Durable M-N-C Catalysts for Oxygen Reduction Reaction (ORR) and Hydrogen Peroxide Reduction Reaction (PRR) in Platinum Group Metal-Free Direct Borohydride Fuel Cells

The atomically dispersed transition metal with nitrogen-doped carbon (M-N-C) has been studied as a possible replacement for platinum group metal (PGM) catalysts in fuel cell electrodes. In this work, the Fe-N-C and Co-N-C are used as a hydrogen peroxide reduction reaction (PRR) catalysts in direct borohydride fuel cells (DBFCs). Using half-cell and membrane electrode assembly (MEA) configurations, the PRR activity and durability of M-N-C are assessed. The Fe-N-C has higher activity on PRR than Co-N-C. Co-N-C is more stable than Fe-N-C under DBFC cathode, where hydrogen peroxide and sulfuric acid electrolyte are used as fuel. In the DBFC durability test, Fe-N-C demonstrates a performance loss of 18.6% following an accelerated durability test, whereas Co-N-C shows a more stable performance with a performance loss of only 6.7%. To examine the degradation mechanism of M-N-C, post-mortem XPS and Raman spectroscopy measurements are conducted. In addition, the density functional theory (DFT) simulation supports the Co-N-C stability on the catholyte. The usage of PGM catalysts is all replaced to transition metal catalysts in liquid fuel-operated DBFC systems.