MOF-Derived Zinc Cobalt Sulfides on N, S Co-Doped Carbon as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction

초록

Nowadays, increasing energy demands have triggered intense research for inexpensive, renewable, and harmless energy conversion and storage systems such as fuel cells and rechargeable metal-air batteries. In these applications, the oxygen reduction reaction (ORR) is a key process and rate-determining step because of its four-electron involved process. Pt or its alloys are well known as the state-of-the-art ORR catalysts. However, high cost, scarcity, and poor stability of these Pt-based catalysts have hindered practical application to industrial fields. Therefore, huge efforts have been devoted to developing non-precious metal electrocatalysts with high activity and enhanced stability as promising alternatives to Pt-based catalysts. Herein, we successfully synthesized zinc cobalt sulfides on N, S co-doped porous carbon (Zn-Co-S@NSC) by one-step sulfurization and carbonization of bi-metallic Zn-Co-ZIF. The as-synthesized catalyst maintained the inherent dodecahedral particle shape of ZIF after thermal treatment and exhibited outstanding ORR onset-potential (0.96 V vs. RHE) and half-wave potential (0.83 V vs. RHE), outperforming commercial Pt/C catalyst in alkaline electrolyte. These extraordinary electrochemical performances of Zn-Co-S@NSC were mainly ascribed to the synergistic effect of the various chemical composition, high electrochemically active surface area, and abundant active sites of the dodecahedral structure. These findings suggest that the bi-metallic sulfides derived from the metal-organic framework (MOF) can be a promising alternative as non-noble electrocatalysts towards ORR in the next generation of energy storage and conversion technologies.