Ultrasmall C-TiO2−x nanoparticle/g-C3N4 composite for CO2 photoreduction with high efficiency and selectivity

Abstract

The photoreduction of CO₂ to CO offers a promising sustainable and clean approach for a global new energy program. Coupling this reductive process with a matched water photo-oxidation pathway is an attractive avenue to accelerate the half-reaction of CO₂ reduction. Herein, we propose a three-component photocatalyst design strategy for reducing CO₂ to CO coupled with water oxidation via a two-electron/two-step pathway. Employing polyoxotitanium ([Ti₁₇O₂₄(OPrⁱ)₂₀]) as a titanium source, ultrasmall TiO_2−x nanoparticles coated with ultrathin carbon layers (C-TiO_2−x) were fabricated and loaded on to a g-C₃N₄ matrix through chemical bonding (C-TiO_2−x@g-C₃N₄) for the first time. The optimized C-TiO_2−x@g-C₃N₄ photocatalyst showed a very high activity of 12.30 mmol g⁻¹ (204.96 mmol g TiO₂ ⁻¹) CO generation within 60 h visible-light irradiation, which represents the highest CO production rate to date among the reported TiO₂-based materials under similar conditions. The excellent adsorption capability of C-TiO_2−x@g-C₃N₄ for photons, H⁺ protons, and CO₂ molecules together with efficient charge separation and the two-electron/two-step oxidative pathway lead to the high reactivity.