In-plane heterostructured MoN/Mo2N nanosheets as high-efficiency electrocatalysts for alkaline hydrogen evolution reaction

Economical and efficient electrocatalysts are crucial to the hydrogen evolution reaction (HER) in water splitting to produce hydrogen. Heterostructured electrocatalysts generally exhibit enhanced HER catalytic activity due to the strong electron coupling effects and synergistic optimization of hydrogen adsorption–desorption. Herein, in-plane heterostructured MoN/Mo2N nanosheets are fabricated as high-efficiency HER electrocatalysts in the alkaline medium from bulk MoS2 by molten salt-assisted synthesis. Density-functional theory calculations and experiments show that the in-plane heterostructured MoN/Mo2N nanosheets facilitate interfacial electron redistribution from Mo2N to MoN, giving rise to more negative H2O adsorption energy and optimal hydrogen adsorption free energy (ΔGH* = −0.017 eV). Consequently, a low overpotential of 126 mV at 10 mA cm−2 and a small Tafel slope of 69.5 mV dec−1 are achieved in the 1M KOH electrolyte, demonstrating excellent HER characteristics. Moreover, the overpotential shows negligible change after operating at 50 mA cm−2 for 12 h, confirming the excellent stability. The results reveal a novel and effective strategy to design highly efficient 2D in-plane heterostructured HER electrocatalysts for water splitting.