Developing an efficient and inexpensive electrocatalyst is of paramount importance for realizing the green hydrogen economy through electrocatalytic water splitting. Here, we demonstrated a facile large-scale, industrially viable binder-free synthesis of Zn-doped NiS electrocatalyst on bare nickel foam (NF) through a hydrothermal technique. The present catalyst, i.e., nickel sulfide (NiS) nanosheets on nickel foam with optimized doping of Zn atom (Zn–NiS-3), displays excellent catalytic efficacy for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It requires an overpotential of 320 mV for OER at a current density of 50 mA cm⁻² and an overpotential of 208 mV for HER at a current density of 10 mA cm⁻². The water electrolyser device having Zn–NiS-3 electrocatalyst as both cathode and anode show excellent performance, requiring a cell voltage of only 1.71 V to reach a current density of 10 mA cm⁻² in an alkaline media. The density functional theory (DFT) based calculations showed enhanced density of states near Fermi energy after Zn doping in NiS and attributed to the enhanced catalytic activities. Thus, the present study demonstrates that Zn–NiS-3@NF can be coined as a viable electrocatalyst for green hydrogen production.