Effect of cobalt precursors on Co3O4 anodic catalyst for a membrane-free direct borohydride fuel cell

The fuel discharging efficiency of direct borohydride fuel cell (DBFC) depends on both the anodic catalyst activity and borohydride hydrolysis. In this paper, Co3O4 anodic catalysts prepared from different cobalt sources used in DBFC have been investigated. It showed that the catalytic performance of Co3O4 was associated with its microstructure that relied on the precursor. The maximum power densities obtained was 40, 62 and 28 mW cm−2 of DBFC with Co3O4 catalyzed anode from CoCl2 (marked DBFC-A), Co(NO3)2 (marked DBFC-B) and Co(CH3COO)2 (marked DBFC-C), respectively. The Co3O4-A has the highest number of electron transfer (n = 7.06) which is close to the theoretical value (n = 8), and DBFC-A showed good voltage stability with specific capacity of 720 mAh.g−1. A rapid voltage attenuation occurred in DBFC-B with the specific capacity of 330 mAh.g−1 because Co3O4 from Co(NO3)2 has the higher catalytic activity for both borohydride oxidation reaction (BOR) and hydrolysis which lead to the lower fuel utilization efficiency.