Sulfur and oxygen dual vacancies manipulation on 2D NiS2/CeO2 hybrid heterostructure to boost overall water splitting activity

It is still an enormous challenge to develop non-precious electrocatalysts through low-cost and efficient methods. To fulfill highly active site exposure and optimized intrinsic activity, the 2-dimensional NiS₂/CeO₂ with unique heterostructure and abundant sulfur and oxygen vacancies (v-NiS₂/CeO₂ HS) was prepared by solvothermal reaction and annealing. The density functional theory calculations illustrate that the materials with both heterostructure and vacancies simultaneously have a positive effect on promoting the kinetics of oxygen evolution reaction and hydrogen evolution reaction and optimizing the adsorption energy of hydrogen. As a result, v-NiS₂/CeO₂ HSs deliver the current density of 10 mA/cm² at the low overpotential of 271 mV for oxygen evolution reaction and the overpotential required by v-NiS₂/CeO₂ HSs for hydrogen evolution reaction is 123 mV (at 10 mA/cm²). The v-NiS₂/CeO₂ HSs demand a lower cell voltage with 1.64 V (at 10 mA/cm²) toward overall water splitting. These results provide a theoretical and practical direction for the development of low-cost, earth-abundant electrocatalysts.