Preparation And Electrocatalytic Activities For Water Splitting Of Nickel Foam-base Composite Materials

It is essential to develop new energy sources that can replace non-renewable fossil fuels and build a sustainable energy system while protecting the environment.Hydrogen is one of the most popular new energy sources.Driven by voltage,water can be completely decomposed into hydrogen and oxygen,so improving the efficiency of water electrolysis will undoubtedly play an important role in the conversion of renewable energy and the adjustment of energy system in the future.The development of transition metal electrocatalysts with abundant active sites plays an important role in the field of renewable energy.So far,many researchers have adopted methods such as designing nanostructures,adding conductive supports,or doping other elements to develop efficient electrochemical catalysts.Based on the above viewpoints and through experimental optimization,three multicomponent composite electrocatalysts based on transition metal foam nickel were prepared in this paper.The morphology,structure,element composition and electrolytic water performance of the catalyst were studied by a series of physical characterization and electrochemical tests.The main work is as follows:?1?Based on nickel foam,Mo S₂-Graphene-Ni O@Ni composite was synthesized by in-situ oxidation with hydrogen peroxide,loading molybdenum disulfide and graphene on Ni O@Ni substrate by sol pull impregnation and annealing at 500?for 4 h in Ar-H₂ atmosphere.The composite catalyst was characterized by means of XRD,SEM,TEM and XPS.The results showed that the surface of the catalyst formed compact pleated structure.The hydrogen evolution performance was tested in a three-electrode system and an alkaline electrolyte?1M KOH?by an electrochemical workstation.It showed an overpotential of 150 m V at 10 m A·cm^-2,the Tafel slope of 80 m V·dec^-1,and a charge transfer resistance(R_ct)is 15.14?and has good stability.?2?Mo Se₂/Ni Se/Ni₃Se₂@Ni composite catalyst material was synthesized in situ by one-step hydrothermal method using nickel foam as the substrate and nickel source,selenium powder,hydrazine hydrate and sodium molybdate as raw materials.By means of XRD,SEM,TEM and XPS,the composite catalyst was characterized,and the surface of the material formed the morphology of the interlaced particles and nano-sheets.The electrochemical workstation was used to test its electrolytic water performance in a three-electrode system,alkaline electrolyte?1M KOH?.For HER,the required overpotential and Tafel slope at 10 m A·cm^-2 are 113 m V and 85.7m V·dec^-1,respectively.As OER electrocatalysts,its overpotential is 397 m V and Tafel slope is 44.9 m V·dec^-1 at current density of 100 m A·cm^-2.In addition,when used as both cathode and anode for the overall catalytic cracking of water,it only needs a1.835 V battery voltage to reach a current density of 10 m A·cm^-2,which indicates its potential as a dual-function electrocatalyst for overall water cracking.?3?Based on foamed nickel,selenium dioxide and ammonium paramolybdate as raw materials,Mo Se₂@Ni was first prepared by electrochemical deposition,and then immersed in a 0.01 M iron nitrate nonahydrate solution by simple soaking at room temperature to grow Fe OOH-Mo Se₂@Ni composite catalyst material.The composite catalyst was characterized by means of SEM and XPS,and the nanorods were formed on the surface of the material.The electrochemical workstation was used to test its electrolytic water performance in a three-electrode system,alkaline electrolyte?1M KOH?.For HER,the required overpotential and Tafel slope of 10 m A cm^-2 were 128m V and 99.4 m V·dec^-1,respectively.For OER,at the current density of 20 m A·cm^-2,its overpotential is 306 m V and the Tafel slope is 67.8 m V·dec^-1.Both as hydrogen and oxygen evolution materials have more stable properties.