Phase-controlled evolution of cobalt active sites assisted by carbon substrate for high-efficiency oxygen reduction reaction

Abstract

Advancement of Co-N-C materials for efficient oxygen reduction reaction (ORR) is essential, given their potential as highly attractive alternatives to Pt-based catalysts. Here, we propose a novel strategy for the controllable evolution of active Co sites via constructing a carbon substrate to fabricate a high-performance Co-N-C catalyst for ORR, which involves initiating a metallic Co phase adjacent to atomic Co sites to modify the electronic structures and promote synergistic effects. The resulting catalyst (C-SDB-Co) demonstrates exceptional ORR activity (E_1/2=0.95 V vs. RHE) and zinc-air battery capability surpassing the benchmark catalysts in alkaline solutions. As evidenced by density functional theory (DFT) calculations, the remarkable ORR performance of C-SDB-Co originates from the synergy between the two Co phases that effectively regulates the electronic structure and lowers the energy barrier of intermediate adsorption. This study provides a new perspective on enhancing the catalytic activity of Co-N-C materials through innovative carbon substrate design and active site regulation.