Significantly improved stability and water retention for Pt supported on W-doped SnO2 to catalyse the oxygen reduction reaction in proton exchange membrane fuel cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) have been commercialized, but their elevated costs and inadequate catalytic efficiencies for the oxygen reduction reaction (ORR) have hindered broader use. Metal oxides demonstrate high stability and water retention, as well as strong interactions with metal nanoparticles. However, their conductivities and surface areas are lower than those of carbon. This study introduces a novel Pt–oxide–carbon composite ORR catalyst. The Pt nanoparticles were anchored to a W_0.02–SnO₂–C substrate and demonstrated significantly higher stability and catalytic activity. The composite electrocatalyst exhibited a mass activity (MA) of 0.23 A mg_pt⁻¹ at 0.9 V (vs. RHE). The use of Pt/W_0.02–SnO₂–C as the cathode in a fuel-cell assessment (under H₂–air conditions at 80 °C) resulted in a peak power density of 1.04 W cm², and 89.2% of the initial value was retained after 50 000 cycles over the potential range 0.60–0.95 V. Due to the electronic metal–support interaction (EMSI) between Pt and W_0.02–SnO₂–C, electron transfer from Pt to the support was accelerated. This diminished the surface electron density of Pt and inhibited the dissolution of Pt nanoparticles. Thermogravimetric (TG) analyses were also conducted to examine the water losses from the W–SnO₂–C and pure XC-72R carbon black samples at high temperatures. The water weight in W_0.02–SnO₂–C decreased by 15.3%, which was lower than the 18.8% decrease from XC-72R. Additionally, in the membrane electrode assemblies (MEAs) tested at 100% RH and 60% RH, the peak power density of the fuel cell with Pt/W_0.02–SnO₂–C was decreased by 13.7% at 60%, in contrast to the 25.1% reduction observed for JM Pt/C. These findings highlight the superior water retention of W_0.02–SnO₂–C, which expedited proton transfer in the catalytic layer. This improvement enhanced the catalytic performance, offering significant advantages for practical PEMFCs.