A hydrophilic NiS-MoN heterostructure on Ni foam (NiS-MoN/NF) as an electrocatalyst for enhanced hydrogen evolution in alkaline media.

In this study, a NiS-MoN heterostructure was directly synthesized on a Ni foam support (NiS-MoN/NF) through a facile one-step annealing process, using MoCl and thiourea at 450 °C under an N gas flow. The synthesized NiS-MoN/NF catalyst achieved exceptional hydrogen evolution reaction (HER) activity, with low overpotential values of 154.3 mV () at 50 mA cm and 186.3 mV () at 100 mA cm in 1.0 M KOH. The enhanced HER performance was attributed to the synergistic effect between the highly active NiS-MoN heterostructure and the NF support, which offers a large surface area and excellent electrical conductivity. Density functional theory (DFT) calculations reveal that MoN strongly adsorbs HO and OH, facilitating water dissociation. Additionally, MoN was found to induce structural modifications in NiS, enhancing the hydrogen binding energy and thereby improving the HER activity. Furthermore, the inherently hydrophobic NiS surface was transformed into a hydrophilic NiS-MoN surface, further enhancing the HER activity. In a 24 h stability test at 100 mA cm, the HER activity of NiS-MoN/NF improved, due to the partial conversion of NiS into amorphous Ni(OH) species, resulting in a reduction of overpotential by 30 mV ( = 125.5 and = 158.2 mV). This simple and economical synthesis method highlights the potential of NiS-MoN/NF as a promising catalyst for the HER with high activity and stability.