Doping BO_x-type transition metal oxides, where B (e.g., Co, Ni, Fe, Mn) prefers six-fold oxygen coordination, into Cu²⁺-based AO_x lattices, where Cu²⁺ favors four-fold coordination, results in local lattice strain and under-coordinated B sites. These strained environments can promote stronger oxygen binding, resulting in easier O─O bond cleavage. Cu-rich Cu[M]O_x/Au catalysts exemplify this design principle for ORR catalysts.

Abstract

The development of efficient and selective oxygen reduction reaction (ORR) catalysts is central to advancing electrochemical energy technologies. While platinum remains the benchmark, its high cost, peroxide selectivity, and durability issues demand alternatives. Transition metal oxides (TMOs) are promising in alkaline media, yet their ORR activity is hampered by weak oxygen binding and high activation barriers. This concept article introduces a coordination mismatch strategy to enhance ORR performance in mixed-metal oxides, specifically Cu[M]O_x (M═Co, Ni, Fe, Mn). By combining metals with differing oxygen coordination preferences, Cu²⁺ (four-fold) and Mⁿ⁺ (typically six-fold), local lattice strain and undercoordinated sites are introduced, enhancing O₂ adsorption and O─O bond cleavage. Cu-rich compositions, especially Cu_0.8Co_0.2O_x/Au, demonstrate high ORR activity, low H₂O₂ yield, and excellent stability. In situ Raman spectroscopy confirms stable M─O─Cu frameworks and redox-active Cu centers. The approach is validated across multiple dopants and supported by DFT studies showing stabilized OOH* intermediates and favorable energetics. These findings demonstrate that coordination engineering is a powerful strategy for designing efficient, selective, and robust nonprecious metal catalysts for electrochemical energy conversion.