Photo-to-Thermal Conversion Harnessing Low-Energy Photons Renders Efficient Solar CO₂ Reduction

Efficient photocatalytic solar CO₂ reduction presents a challenge because visible-to-near-infrared (NIR) low-energy photons account for over 50% of solar energy. Consequently, they are unable to instigate the high-energy reaction necessary for dissociating C═O bonds in CO₂. In this study, we present a novel methodology leveraging the often-underutilized photo-to-thermal (PTT) conversion. Our unique two-dimensional (2D) carbon layer-embedded Mo₂C (Mo₂C-C_x) MXene catalyst in black color showcases superior near-infrared (NIR) light absorption. This enables the efficient utilization of low-energy photons via the PTT conversion mechanism, thereby dramatically enhancing the rate of CO₂ photoreduction. Under concentrated sunlight, the optimal Mo₂C-C_0.5 catalyst achieves CO₂ reduction reaction rates of 12000-15000 μmol·g^-1·h^-1 to CO and 1000-3200 μmol·g^-1·h^-1 to CH₄. Notably, the catalyst delivers solar-to-carbon fuel (STF) conversion efficiencies between 0.0108% to 0.0143% and the STF_avg = 0.0123%, the highest recorded values under natural sunlight conditions. This innovative approach accentuates the exploitation of low-frequency, low-energy photons for the enhancement of photocatalytic CO₂ reduction.