Spontaneously producing syngas from MFC-MEC coupling system based on biocompatible bifunctional metal-free electrocatalyst

Abstract

The preparation of high-value fuels and chemicals through the electrochemical carbon dioxide reduction reaction (CDRR) is of great significance to the virtuous cycle of carbon dioxide. However, due to the high overpotential involved in this reaction, high power consumption and high-cost noble-metal-based catalysts are required for driving this process. Herein, the electrochemical CDRR was achieved on biocompatible metal-free nitrogen, phosphorus co-doped carbon-based materials (NP-C) in the microbial fuel cell-microbial electrolysis cell (MFC-MEC) coupling system. As the bioelectrochemistry in MFC supplied power to drive the electrocatalysis in MEC, syngas was spontaneously produced from this coupling system without external energy input. With the NP-C materials as the excellent bifunctional electrocatalyst for the CDRR and oxygen reduction reaction (ORR), the current density of the MEC reached −0.52 mA cm−2, and the Faradaic efficiencies (FEs) of CO and H2 were 60% and 40%, respectively, at a load resistance of 10 Ω. Moreover, the CO/H2 product ratio can be changed by adjusting the load resistance, which will widely meet various demand of syngas usage in further reactions. This study provides a spontaneous and tunable production of syngas in biogas digesters via a electrochemical strategy.