ChemRxiv 2025 (Dhaka)

Change in the limiting free-energy span dGₘₐₓ(U) at U = 1.37 V vs RHE for undoped and different TM-doped Co3O4 systems. Bars represent the effect of different doping configurations: Undoped-Co3O4->Co (gold), Undoped-Co3O4->TM (turquoise), Co->TM (blue) and TM->2TM (orange). Negative values correspond to a reduction in Gₘₐₓ(U), which indicates a promoting effect of the respective dopant. Stars highlight the most favorable site configurations for each dopant.

Gmax(U) heatmap for OER on doped Co₃O₄(001), showing the free-energy span Gmax as a function of applied potential U and dopants (Cr, Mn, Fe, Ni, Cu, V). Lower Gmax indicates higher predicted activity.

Volcano plot for the oxygen evolution reaction on doped Co3O4(001) models with additional information on the preferred reaction mechanism (marked in blue) as derived from the scaling relationships ΔG*OOH vs ΔG*OH and ΔG*O vs ΔG*OH at an applied electrode potential of U = 1.37 V vs RHE. The solid line with shaded bands represents the predicted activity trends based on the scaling relationships, and the shaded area indicates uncertainty of the trend line based on the error bars of the scaling relationships. The vertical dashed lines mark transitions in the energetically favored reaction mechanism, and the preferred mechanistic description is given in each dG*O – dG*OH regime. Note that the symbols correspond to the DFT data for the different dopants (Cr, Fe, Ni, Mn, Cu, V, and undoped Co3O4) at different active sites.

Linear scaling relationships between the OER intermediates (*OH, *O, and *OOH) for pristine and TM-doped Co3O4. (a) dG*OH vs dG*OOH, (b) dG*O vs dG*OH and (c). dG*OOH vs dG*O. Each data point corresponds to a specific dopant atom (Fe, Ni, Cr, Mn, Cu, V, or undoped Co3O4) and an active site type (TM, Co, and 2TM). The fitted regression lines are shown with confidence intervals (shaded regions), along with the slope, intercept, and coefficient of determination (R2).