Highly Selective, Defect-Induced Photocatalytic CO<sub>2</sub> Reduction to Acetaldehyde by the Nb-Doped TiO<sub>2</sub> Nanotube Array under Simulated Solar Illumination
Xinzhu Qian, Weiyi Yang, Shuang Gao, Jun Xiao, Swastik Basu, Anthony Yoshimura, Yunfeng Shi, Vincent Meunier, Qi Li
Abstract
The adsorption and activation of CO2 molecules on the surface of photocatalysts are critical steps to realize efficient solar energy-induced CO2 conversion to valuable chemicals. In this work, a defect engineering approach of a high-valence cation Nb-doping into TiO2 was developed, which effectively enhanced the adsorption and activation of CO2 molecules on the Nb-doped TiO2 surface. A highly ordered Nb-doped TiO2 nanotube array was prepared by anodization of the Ti–Nb alloy foil and subsequent annealing at 550 °C in air for 2 h for its crystallization. Our sample showed a superior photocatalytic CO2 reduction performance under simulated solar illumination. The main CO2 reduction product was a higher-energy compound of acetaldehyde, which could be easily transported and stored and used to produce various key chemicals as intermediates. The acetaldehyde production rate was over ∼500 μmol·g–1·h–1 with good stability for repeated long-time uses, and it also demonstrated a superior product selectivity to acetaldehyde of over 99%. Our work reveals that the Nb-doped TiO2 nanotube array could be a promising candidate with high efficiency and good product selectivity for the photocatalytic CO2 reduction with solar energy.