Synergistically engineering of vacancy and doping in thiospinel to boost electrocatalytic oxygen evolution in alkaline water and seawater

Electronic structure engineering lies at the heart of the catalyst design, however, utilizing one strategy to modify the electronic structure is still challenging to achieve optimal electronic states. Herein, an advanced approach that incorporating both Ru dopants and sulfur vacancies into thiospinel-type FeNi2S4 to synergistically modulate the electronic configuration, is proposed. Deep characterizations and theoretical study reveal that the in-situ formed Ni3+ species are real active centers. Ru doping and sulfur vacancies synergistically tune the electronic states of Ni2+ sites to a near-optimal value, leading to the formation of abundant oxygen evolution reaction (OER)-active Ni3+ species via electrochemical reconstruction. Consequently, the optimized Ru-FeNi2S4 catalyst can exhibit superb electrocatalytic performance towards OER, delivering the overpotentials of 253 mV and 340.8 mV at 10 mA·cm−2 in alkaline water and seawater, respectively. The proper combination of vacancy and heteroatom doping in this work may unlock the catalytic power of conventional catalysts toward electrochemical reactions.