Preparation Of Phosphide Nickel Composite Nanomaterials For Electrocatalytic Water Splitting

The global energy crisis and its associated environmental issues have created an urgent need for clean,cheap and renewable energy.Hydrogen is known as the clean energy of the 21st century and regarded as an ideal energy source.It is attracting more and more people's attention due to its high energy density and environmental protection.Electrocatalytic water splitting can realize the convenient and large-scale production of hydrogen from abundant water sources.At present,Pt-based and IrO₂,RuO₂-based precious metal materials have been proved to be the most effective electrocatalysts for hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?,respectively.However,their insufficient content and high cost on the earth greatly limit their wide application.Therefore,it is very urgent to develop a catalyst with low cost,high efficiency and good stability to replace precious metals.The ideal electrode material should have good electrical conductivity,high electrocatalytic activity,large specific surface area,excellent corrosion resistance,and the transition metal phosphide can meet the most of these requirements owing to the interstitial compound formed by the phosphorus atom entering the transition metal lattice.In this thesis,a transition metal phosphide nanomaterial catalyst with a single metal and multi-metal heterostructure were grown on a foamed nickel with three-dimensional pore frame by hydrothermal and low-temperature phosphorization methods?1?Porous Ni₂P nanosheets were prepared by phosphating high-density nickel hydroxide precursor nanosheets obtained by hydrothermal method.This simple and low-cost preparation method allows the Ni₂P electrode material to have multiple active sites and superior film-based binding ability.Electrochemical behavioral tests have found that an overpotential of 139 mV is required for a cathode current density of 10mA cm^-2 under alkaline conditions,and its hydrogen evolution overpotential is superior to most other homogeneous materials.It also shows excellent stability under the high current density of industrial prodution.?2?Based on the above work,the porous Ni₂P nanosheets were grown on the foamed nickel by the same method.Then,NiFe LDH nanosheets were deposited on the Ni₂P nanosheets to form NiFe LDH and Ni₂P by adjusting the parameters of the electrodeposition process.The composite structure further increases the specific surface area and active sites of the nanomaterial.The electrochemical tests demonstrated that the oxygen evolution potential of this composite structure has been significantly improved.?3?In order to investigate the effect of multi-transition metal phosphide on electrocatalytic performance,bimetallic heterostructure phosphorus of Cu₃P and Ni₂P was successfully prepared by hydrothermal method and low temperature phosphorization method on foam nickel.It was found by electrochemical tests that the special nano-morphology and electronic structure of the bimetallic phosphide have a significant effect on the electrocatalytic performance,and the hydrogen evolution performance is only 108 mV overpotential at a current density of 10 mA cm^-2 which is lower than that of Ni₂P?150 mV?and Cu₃P?200 mV?indicating that the possible couple and synergistic enhancement effects.