Two birds with one stone: valence and substrate microenvironment engineering of Co-based catalysts for high-performance borohydride oxidation reaction

Abstract

Direct borohydride fuel cells (DBFCs) urgently need a deep understanding of the electronic structure–activity relationship of the transition metal-based electrode-catalyzed borohydride oxidation reaction (BOR) and an effective strategy to mitigate bubble effect. In this work, phosphorus (P) and oxygen (O) heteroatoms are utilized to regulate the low-valent Co content with high activity towards BOR in the catalytic center, while concurrently modifying the electronic structure of C to construct a microenvironment with strong adsorption for Hatom. The interfacial synergistic effects between the catalytic center and the microenvironment optimize the Hatom reaction pathway to mitigate the bubble effect and enhance fuel utilization. As a result, a record-high peak power density of 806 mW cm−2 is achieved with a CoP/O-C anode in the DBFCs. Macro high-speed camera reveals that the bubble density on the electrode surface is effectively mitigated. This work provides insight and feasible engineering strategies for studying valence-activity and microenvironment-selectivity relationships.