Visible Light-Driven Highly Selective CO2 Reduction to CH4 Using Potassium-Doped g-C3N5

Establishment of an efficient and robust artificial photocatalytic system to convert solar energy into chemical fuels through CO₂ conversion is a cherished goal in the fields of clean energy and environmental protection. In this work, we have explored an emergent low-Z nitrogen-rich carbon nitride material g-C₃N₅ (analogue of g-C₃N₄) for CO₂ conversion under visible light illumination. A significant enhancement of the CH₄ production rate was detected for g-C₃N₅ in comparison to that of g-C₃N₄. Notably, g-C₃N₅ also showed a very impressive selectivity of 100% toward CH₄ as compared to 21% for g-C₃N₄. The photocatalytic CO₂ conversion was performed without using sacrificial reagents. We found that 1% K doping in g-C₃N₅ enhanced its performance even further without compromising the selectivity. Moreover, 1% K-doped g-C₃N₅ also exhibited better photostability than undoped g-C₃N_5. We have also employed density functional theory calculation-based analyses to understand and elucidate the possible reasons for the better photocatalytic performance of K-doped g-C₃N₅.