Highly Efficient Photocatalytic CO2 Methanation over Ru-Doped TiO2 with Tunable Oxygen Vacancies

Solar-driven CO2methanation is an imperative and promising approach to relieve the global warming and environmental crisis,yet remains a great challenge due to the low reaction efficiency,unsatisfactory selectivity and poor stability.In this work,we demonstrate a facile and efficient strategy to prepare Ru-doped TiO2photocatalyst with tunable oxygen vacancies using the ascorbic acid as a reducing agent for the CO2methanation reaction.The optimal Ru-TiO2-OV-50 exhibits a remarkable CH4production rate of 81.7 mmol g-1h-1with a 100%CH4selectivity under a 1.5 W cm-2light illumination,which is significantly higher than commercial Ru/TiO2and other reported catalysts.We reveal that the superior photocatalytic CO2methanation performance is mainly due to the synergistic effect of Ru doping and TiO2with tunable oxygen vacancies.Impressively,the light rather than thermal effect is confirmed as the main influencing factor by experimental studies.In addition,in situ spectroscopic technology is performed to investigate the CO2methanation reaction pathway.This work will open an avenue to design and prepare highly efficient photocatalyst with tunable oxygen vacancies for CO2conversion and other related applications.