چكيده انگليسي :
In this work, the electrocatalytic characteristics of a binary electroless Ni-P coating and a ternary electroless Ni-P-M coating (M being W, Mo, and Co in this study) were examined. Electrochemical investigations on Ni-P binary coating revealed that the sample with a medium phosphorus percentage (MP) coated at a pH of approximately 4.6 and an amorphous-crystalline structure had the best electrocatalytic capabilities. According to all the results so far, it was found that among the Ni-W-P coatings, sample WH16 with η10 = -181, η20=-208, and η100=-415, among Ni-Mo-P coatings, sample MH0.4 with η10 = -181, η20=-202, and η100=-342 and among the Ni-Co-P coatings, sample CH10 with η10 = -132, η20 = -175 and η100 = -305, had the lowest overpotential and the best electrocatalytic properties. Despite the obvious improvement in electrocatalytic properties, a comparison with the electrodes produced by other researchers revealed that the electrodes produced in this study had little kinetics of hydrogen evolution; consequently, electrodes containing three alloy elements (Ni-W-Mo-P, Ni-Mo -Co-P, and Ni-Mo-Co-P) and four alloy elements (Ni-W-Mo-Co-P) were successfully produced via the electroless method. The presence of alloy components in the coating was confirmed by SEM/EDS analysis. For a more thorough study, XRD tests were conducted on the samples, revealing that the structure of the quaternary and quinary coatings had altered from crystalline to amorphous. The LSV test revealed that the quaternary and quinary samples had superior electrocatalytic properties compared to the remaining samples. The kinetics of hydrogen generation increased (from the lowest kinetics to the highest kinetics) from the Ni-W-Mo-P samples (with η10 = -115, η20 = -136 and -208 η100) to the Ni-Mo-Co-P samples (with η10 = - 100, η20 = - 121 and η100=-196) and Ni-Mo-Co-P samples (with η10 = - 79, η20 = - 94 and η100=-154). The results of the quaternary samples were promising; however, the Ni-W-Mo-Co-P quinary sample was also successfully coated. The LSV results showed that the sample had η10 = - 41, η20 = - 46, and η100=-67 had higher hydrogen production kinetics compared to other samples and were comparable to the findings of other researchers. The Ni-W-Mo-Co-P sample exhibited the fastest hydrogen generation kinetics, as determined by the cyclic voltammetry test results and the normalized LSV curves plotting. Electrochemical impedance spectroscopy (EIS) experiments were conducted on MP samples, the best ternary samples (WH16, MH0.4, and CH10), quaternary samples (Ni-W-Mo-P, Ni-Mo-Co-P, and Ni-Mo-Co-P) and quinary samples (Ni-W-Mo-Co-P). The EIS results were found to be in good agreement with the LSV results, and the sample (Ni-W-Mo-Co-P) with a resistance of 6 Ω×Cm2 was featured with the fastest kinetics in this test. The stability of the produced electrodes was evaluated by chronopotentiometry, step chronopotentiometry, cyclic voltammetry, and LSV before and after 1000 cycles of voltammetry, and the findings demonstrated that all samples produced by the electroless approach were stable. Considering that all the samples were stable, but the Ni-W-Mo-Co-P sample had the highest kinetics, this sample was selected as the ideal sample. This sample contained nickel, tungsten, molybdenum, cobalt, and phosphorus, as confirmed by XPS examination. Molecular Dynamics Simulations were performed to validate the results of electrochemical measurements. After obtaining the ideal sample structures through simulations, the Ni-W-Mo-Co-P sample was found to have the lowest ∆G.
