network formed by RuO₂. Importantly, the membrane electrode assembly (MEA) fabricated with macroporous NTO/RuO₂ particles containing 20 wt% RuO₂ binder achieved a maximum current density of 2.16 A cm⁻² at 60 °C and 100% relative humidity (RH), outperforming the MEA utilizing Carbon Vulcan as the support (2.06 A cm⁻²). Furthermore, the enhanced hydrophilic properties of the RuO₂ binder improved water retention at the catalyst layer/membrane interface, thus promoting membrane hydration and overall cell performance at a high temperature of 80 °C and a low RH of 30%.