Atomic-Layer-Deposited MoNx Thin Films on Three-Dimensional Ni Foam as Efficient Catalysts for the Electrochemical Hydrogen Evolution Reaction

Future realization of a hydrogen-based economy requires a high-surface-area, low-cost, and robust electrocatalyst for the hydrogen evolution reaction (HER). In this study, the MoNx thin layer is synthesized on to a high-surface-area three-dimensional (3D) nickel foam (NF) substrate using atomic layer deposition (ALD) for HER catalysis. MoNx is grown on NF by the sequential exposure of Mo(CO)6 and NH3 at 225 °C. The thickness of the thin film is controlled by varying the number of ALD cycles to maximize the HER performance of the MoNx/NF composite catalyst. The scanning electron microscopy and transmission electron microscopy (TEM) images of MoNx/NF highlight that ALD facilitates uniform and conformal coating. TEM analysis highlights that the MoNx film is predominantly amorphous with the nanocrystalline MoN grains (4 nm) dispersed throughout it. Moreover, the high-resolution (HR)-TEM analysis shows a rough surface of the MoNx film with an overall composition of Mo0.59N0.41. X-ray photoelectron spectroscopy...