Improved Charge Separation and CO₂ Affinity of In₂O₃ by K Doping with Accompanying Oxygen Vacancies for Boosted CO₂ Photoreduction

The CO 2 photocatalytic conversion efficiency of the semiconductor photocatalyst is always inhibited by the sluggish charge transfer and undesirable CO 2 affinity. In this work, we prepare a series of K-doped In 2 O 3 catalysts with concomitant oxygen vacancies (O V ) via a hydrothermal method, followed by a low-temperature sintering treatment. Owing to the synergistic effect of K doping and O V, the charge separation and CO 2 affinity of In 2 O 3 are synchronously promoted. Particularly, when P / P 0 = 0.010, at room temperature, the CO 2 adsorption capacity of the optimal K-doped In 2 O 3 (KIO-3) is 2336 cm 3 ·g –1, reaching about 6000 times higher than that of In 2 O 3 (0.39 cm 3 ·g –1 ). As a result, in the absence of a cocatalyst or sacrificial agent, KIO-3 exhibits a CO evolution rate of 3.97 μmol·g –1 ·h –1 in a gas–solid reaction system, which is 7.6 times that of pristine In 2 O 3 (0.52 μmol·g –1 ·h –1 ). This study provides a novel approach to the design and development of efficient photocatalysts for CO 2 conversion by element doping.