A Nonaqueous Mg‐CO2 Battery with Low Overpotential

Abstract

AbstractMg‐CO2 batteries, which exploit the greenhouse gas CO2 as cathode active species, are an appealing next‐generation battery candidate due to their high efficiency energy storage and value‐added CO2 utilization. However, compared with other metal‐CO2 systems, few aprotic Mg‐CO2 batteries have been reported so far as a result of several crucial problems including the comparatively slow redox reaction kinetics, a large decomposition energy barrier of the reduction products, and poor reversibility in their multi‐electron three‐phase cathodic reactions in nonaqueous environments. Herein, a rechargeable Mg‐CO2 battery is developed by using a Mo2C‐CNTs catalytic cathode, a nonaqueous electrolyte, and a magnesium metal anode. The Mo2C‐CNTs catalytic cathode can greatly reduce the charge overpotential of the Mg‐CO2 battery through tuning the CO2 reduction pathways. The results of a variety of ex situ and in situ experiments as well as theoretical calculations show the Mo2C catalyst not only induces surface molecular adsorption for faster reaction kinetics but also improves the selectivity toward MgC2O4 in the CO2 reduction process for a higher Faraday efficiency. An exceptional low voltage hysteresis is achieved for the Mg‐CO2 battery. This work demonstrates a promising strategic option for rechargeable nonaqueous Mg‐CO2 batteries for simultaneously addressing energy and environmental issues.