Application of rock-salt-type Co–Mn oxides for alkaline polymer electrolyte fuel cells

Co–Mn oxides are a group of highly effective non-precious metal oxygen reduction reaction (ORR) catalysts for alkaline polymer electrolyte fuel cells (APEFCs). Despite being widely studied in alkaline solutions, limited studies of them have been developed in APEFCs. In this work, we evaluate the performance of a rock-salt-type Co–Mn composite oxides (CoMnO2/C) in both alkaline solution and APEFCs. Other than that, we also test its durability in APEFCs and investigate its degradation mechanism. CoMnO2/C exhibits a high ORR activity in both rotate disk electrode (RDE) study and APEFCs test. The ORR half-wave potential is 0.86 V in 1 M KOH, and the peak power density (PPD) reaches 1.2 W/cm2 in H2–O2 APEFCs when using PtRu as anode. In air (CO2-free) condition, APEFC reaches a PPD of 0.83 W/cm2, and can operate over 40 h at a constant current density of 200 mA/cm2. Further experiments reveal that the cell performance degradation can be ascribed to the dissolution and valence increase of Mn from +3 to +3.6 on the catalysts surface.