Improved methanol electrooxidation catalyzed by ordered mesoporous Pt-Ru-Ir alloy nanostructures with trace Ir content

Abstract

Mesoporous nanostructures of Pt alloy with Ru-Ir as trimetallic electrocatalyst exhibits significant performance for direct methanol fuel cell (DMFC). In this study, the ordered mesoporous nanostructure (OMNs) of Pt-Ru-Ir catalyst was prepared through the KIT-6 mesoporous silica template-assisted chemical reduction method. The OMN of Pt-Ru-Ir possesses high Pt utilization and a low Ir content, resulting in promoted MOR kinetics by the bi-functional mechanism of its oxophilic nature. In addition, the oxides of both Ru and Ir further enhanced the electrocatalytic efficiency of Pt by producing more active sites owing to its ordered mesoporous morphology and bifunctional mechanism. Furthermore, the OMNs of Pt0.7Ru0.25Ir0.05 electrocatalyst has a substantial electrochemical surface area (ECSA) of 78.35 m2 g−1 with 1721 mA mg−1 of mass activity, which is comparatively 2-3 times higher than all other catalysts reported here. Notably, the ECSA loss (19.5 %) after 5000 durability cycles was found much lesser than other compositions, Pt/C and Pt0.7Ru0.3 catalyst owing to the synergistic effect between Pt and Ru with a trace amount of Ir, smaller particle size, and unique ordered mesoporous morphology. Another significant factor is the rate of CO poisoning during MOR, which was found to be much lesser than others for the Pt0.7Ru0.25Ir0.05 catalyst (∼0.0047 %) studied by chronoamperometry test. The results indicate that the unique OMNs of Pt-Ru-Ir is an excellent MOR catalyst for DMFC applications.