Revisiting Factors Controlling the Electrochemical CO₂ Reduction to CO and HCOOH on Transition Metals with Grand Canonical Density Functional Theory Calculations

Abstract

The design of highly selective catalysts to form a single product represents one of the biggest challenges in electrochemical carbon dioxide reduction reactions (eCO 2 RR). However, the controversial and simplified mechanistic studies hinder the proposal of effective principles guiding rational catalyst design. Herein, by using grand canonical density functional theory (GC-DFT) calculations and the hybrid solvent model, we revisited the reaction mechanism of two-electron eCO 2 RR on a group of transition metals with an emphasis on illustrating why gold favors CO while Indium favors HCOOH. We identified the potential difference (U d ) between the onset potential for stable ∧-shaped *CO 2 − formation (U ∧-CO2 ) and the potential of zero charge system (U PZC−CO2 ) as a crucial indicator for the selective HCOOH production, representing a good addition to the criteria via a binding strength comparison of *COOH and HCOO* species. Our results not only deepen the mechanistic understanding of the two-electron eCO 2 RR process on metals at different potentials but also provide effective guidance for rational catalyst design to produce HCOOH selectively.