Surface Acidity-Activity Relationships in Transition-Metal Oxides Probed by NH₃-TPD for the Oxygen Evolution Reaction...

Identifying general descriptors that control oxidation catalysis remains a significant challenge in catalyst design. Here, we report, for the first time, a direct correlation between surface acidic site strength and catalytic performance for a series of transition-metal oxides (Mn₂O₃, Fe₂O₃, Co₃O₄, NiO and RuO₂). Across photochemical OER, electrochemical OER and biomass-derived molecule oxidation, all catalysts exhibit an identical activity sequence: RuO₂ > Co₃O₄ > NiO > Fe₂O₃ > Mn₂O₃, mirroring their acidity profiles as determined by NH₃-TPD. Catalysts with an optimal ratio of medium-acidic sites exhibit faster proton-coupled electron transfer (PCET) kinetics, lower overpotentials and improved charge-transfer properties during oxidation reactions. Glycerol oxidation, along with glucose, HMF, furfural and lignin oxidation on Co₃O₄, also follows this acidity-driven behaviour, confirming the generality of the correlation. No relationship is observed between activity, particle size or surface area, indicating that intrinsic surface chemistry, rather than morphology, dictates reactivity. These results establish surface acidic site strength as an important descriptor for oxidation catalysis, providing a practical framework for designing next-generation, multifunctional catalysts.