Understanding the Contrasting Effects of V vs Mn Doping on the OER Activity of Co3O4(001): A DFT+ U Study

Abstract Designing efficient electrocatalysts for clean energy conversion requires atomic-scale insight into the relationship between targeted surface modifications and catalytic performance. Using density functional calculations with an on-site Hubbard U term (DFT+U), we investigate the effect of Mn and V doping on the performance of Co3O4(001) as an anode material for the oxygen evolution reaction (OER). Our results show that Mn, which is preferentially incorporated at a surface octahedral site at both the B- and A-terminated Co3O4(001) surfaces, has a detrimental effect on the OER efficiency. In contrast, V, which also prefers a surface octahedral site at the B-layer termination, acquires a 5+ oxidation state and reduces the overpotential (η) of a Cooct reaction site from 0.48 to 0.43 V. Remarkably, at the A-termination, V is incorporated as V4+ in the subsurface layer, which reduces the overpotential at the tetrahedral Co site from 0.74 to 0.18 V. This enhancement in catalytic activity is attributed to the modification of the surface Cooct oxidation state from Co3+ (IS) to Co2+ prior to OER and its further variation during OER. This substantially reduces the binding energy of *OH and thereby the potential-determining step height by 0.56 eV. Taking into account implicit solvation increases the overpotential for both undoped and Mn-doped surfaces, whereas it marginally decreases the overpotential for the V-doped A-layer termination. The deprotonation of *OH to *O constitutes the potential-determining step for all investigated surface reaction sites, thereby positioning them on the right leg of the volcano plot, while η of the Cotet reaction site at the V-doped A-layer lies beyond the top of the volcano. These insights demonstrate how selective doping can be used as a promising strategy to tailor catalyst’s performance.