Hydrophilic Ni3S2-MoN heterostructure on Ni foam (Ni3S2-MoN/NF) as an electrocatalyst for enhanced hydrogen evolution

In this study, a Ni3S2-MoN heterostructure was directly synthesized on a Ni foam support (Ni3S2-MoN/NF) through a facile one-step annealing process, using MoCl5 and thiourea at 450 °C under an N2 gas flow. The synthesized Ni3S2-MoN/NF catalyst achieved exceptional hydrogen evolution reaction (HER) activity, with low overpotential values of 154.3 mV (η50) at 50 mA cm-2 and 186.3 mV (η100) at 100 mA cm-2 in 1.0 M KOH. The enhanced HER performance was attributed to the synergistic effect between the highly active Ni3S2-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 H2O and OH, facilitating water dissociation. Additionally, MoN was found to induce structural modifications in Ni3S2, enhancing the hydrogen binding energy and thereby improving the HER activity. Furthermore, the inherently hydrophobic Ni3S2 surface was transformed into a hydrophilic Ni3S2-MoN surface, further enhancing the HER activity. In a 24 h stability test at 100 mA cm-2, the HER activity of Ni3S2-MoN/NF improved, due to the partial conversion of Ni3S2 into amorphous Ni(OH)2 species, resulting in a reduction of overpotential by 30 mV (η50 = 125.5 and η100 = 158.2 mV). This simple and economical synthesis method highlights the potential of Ni3S2-MoN/NF as a promising catalyst for the HER with high activity and stability.