Enhanced Adsorption Mediates Efficient CO₂ Reduction over a Ru/TiO_2–<i>x</i> Schottky Heterojunction

Photocatalytic reduction of CO2 offers a sustainable pathway toward the advancement of renewable energy and the resolution of environmental issues. The adsorption and activation of nonpolar CO2 molecules play a crucial role in the initial step of CO2 reduction for most semiconductor materials, making it a challenging task to design active sites on catalyst surfaces that can enhance CO2 adsorption. Herein, we propose oxygen vacancy (Vo)-regulated Ru/TiO2–x Schottky heterojunction nanomaterials with exceptional CO2 adsorption capacity and superior electron–hole separation ability as an advanced photocatalyst suitable for the photocatalytic reduction of CO2 with water. The incorporation of Vo to increase the physical adsorption capacity of CO2 by modulating catalyst surface charges, followed by constructing a Ru/TiO2–x Schottky heterojunction with Ru, further enhances chemisorption and activates CO2 while simultaneously improving water activation. Particularly, the incorporation of Ru in the form of Ru–O2– pairs serves as a catalyst for medium basic sites, attracting acidic CO2 molecules and thereby enhancing the chemical adsorption and dissociation capacity of CO2 on Ru/TiO2–x. Furthermore, the Schottky heterojunction induces directional migration of photogenerated electrons, facilitating the efficient separation of photogenerated charges and enhancing the utilization of photogenerated carriers. The synergistic interplay between Vo and metal Ru loading amplifies the photocatalytic performance of the Ru/TiO2–x catalyst, culminating in a remarkable CO generation rate of 224.6 μmol·g–1·h–1 under simulated sunlight irradiation, with an impressive selectivity of 81.6%. This study provides a novel strategy for preparing high-performance photocatalysts by the integration of bifunctional sites, aiming to enhance the CO2 adsorption efficiency in CO2 reduction.