Regulating the OCCHO intermediate pathway towards highly selective photocatalytic CO reduction to CHCHO over locally crystallized carbon nitride

• Published in: Energy & environmental science 2022-01, Vol.15 (1), p.225-233
• Main Authors: Liu, Qiong, Cheng, Hui, Chen, Tianxiang, Lo, Tsz Woon Benedict, Xiang, Zhangmin, Wang, Fuxian
• Format: Article
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d1ee02073k

Photocatalytic conversion of CO 2 to CH 3 CHO is of increasing interest but confronts the significant challenges of forming C-C bonds and keeping the C&z.dbd;O bond intact throughout the process. Here, we report the selective photocatalytic hydrogenation of CO 2 to CH 3 CHO using a modified polymeric carbon nitride (PCN) under mild conditions. The locally crystallized PCN offers a photocatalytic activity of 1814.7 μmol h −1 g −1 with a high selectivity of 98.3% for CH 3 CHO production and a quantum efficiency of 22.4% at 385 nm, outperforming all the state-of-art CO 2 photocatalysts. The promoted formation of the *OCCHO intermediate on the locally crystallized PCN is disclosed as the key factor leading to the highly selective CH 3 CHO generation. The locally crystallized PCN favors spontaneous C-C coupling towards *OCCHO formation rather than *CHO protonation, thus preventing HCHO formation. This work provides a new strategy for designing carbon nitrides for highly selective and sustainable conversion of CO 2 to CH 3 CHO. Locally crystallized PCN is prone to form *OCCHO groups rather than *CH 2 O groups, regulating the endoergic C-C coupling step to a simultaneous exoergic reaction and changing the reaction pathway towards CH 3 CHO (selectivity of 98.3%) instead of HCHO.