The Missing Link for Electrochemical CO Reduction: Classification of CO vs HCOOH Selectivity via PCA, Reaction Pathways, and Coverage Analysis

For the electrochemical CO reduction reaction, different metal catalysts preferentially produce different products. However, the differences between the metals’ reaction pathways that lead to these different products are still not fully understood. In this work, we analyze CO vs HCOOH formation from CO using statistical analysis and density functional theory calculations. This is carried out by considering multiple descriptors, along with competing reaction pathways, reaction barriers, and high coverage of mixed adsorbates on the surface. This method is capable of explaining the discrepancy between simulations and experiments regarding Ag and Au selectivity and of properly classifying elements according to their product distribution. We find that, when considering water-assisted protonation for the disproportionation to CO, Ag and Au have a lower barrier for CO production in agreement with experimental results. We also find that, when considering the high coverage of mixed adsorbates on the Ag and Au surfaces, the most stable adsorbate configuration contains adsorbates capable of forming CO preferentially. These findings help to bridge the gap between simulations and experiments and provide a missing link for our understanding of the CO reduction reaction.