N-doped carbon networks as bifunctional electrocatalyst toward integrated electrochemical devices for Zn-air batteries driving microbial CO2 electrolysis cell

Abstract

A simple pyrolysis route has been developed for fabrication of nitrogen-doped carbon networks (N-Cnet) that not only features a large number of mesoporous structures, but also holds high specific surface area and excellent conductivity. The as-developed N-Cnet performs impressively toward electrocatalysis of oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR). For ORR in alkaline electrolyte, the N-Cnet manifests an initial potential of 0.95 V and half-wave potential of 0.86 V that are comparable to the benchmarked Pt/C catalysts. While for CO2RR, the N-Cnet shows a high selectivity for CO production with Faraday efficiency (FE) of as high as 95% and long-term stability. We further demonstrate the potential application of N-Cnet in electrochemical devices of zinc-air batteries (ZABs) and microbial CO2 electrolysis cell (MEC), the former is capable of releasing a maximum power density of 141 mW cm-2, while the later shows capability for efficiently converting CO2 into CO with the assistance of external voltage. We thus propose and set up an integrated proof-of-concept electrochemical device with ZABs driving MEC that can implement the feasibility of self-powered conversion of CO2 to value-added CO.