Density functional theoretical study of the tungsten-doped In₂O₃ catalyst for CO₂ hydrogenation to methanol

Indium oxide is a promising catalyst for CO₂ hydrogenation to methanol and has been extensively investigated in recent years. However, the studies on doped In₂O₃ for methanol synthesis are relatively few, and tungsten-doped In₂O₃ has not been reported yet. Herein, the mechanism of the methanol synthesis from CO₂ hydrogenation on the defective W-doped In₂O₃ model (W-In₂O₃_D) has been investigated via density functional theory (DFT) calculations. The oxygen vacancy on the In₂O₃ catalyst is essential for the activation and conversion of CO₂. The introduction of tungsten results in higher electron density and electron localization on the oxygen vacancy, thus facilitating the activation of CO₂. The methanol synthesis on the W-In₂O₃_D model takes the formate route via the H₃CO intermediate. Compared with the In₂O₃_D model, the cleavage of the C-O bond, the removal of H₂O*, and the conversion of HCOO* are promoted by the addition of W. Based on the energetic span model, the turnover frequency (TOF) for the methanol synthesis from CO₂ hydrogenation on the W-In₂O₃_D model is predicted as 9.0 × 10^-3 s^-1, which is much higher than the TOF of 4.5 × 10^-6 s^-1 on the In₂O₃_D model. Overall, the introduction of tungsten makes the CO₂ hydrogenation to methanol kinetically more favorable.