First-principles study of CO₂ hydrogenation on Cd-doped ZrO₂: Insights into the heterolytic dissociation of H₂.

This article focuses on the theoretical investigation of cadmium (Cd)-doped zirconia (ZrO₂) catalysts for the selective hydrogenation of carbon dioxide (CO₂) to methanol using density functional theory (DFT) calculations. The study reveals that Cd doping significantly facilitates the formation of oxygen vacancies on the ZrO₂ surface, which enhances CO₂ adsorption and activation by creating unsaturated oxygen sites (Omob). Hydrogen (H₂) adsorption is more challenging and primarily occurs via heterolytic dissociation forming compact ion pairs such as [H_Cd–H_O]*, which lower energy barriers for subsequent hydrogenation steps. The reaction proceeds predominantly through the formate (HCOO*) pathway, with key intermediates undergoing sequential hydrogenation and isomerization steps leading to methanol formation, while competing pathways producing CO are kinetically and thermodynamically less favorable. The presence of oxygen vacancies and Cd doping modulates the electronic structure and active sites, improving catalytic activity and selectivity toward methanol, with microkinetic modeling supporting high turnover frequencies under relevant reaction conditions.