Carbon-coated, methanol-tolerant platinum/graphene catalysts for oxygen reduction reaction with excellent long-term performance

Abstract

The poor stability and methanol tolerance of commercial platinum/carbon (Pt/C) catalysts largely restrict their practical applications for oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). In this report, we designed and prepared Pt/graphene catalysts with a carbon coating of ∼2 nm (C-Glu-G/Pt) by hydrothermal reaction and subsequent carbonization at 700 °C. The carbon coating was found to be effective in protecting susceptible Pt nanoparticles (NPs) from direct exposure to the corrosive environment and minimizing the negative effect of methanol crossover. The resulting C-Glu-G/Pt catalyst exhibited a catalytic activity comparable to that of the Pt/C catalyst, which was further improved by >7 times during cycling tests in the presence of O₂ and reached the highest value at the 8000^th cycle. Such improvement in cycling performance is believed to arise from the corrosion of the carbon coating and the exposure of active sites on Pt NPs. Although the addition of methanol reduced the ORR activity to some extent, C-Glu-G/Pt also showed similar performance improvements in long-term cycling tests. Additionally, it was found that the morphology of C-Glu-G/Pt remained nearly constant after 10 000 cycling tests in methanol-containing electrolyte, reflecting the validity of carbon coating to maintain the number of activated sites and good methanol tolerance.