One-step Electrodeposition of Ni-Mo-Nd/NF Electrodes and Their Hydrogen Evolution Performance

Finding non-precious metal hydrogen evolution reaction (HER) electrocatalysts with high efficiency and low cost is a great challenge. One-step galvanostatic deposition method was used to prepare nickel-molybdenum-neodymium ternary hydrogen evolution electrode on nickel foam substrate and improve its hydrogen evolution performance under alkaline condition. The effects of process parameters on the performance of Ni-Mo-Nd/NF hydrogen evolution electrode were studied by electrochemical workstation, and the Ni-Mo/NF hydrogen evolution electrode was prepared simultaneously. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface morphology, phase structure, element content and bonding state of the alloy coating. The hydrogen evolution performance was measured by linear sweep voltammetry (LSV), Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Throughout the electrodeposition experiment, the NF (10 mm×10 mm×0.3 mm), the graphite plate (20 mm×20 mm×5 mm) and the saturated calomel electrode (SCE) were used as working, counter, and reference electrodes, respectively. The results showed that the optimum process parameters were pH=4.5, current density 30 mA/cm2, deposition time 60 min and temperature 30 ℃. After electrochemical deposition, the surface of Ni-Mo/NF alloy coating presented cellular structure with relatively coarse particles. With the introduction of Nd element, the surface particles of Ni-Mo-Nd/NF coating increased, and the fine particles grew directly on the conductive substrate, which increased the specific surface area of the coating, provided more the active sites of hydrogen evolution, and helped to improve hydrogen evolution efficiency. According to Mapping, Ni, Mo and Nd were evenly distributed on the coating, and their mass percentages were 57.0%, 29.9% and 13.1% respectively. It could be seen from XRD that with the doping of Mo and Nd, the peak appeared negative shift, which might be due to the solid solution of Mo and Nd in Ni, and the Ni atom was replaced by the Nd atom with a larger radius, and the lattice changed. Ni 2p, Mo 3d and Nd 3d peaks could be clearly observed in the XPS total spectrum. In terms of electrochemical performance, the over potential of Ni-Mo-Nd/NF was only 73 mV at 10 mA/cm2 in alkaline medium, the Tafel slope was 147 mV/dec, the double-layer capacitance (Cdl) value was 4.39 mF/cm2, the charge transfer resistance was 1.352 Ω, compared with Ni-Mo/NF. The binary electrode decreased by 62 mV, 54 mV/dec, 0.35 Ω, and the double-layer capacitance (Cdl) value increased by 1.66 mF/cm2. In addition, the current density of Ni-Mo-Nd/NF electrocatalyst remained stable after prolonged electrolysis for 24 h, and the activity of the catalyst decreased slightly after 2 000 cycles of voltammetry. It is concluded that the doping of rare earth element Nd can increase and refine the crystal grains, thus increasing the specific surface area of the electrode, providing more active sites for hydrogen evolution reaction and improving the efficiency of hydrogen evolution reaction. Compared with the binary alloy Ni-Mo/NF, the Ni-Mo-Nd/NF ternary alloy electrode exhibits better HER catalytic performance due to the synergistic effect of the ternary alloy. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.