(321g) Theoretical Insights into the Role of Peroxo Intermediates in Alternative Anodic Reactions

Our recent analysis of oxygen bonding strength in transition metal oxides has revealed a broad spectrum of reactivities, characterized by a V-shaped behavior associated with the filling of anti-bonding states. For transition metals with electron configurations ranging from d⁰ to d¹⁰, oxygen reactivity is generally weak [1]. While the oxygen evolution reaction (OER) is well-established for metal oxides with moderately bonded oxygen, for instance: IrO₂ and RuO₂ the chemistry of weakly bonded metal oxides is considerably less explored. At the same time, photo-electrochemical solar fuel devices, such as those developed by the Liquid Sunlight Alliance (LiSA), stand to gain significantly from exploring alternative anodic reactions to OER, potentially yielding valuable anodic products.

Promising reactions currently under investigation include water oxidation to peroxide, epoxidation of light olefins [2], and alcohol oxidation reactions [3]. In this study, we conduct a theoretical analysis to re-evaluate the weakly bonded region, identifying the transition from oxo-bonded species to peroxo species, a switch previously observed in systems like TiO₂. We compute the overall energetics of these reactions and determine which reactive oxygen species is most favorable for each alternative reaction. Finally, we discuss the fundamental feasibility and limitations of these anodic reactions in comparison to OER.

This material is based on work performed by the Liquid Sunlight Alliance, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266.

[1] ACS Catal. 2024, 14, 5286–5296.

[2] Science 2024, 383 (6678), 49–55.

[3] ACS Catal. 2023, 13 (7), 4272–4282.