Effective Oxygen Reduction and Evolution Catalysts Derived from Metal Organic Frameworks by Optimizing Active Sites

Electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core materials in many renewable energy technologies including fuel cells, metal-air batteries, and water splitting devices. However, the high cost of the catalysts such as platinum and iridium oxide severely hinders the commercial development of these devices. Herein, we report a simple method for synthesizing effective bifunctional oxygen reduction and oxygen evolution catalysts through the rationally design of bimetallic metal organic framework precursor. The ratio of Zn and Co was optimized to search the critical factors affecting the catalysis of the ORR and OER. We found that for ORR catalysis, both Co/Co9S8 species and heteroatom-doped porous carbons played important roles. In contrast, the Co/Co9S8 species play more important role in OER catalysis. The optimized catalyst NSC-1-5 showed excellent ORR performance, with an onset potential of 0.879 V and a half wave potential of 0.81 V, as well as good OER catalytic activity. This was achieved simply by controlling the ratio of Co and Zn in the precursor, and NSC-1-5 could serve as a bifunctional catalyst for both ORR and OER. This work could shed some light on the design of bifunctional catalyst for both ORR and OER. (C) 2018 The Electrochemical Society.