Plasma-activated CoOx nanoclusters supported on graphite intercalation compounds for improved CO2 electroreduction to formate

Abstract

The CO₂ electroreduction reaction (CO₂RR) to chemicals and fuels is of both fundamental and practical significance, since it can lead to the more efficient storage of renewable energy and promote the carbon cycle. Here, the CO₂RR to formate over N₂-plasma-activated CoO_x/ZrO₂–graphite intercalation compounds was achieved with enhanced activity and selectivity, with a faradaic efficiency of 98.4% toward formate production and a current density of 8.2 mA cm⁻² at −0.35 V vs. RHE. A combination of experimental data and DFT calculations revealed that an increased Co²⁺ content on the surface of the CoO_x nanoclusters could reduce the energy barrier to the formation of *CO₂^δ−, which is the rate-determining step regarding the overpotential of the CO₂RR to formate. The π–π* bonds between the graphite layers, possessing the peculiar electronic structure of ZrO₂–graphite intercalation compounds, endowed the material with good electron transfer and fast carrier transport properties, and could help the formation of *OCHO to increase the selectivity for formate. This strategy provides a simple and efficient route to develop nanoclusters supported by graphite intercalation compounds for the CO₂RR to formate, with high selectivity and efficiency.