Porous CuBi2O4 Photocathode with Intrinsic Cu+/Cu2+ Redox Improves Solar C(sp3)‐H Bond Conversion Efficiency by an Order of Magnitude

Abstract Selective C‐H activation is the most important step for organic molecule transformation. Photocatalytic radicals driven C‐H activation is considered a promising route but suffers from simultaneously utilizing electron/hole pairs which are limited to broad‐band gap semiconductors. Herein, a half‐photocathodic reaction strategy is demonstrated to activate and oxygenate C(sp 3 )‐H bonds of toluene toward selective benzaldehyde production using a narrow‐bandgap CuBi 2 O 4 (CBO) porous photocathode. The intrinsic Cu + /Cu 2+ redox of porous CBO photocathode catalyzes the photocathodic oxygen reductive H 2 O 2 to generate ·OH capable of oxidation which activates the C(sp 3 )‐H bond that is further oxygenated via ·O 2 − formed of the photocathodic oxygen reduction. As a result, the benzaldehyde selectivity is up to 90%. Impressively, the narrow‐band gap of CBO enables record‐high light‐driven benzaldehyde yields of 111.93 mmol m −2 h −1 with stability of over 20 h. This work opens a green and efficient light‐driven C(sp 3 )‐H bond oxidation strategy by using a narrow‐bandgap photocathode.