Trends of Electrochemical CO₂ Reduction Reaction on Transition Metal Oxide Catalysts

Density functional theory calculations were used to explore reactivity trends of the electrochemical CO₂ reduction reaction (CO₂RR) toward methanol, methane, methanediol, and formic acid on 12 transition metal dioxide (TMO) surfaces in their rutile structure. The (110) facet of the TMOs was used as a model system to investigate the thermodynamic limiting potentials of CO₂RR. Activity and selectivity volcano plots for various products were obtained through the scaling relations of adsorbed intermediates. RhO₂ is predicted to be a good catalyst for production of formic acid with low onset potential of around -0.2 V. In addition to its high activity, hydrogen evolution reaction (HER) is predicted to not limit its efficiency due to weak hydrogen binding free energy on this oxide. CrO₂ is another promising candidate for CO₂RR with onset potential of around -0.3 V toward most of the products. CrO₂ seems to be more interesting than RhO₂ for production of methanol, methane, and methanediol as it adsorbs HCOOH on its surface in a dissociated form. CrO₂ is also predicted to be more selective toward these CO₂RR products than toward forming hydrogen gas.