Seeing the light: The role of cobalt in light-assisted CO2 methanation

Illuminating thermal catalysts with visible light is an effective strategy to reduce the thermal requirements of CO2 methanation. In this study, we systematically varied the cobalt properties and loading of xCo/CeO2 catalysts (between 0 and 10 wt.%) to understand changes in the visible light-assisted reaction mechanism with cobalt loading. 10Co/CeO2 had the highest CO2 conversion of 90% at 450 °C. The light promoted the CO2 conversion of all catalysts from 300 – 450 °C, peaking for 7.5Co/CeO2 with a 125% improvement relative to thermal conditions (300 °C) before diminishing for 10Co/CeO2. The light facilitated the conversion of the formate intermediate adsorbed onto CeO2. In-situ DRIFTS and DFT unveiled a particle size trade-off between maximising CO2 adsorbed at the Co-Ce interface while minimising CO2 adsorbed onto cobalt, which is required for the best light enhancement. These findings underscore the importance of careful deposit size optimisation to unlock the light-assisted methanation's full potential.