In Situ Electronic Redistribution Tuning of NiCo2S4 Nanosheets for Enhanced Electrocatalysis

Metal Ru and vacancy engineering play an important role in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, there are few reports targeted on electrocatalysts by simultaneously employing these two strategies. Herein, theoretical calculation firstly predicts that Ru and VS can regulate the adsorption energy of OER/HER intermediates for NiCo2S4 electrocatalysts. Then, a facile solvothermal-photochemical strategy is utilized to synthesis series NiCo2S4 samples: through filling the solvothermal-created VS in NiCo2S4–x with Ru single atoms (Ru-NiCo2S4–x) under ultraviolet irradiation as OER catalysts. Besides, Ru nanoclusters are introduced into NiCo2S4 without VS (Ru-NiCo2S4) for HER. As a result, the OER exchange current density of NiCo2S4–x is prominently boosted after decoration of Ru single atom, which possesses an eminently low overpotential of 190 mV@50 mA cm−2, while Ru-NiCo2S4 shows superior HER performance (32 mV@10 mA cm−2) compared with Ru-NiCo2S4–x, surpassing most reported electrocatalytic materials. Moreover, Ru-NiCo2S4–x//Ru-NiCo2S4 exhibits remarkable stability and catalytic performance in the overall water splitting, with a cell voltage value of 1.46 V at 10 mA cm−2 in 1.0 m KOH. Bader charge analysis unravels the “restricted-delocalized-restricted” phenomenon between electrons promote the electron interactions, which in turn improves electrochemical performance.