In situ doped CoCO3/ZIF-67 derived Co-N-C/CoOx catalysts for oxygen reduction reaction

Fuel cell is one of the new energy sources that attracts much attention at present. However, it is still a great challenge to develop novel oxygen reduction reaction (ORR) catalysts with low cost and high activity. In this work, Co-N-C/CoOx carbon matrix composites were synthesized using in-situ mixtures of CoCO3 and ZIF-67 as precursors. CoCO3 is formed by the reaction of Co2+ with carbonate in solution, at the same time, ZIF-67 is gradually formed on its surface, CoCO3 crystals can be synchronously incorporated into ZIF-67 structure. In the other hand, the 2-MI could avoid the aging of CoCO3 crystals and form larger particles. Finally, ZIF-67/CoCO3 composite structure material is formed. Because of the existence of CoCO3 crystals, ZIF-67/CoCO 3 carbonization at 800 degrees C in N-2 atmosphere can form CoOx -doped Co-N-C structure. In the carbonization process of CoCO3 will produce a series of effects on the carbon-based structure of the material, making it more conducive to the ORR catalytic reaction. Therefore, the obtained Co-N-C/CoOx exhibits ORR performance comparable to commercial 20% Pt/C in alkaline medium, and its stability and methanol tolerance are far superior to commercial 20% Pt/C.