Regulating the electronic structure of CoMoO4via La doping for efficient and durable electrochemical water splitting reactions

Abstract

Metal molybdates (M′MoO₄, M = Fe, Co, and Ni) are recognized as active catalysts for water-splitting reactions. However, their poor electronic conductivity and low intrinsic activity hamper overall water-splitting activity and durability, limiting their widespread applications. Herein, the influence of lanthanum doping on the electrocatalysis of CoMoO₄ toward overall water-splitting activity and durability in high-pH media was investigated. Varying La-dopant percentages in the CoMoO₄ lattice tuned the electrocatalytic activity, and optimal performance was achieved at 5% La_CoMoO₄ for hydrogen (η₂₀ at 0.219 V_RHE) and oxygen evolution reactions (η₂₀ at 0.272 V_RHE). Notably, La doping in CoMoO₄ mitigated significant MoO₄²⁻ leaching in the electrolyte, maintaining excellent structural integrity and demonstrating high durability for over 45 h in a two-electrode system, demanding a cell potential of only 1.68 V toward overall water splitting in 1 M KOH. Structural characterizations and in situ Raman studies established a dynamic surface reconstruction of active components toward the HER/OER. DFT analyses proved the modified electronic structure of CoMoO₄ through La doping, effectively optimizing adsorption energies of reactive hydrogen and oxygen intermediates and boosting the intrinsic activity of CoMoO₄ toward hydrogen and oxygen evolution reactions (HER/OER). This work depicts the prospect of rare-earth metal incorporation in non-noble metal-based electrocatalysts to design highly efficient and durable electrocatalysts for electrochemical applications.