A hybrid cathode catalytic layer composed of M–N–C and Pt/C for direct methanol fuel cells with high methanol tolerance

Abstract

Pt/C based direct methanol fuel cells (DMFCs) always suffer from a serious methanol crossover under a high concentration of methanol solution. In this paper, we report a novel hybrid cathode catalytic layer (CCL) consisting of a physical blend of Pt/C and Fe-N-C. DMFC based on the hybrid CCL with an optimized loadings (0.25 mg cm−2 Fe-N-C and 2 mgPt cm-2Pt/C) outputs a high power density of 28.87 mW cm−2 at 10 M methanol, and the single Pt/C based cell only shows a low power density of 12.04 mW cm−2 in comparison. Such a large improvement attributes to the increasing amount of reactive oxygen species (ROS), which is produced by Fe-N-C via an incomplete four-electron transfer process in oxygen reduction reaction (ORR). Inspired by this strategy, several M−N−C catalysts were synthesized, among which Cu-N-C shows the most brilliant performance to enhance the methanol tolerance of Pt/C. The peak power density of DMFC with Cu-N-C based hybrid CCL exceeds 31 mW cm−2 at 10 M methanol, which is superior to that of cells with Fe-N-C based hybrid CCL. This work provides a new approach for designing DMFCs with high energy density, which is practical for applications of portable power devices.