rGO modified R-CeO2/g-C3N4 multi-interface contact S-scheme photocatalyst for efficient CO2 photoreduction

Highlights: • 2D-1D-2D g-C₃N₄/R-CeO₂/rGO photocatalyst has been prepared for CO₂ photoreduction. • 2D-1D-2D multi-interface contact structure is of help for carrier transfer process. • π-π conjugation effect and Ce⁴⁺/Ce³⁺ transformation facilitate electron transmission. • In-situ FTIR and ¹³C isotope tracer tests analysis the CO₂ photoreduction mechanism. Construction of multi-interface contact step-scheme (S-scheme) photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photocatalytic CO₂ reduction. In this paper, g-C₃N₄ nanosheets were selected as the main photocatalyst, rod-like CeO₂ (R-CeO₂) with unique Ce⁴⁺→Ce³⁺ conversion property and rGO were loaded on the g-C₃N₄ surface to construct 2D-1D-2D sandwich photocatalyst. The yields of CO and CH₄ were about 63.18 and 32.67 μmol/g after 4 h when the rGO/R-CeO₂/g-C₃N₄ was used as catalyst, which were about 4 and 6 times higher than that of pure CN, respectively. Cyclic experiments proved that the composite had excellent photocatalytic and material stability. Photoelectrochemical tests showed that the construction of S-scheme electron transfer model and the introduction of rGO can great enhance the electron transmission and separation of photogenerated electron-hole pairs. CO₂ adsorption test identified that the loading of R-CeO₂ and rGO obviously enhanced the CO₂ adsorption ability of pure g-C₃N₄. Density functional theory (DFT) calculations used to analyze the electron transfer path and the formation of the build-in electric field at the semiconductor interface. In-situ FTIR and ¹³CO₂ element-tracer detection carried out to research the process of CO₂ photoreduction. A possible multi-interface contact S-scheme electron transfer mechanism for enhanced CO₂ photoreduction activity has been discussed.