Regulation of charge carrier migration in Cu2O/W18O49 S-scheme heterostructure for highly selective photocatalytic reduction of CO2 to HCOOH in water

The photocatalytic reduction of CO 2 and H 2 O to form formic acid (HCOOH) holds promise for meeting the carbon–neutral target. However, the reduced efficiency of carrier separation and the material’s vulnerability to photo-corrosion significantly impede its practical application. Herein, a 0D/1D Cu 2 O/W 18 O 49 S-scheme heterostructure is prepared by in situ growing Cu 2 O nanocrystals on W 18 O 49 ultrathin nanorods via the wet chemistry method. In situ irradiation X-ray photoelectron spectroscopy characterization uncovered the formation of a stable internal electric field (IEF) at the heterojunction interface between W 18 O 49 and Cu 2 O, which facilitates the separation of photon-generated carriers through an effective interfacial S-scheme transmission mechanism. Small-sized Cu 2 O (5–10 nm) anchored on the ultrathin W 18 O 49 nanorods exposes abundant active sites and enhances carrier separation while inducing electrons generated from W 18 O 49 to consume the holes in Cu 2 O, thus preventing the oxidation of Cu 2 O. The W 18 O 49 /Cu 2 O S-scheme heterostructure with the optimized composite ratio (40 % Cu:W) exhibited excellent performance in HCOOH production (56.42 μmol g −1 h −1 , 23.2-fold enhancement compared to pristine Cu 2 O) and 100 % selectivity for CO 2 photoreduction in water without any sacrificial reagents. This work provides a rational method for improving the stability of the catalyst and regulating charge carrier migration for highly selective CO 2 photoreduction in water.