Ion modification of transition cobalt oxide by soaking strategy for enhanced water splitting

Heterostructure engineering carries prime importance to enhance the catalytic activity of electrocatalysts for water splitting. However, developing nonprecious metal oxides as splendid bifunctional electrocatalysts in alkaline conditions remains a great challenge. Herein, we developed a smart soaking strategy of sulfur/iron ion modification, by which we could activate Co₃O₄ to spontaneously form heterogeneous structure with excellent hydrogen/oxygen evolution reaction (HER/OER) performance. The nickel foam supported Co₃O₄ nanoarrays embellished with NiCoS_x (NiCoS_x@Co₃O₄ NAs/NF) was easily obtained via sulfur ion modification, which has rich oxygen vacancies and active sites, leading to an outstanding HER performance (η₁₀ = 59 mV, η₄₀₀ = 264.0 mV). Furthermore, Fe(Ⅱ) ion modified NiCoS_x@Co₃O₄ NAs/NF (FeNiCoS@Co₃O₄ NAs/NF) achieved superior OER performance (η₁₀ = 226 mV, η₄₀₀ = 302 mV) than other recently reported cobalt-based catalysts due to the synergistic activity of Ni-Fe-S-Co. More importantly, this work offered a facile and energy-free strategy for developing transition metal oxides as splendid bifunctional catalysts and contributed to the cost and energy savings and mass production for industrial applications as well as the design of advanced functional materials for energy chemistry.