Strong photo-thermal coupling effect boosts CO₂ reduction into CH₄ in a concentrated solar reactor

This study is dedicated to solving the problems of low energy utilization and low yield in the conventional photocatalytic CO₂ reduction process. Herein, we constructed a novel concentrated solar (light) reactor and enabled the titanium foam-based monolithic photocatalyst TF@TNT/0.4CoO_x-0.1CuO to improve the solar energy utilization efficiency and CO₂ conversion rate by concentrating light and its thermal effect. We found that the yield of CH₄ increased up to 220 times (from 0.53 µmol/cm² to 116.4 µmol/cm²) when the light intensity of the reactor was increased from 400 mW/cm² to 4266 mW/cm² (10.6 times). Meanwhile, the solar-to-fuel conversion efficiency was improved up to 0.35% in the concentrated solar (light) reactor. We further investigated the origin of the photothermal coupling effect with concentrated light through the electrochemical and photochemical measurements. It shows that the concentrated light can further lower the reaction barrier (from 41.62 to 31.51 kJ/mol) and the induced photothermal coupling effect could significantly increase the yield. This provides a valuable strategy for the efficient and environmentally friendly utilization of CO₂ using solar energy.