It is crucial to develop efficient and inexpensive borohydride oxidation reduction (BOR) electrocatalysts for the practical application of direct borohydride fuel cells (DBFCs). However, until now, there is still rare electrocatalyst that can simultaneously achieve a high BOR rate, high faradaic efficiency, and low BOR onset potential. In this work, we reported an efficient multisite catalyst CoFe&AuC, with a peak power density of 580 mW/cm2 in DBFC (Air as oxidant), which is 2.8 and 4.3 times higher than CoFe&C (210 mW/cm2) and AuC (136 mW/cm2), respectively. Meanwhile, CoFe&AuC also shows a peak power density of 1371 mW/cm2 in DBFC with O2 used as an oxidant. Notably, CoFe&AuC exhibits a high electron transfer number (5.4) and fuel efficiency (65.6 %), suggesting the high selectivity for BOR. In situ spectroscopy combined with density functional theory (DFT) calculations indicate that the enhanced BOR activity can be attributed to the tandem effect between different components: the rapid adsorption and initial oxidation of BH4- to BH3 species on CoFe LDH and the further oxidation of BH3 species on Au nanoparticles, which efficiently break the bottleneck of Au catalyzing BH4-. This work provides a novel pathway for designing multisite electrocatalysts with high BOR activity and selectivity.
Keywords: Borohydride oxidation reaction; CoFe&AuC; DBFC; Fuel utilization; Multisite catalyst.
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