Increasing Oxygen Vacancies by Incorporating Co into Nano ZnO for Selective Hydrogenation of CO2 into Methanol

Abstract

CO₂ to methanol is considered a promising method for CO₂ conversion and utilization, yet achieving desirable selectivity remains a significant challenge. Herein, efficient CO₂ hydrogenation to methanol is achieved by synthesizing Co_0.7ZnO with abundant oxygen vacancies (O_v) through the incorporation of a portion of Co into nanoscale ZnO. By tuning the molar ratio of Co/(Co+Zn) in Co_xZnO to increase the O_v content to 71%, CO₂ adsorption and activation to form formate (COOH*) are enhanced, thereby reducing the CO selectivity. The efficiency of the hydrogenation of CO₂ to methanol was optimized with Co_0.7ZnO, which exhibited an impressive methanol formation rate of 2.1 mmol/(g h) and a selectivity of up to 96.7%. The unique structure of incorporating partial Co into nanoscale ZnO to increase the level of O_v not only reduces the level of CO selectivity but also inhibits methane formation, thereby contributing to the high methanol selectivity. This study presents an innovative strategic design through partial doping, which is essential for controlling the selectivity of target products in the CO₂ hydrogenation.