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

The CO₂ photocatalytic conversion efficiency of the semiconductor photocatalyst is always inhibited by the sluggish charge transfer and undesirable CO₂ affinity. In this work, we prepare a series of K-doped In₂O₃ 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 CO₂ affinity of In₂O₃ are synchronously promoted. Particularly, when P/P₀ = 0.010, at room temperature, the CO₂ adsorption capacity of the optimal K-doped In₂O₃ (KIO-3) is 2336 cm³·g^-1, reaching about 6000 times higher than that of In₂O₃ (0.39 cm³·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 In₂O₃ (0.52 μmol·g^-1·h^-1). This study provides a novel approach to the design and development of efficient photocatalysts for CO₂ conversion by element doping.