Rapid Self-Decomposition of g-C<sub>3</sub>N<sub>4</sub> During Gas–Solid Photocatalytic CO<sub>2</sub> Reduction and Its Effects on Performance Assessment
Peng Chen, Xing’an Dong, Ming Huang, Kanglu Li, Lei Xiao, Jianping Sheng, Si Chen, Ying Zhou, Fan Dong
Abstract
We report direct evidence of the rapid self-decomposition of graphitic carbon nitride (g-C3N4), a popular photo (electro) catalyst, during the gas–solid photocatalytic reaction. Crucially, the average rate of CO production from the light-induced self-decomposition of g-C3N4 in Ar is almost equal to that in a CO2 atmosphere, and the products of the self-decomposition include CO, CO2, NO2, and NO2–/NO3–. Using experimental and theoretical studies, we reveal that the chemical instability of g-C3N4 is related to the adsorbed hydroxyl groups (OHads) on the catalyst surface. Specifically, the electronic interactions between OHads and g-C3N4 reduce the stability of the C–N═C bonds, and photogenerated charge carriers attack the structural units of g-C3N4, leading to rapid decomposition. Theoretical calculations indicate that self-decomposition reaction is more thermodynamically favorable than CO2 reduction reaction. Overall, these findings demonstrate the importance of catalyst self-decomposition and the need to fully consider the products from catalyst instability when evaluating the gas–solid photocatalytic redox reaction performance.