A Zn–CO2 Flow Battery Generating Electricity and Methane

Abstract

AbstractMetal–CO2 batteries represent an economical and efficient CO2 utilization technique, which provides a mechanism combining CO2 reduction with electricity generation instead of electricity input. Existing metal–CO2 batteries generally work in a closed system by recycling CO2. In this study, a flow battery is designed with a hollow fiber of carbon nanotubes (cathode), Zn wire (anode), and 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (electrolyte). The battery can continuously consume CO2 to produce CH4 under ambient conditions and promptly output the gaseous product through the hollow fiber, with a Faradaic efficiency up to 94%. Simultaneously, the battery generates electricity, with an energy density of 288.3 Wh kg−1 (based on the zinc mass) and a stability up to 8 days. The high selectivity and efficiency of the battery is attributed to a water‐shuttling assisted proton mechanism and delicate electrode–electrolyte interplay. Moreover, the Zn anode is electrochemically renewed and the battery assembled with the regenerated Zn anode restores battery performances to the former level. The renewable characteristic implies that, if the regeneration of Zn anode is coupled to excessive renewable energy sources, then the Zn–CO2 flow battery will be promising to accomplish a net reduction of CO2 emission.