Enhancing the methanol tolerance of ultrasmall platinum nanoparticles and manganese oxide onto carbon for direct methanol fuel cell: The importance of the synthesis procedure

Abstract

Pt-based cathodes in direct methanol fuel cells are promising materials for a wide range of applications. However, such materials suffer significant performance loss due to severe methanol crossover from anode to cathode, resulting in mixed potentials from methanol oxidation and oxygen reduction reaction. Herein, we proposed some facile synthesis procedures to avoid Pt active sites contamination from methanol. The strategy was to associate controlled ultrasmall Pt nanoparticles (NPs), Vulcan XC-72, and MnOx species prepared from Mn(NO3)2.4H2O. Interestingly, we have observed that depending on the synthetic pathway chosen, the methanol-tolerance ability of the material increased, suggesting different interactions among the components of the catalyst. The results indicated an improved selectivity of the system due to a synergy between Pt and MnOx. The best strategy was the immobilization of ultrasmall Pt NPs (~2 nm) on carbon black, before impregnation and thermal decomposition of MnOx, which almost wholly suppressed the methanol oxidation interference on the system. Also, the optimized cathode presented a comparable performance for ORR to the traditional Pt/C without methanol addition. To further rationalize such findings, physical and electrochemical characterizations were successfully performed, which allowed us to better understand the proposed catalysts and their different methanol-tolerance abilities.