A low-cost and efficient route for large-scale synthesis of NiCoSx nanosheets with abundant sulfur vacancies towards quasi-industrial electrocatalytic oxygen evolution.

[Display omitted] Transition-metal sulfides (TMS) have piqued a great deal of interest due to their unprecious nature and high intrinsic catalytic activity for water splitting. In this work, a low-cost and efficient route was developed, which included electrodeposition to prepare Ni-Co layered double hydroxide (NiCo-LDH) followed by ion exchange to form nickel cobalt sulfide (NiCoS x). Electrochemical reduction was used to modulate sulfur vacancies in order to produce sulfur vacancies-rich NiCoS x with nanosheet arrays on -three-dimensional nickel foam (NiCoS x -0.4/NF) with a large area of more than 250 cm2. Combining data from experiments and density functional theoretical (DFT) calculations reveals that engineered sulfur vacancies change the electronic structure, electron transfer property, and surface electron density of NiCoS x , significantly improving the free energy of water adsorption and boosting electrocatalytic activity. The developed NiCoS x -0.4/NF has long-term stability of more than 300 h at 500 mA cm−2 in 1 M KOH at ambient temperature and only needs a 289 mV overpotential at 100 mA cm−2. Remarkably, the synthesized electrocatalyst rich in sulfur vacancies, exhibits exceptional performance with a high current density of up to 1.9 A cm−2 and 1 A cm−2 in 6 M KOH and leads to overpotentials of 286 mV at 80 °C and 358 mV at 60 °C, respectively. The catalyst's practicability under quasi-industrial conditions (60 °C, 6 M KOH) is further demonstrated by its long-term stability for 220 h with only a 3.9 % potential increase at 500 mA cm−2. [ABSTRACT FROM AUTHOR]