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 CoO to spontaneously form heterogeneous structure with excellent hydrogen/oxygen evolution reaction (HER/OER) performance. The nickel foam supported CoO nanoarrays embellished with NiCoS (NiCoS@CoO NAs/NF) was easily obtained via sulfur ion modification, which has rich oxygen vacancies and active sites, leading to an outstanding HER performance (η = 59 mV, η = 264.0 mV). Furthermore, Fe(Ⅱ) ion modified NiCoS@CoO NAs/NF (FeNiCoS@CoO NAs/NF) achieved superior OER performance (η = 226 mV, η = 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.