▎ 摘　　要

Three-dimensional (3D) porous carbon-based materials with tunable composition and microstructure are of great interest for the development of oxygen involved electrocatalytic reactions. Here, we report the synthesis of 3D porous carbon-based electrocatalyst by self-assembling Co-metal organic frameworks (MOF) building blocks on graphene via a layer-by-layer technique. Precise control of the structure and morphology is achieved by varying the MOF layer to tune the electrocatalytic properties. The as-produced electrocatalyst exhibits an excellent catalytic activity for the oxygen reduction reaction in 0.1 mol L-1 KOH, showing a high onset potential of 0.963 V vs. reversible hydrogen electrode (RHE) and a low tafel slope of 54 mV dec(-1), compared to Pt/C (0.934 V and 52 mV dec(-1), respectively). Additionally, it shows a slightly lower potential vs. RHE (1.72 V) than RuO2 (1.75 V) at 10 mA cm(-2) in an alkaline electrolyte. A rechargeable Zn-air battery based on the as-produced 3D porous catalyst demonstrates a high peak power density of 119 mW cm(-2) at a cell voltage of 0.578 V while retaining an excellent stability over 250 charge-discharge cycles. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.