Study On Hydrogen Evolution Activity And DFT Calculation Of Ni-Mo-P Nanocomposite Electrode

Massive environment pollution by consuming conventional fossil fuels imminently drives people to search for renewable,eco-friendly and renewable energy resources.Water electrolysis is a significant and ideal approach to produce hydrogen among all the technologies for generating hydrogen,which is regarded as the best way to the hydrogen economy.Pt,Pd and their alloys exhibit the best catalytic activity for hydrogen evolution reaction（HER）.However,large scale applications are hindered due to their high cost and scarcity.Therefore,it is significant to explore and design a highly active,low overpotential cathodic hydrogen evolution catalytic material which can largely reduce energy-consumption.In this paper,the research on the preparation,electrocatalytic performances and DFT calculation of nickel-based hydrogen evolution electrodes have been systematically reported.The main results are as follows:（1）A novel nanostructured Ni-Mo-P planar electrode was successfully developed via feasible combing electric spark deposition（ESD）and phosphorization method.During physical characterization,it can be stated that Ni₁₂P₅ is the major phase on the surface of Ni-Mo-P electrode.The sample exhibits a foliated nanosheet-like structure,acquiring not only its large specific surface area,but also expose more active sites.The electrocatalytic results show that the as-fabricated Ni-Mo-P electrode possesses lower overpotential,higher current density and less Tafel slope than pristine modified Ni@Ni-Mo in 1.0 M KOH and also shows long-term stability.An overpotential as low as 276 mV can achieve 100 mA cm^-2 H₂ evolving current density,being superior to most of previously reported samples.（2）To further explore an in-depth understanding on the activity enhancement mechanism,we performed density functional theory（DFT）calculations on the electronic structure and Gibbs free-energies of Ni@Ni-Mo and Ni-Mo-P electrodes.Firstly,we calculated the H adsorption energy and Gibbs free-energy of all possible sites on Pt（111）and Ni（111）surface.Next,we calculated the H adsorption energy,Gibbs free energy,and the density of state（DOS）,density differential charge and bader charge at optimal positions on different surfaces of Ni₁₂P₅ and Ni₄Mo.According to the DFT calculation,the Gibbs free-energy of the Ni₁₂P₅ is-0.16 eV,being lower than Ni（-0.24 eV）and Ni₄Mo（-0.209 eV）.The DFT result also confirms the HER catalytic sequence follows Pt>Ni₁₂P₅>Ni₄Mo>Ni,which is consistent with the experimental results.