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

Abstract

The photocatalytic reduction of CO₂ and H₂O 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 Cu₂O/W₁₈O₄₉ S-scheme heterostructure is prepared by in situ growing Cu₂O nanocrystals on W₁₈O₄₉ 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 W₁₈O₄₉ and Cu₂O, which facilitates the separation of photon-generated carriers through an effective interfacial S-scheme transmission mechanism. Small-sized Cu₂O (5–10 nm) anchored on the ultrathin W₁₈O₄₉ nanorods exposes abundant active sites and enhances carrier separation while inducing electrons generated from W₁₈O₄₉ to consume the holes in Cu₂O, thus preventing the oxidation of Cu₂O. The W₁₈O₄₉/Cu₂O S-scheme heterostructure with the optimized composite ratio (40 % Cu:W) exhibited excellent performance in HCOOH production (56.42 μmol g⁻¹h⁻¹, 23.2-fold enhancement compared to pristine Cu₂O) and 100 % selectivity for CO₂ 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 CO₂ photoreduction in water.