Chestnut-like Molybdenum-Doped Nickel Cobaltite Spinel Oxide Nanoparticles Grown on Ni Foam as the Electrocatalyst for the Hydrogen Evolution Reaction

The 3D NiMo_xCo_2-xO₄ (x ≤ 0.06) chestnut-like spinel oxide nanoparticles (CNSPs) grown on Ni foam were effectively prepared hydrothermally. The formation of Ni-Co CNSPs was confirmed by the XRD powder pattern, which exhibited a pure cubic spinel oxide structure without undesired phases. All ratios revealed a broadened peak representing a small crystal size (12.8-17.5 nm) range. The chestnut-like CNSPs were presented by FE-SEM, SEM, TEM, and HR-TEM analysis. The chemical composition of the products was confirmed by EDX. The 3D NiMo_xCo_2-xO₄ (x = 0.04) CNSP electrocatalyst exhibited hydrogen evolution reaction (HER) activity as evidenced by 0.224 V overpotential, Tafel slope 61.9 mV/dec, and high stability for 36 h of chronopotentiometry techniques. The surface and electrochemical characterization revealed that 4.0% Mo-doped exhibits improved HER activity due to significantly higher electrochemical surface area and accelerated charge-transfer kinetics at the semiconductor electrolyte interface. Density functional theory is employed to investigate the impact of Mo dopants on the HER performance. This study shows how both hydrogen and water molecules adhere to the surface of Mo-doped NiCo₂O₄ slab structures. The findings indicate that introducing Mo dopants leads to an augmentation of chemical activity through water adsorption, resulting in an enhanced electrocatalytic process and improved HER activity up to a specific Mo concentration, and their impact on spin-dependent electronic structure characteristics is revealed by the density of states spectra. This work not only gives insights into low-metal-cost materials for efficient and durable HER electrocatalysts, but it also provides a successful showcase model catalyst for in-depth mechanistic insights into electrochemical HER processes and their industrial applications in the future.