Fundamental Research On The Method And Application Of Additive Manufacturing Of Nickel-based Dendritic Electrode

Hydrogen energy as a kind of efficient clean energy has been highly concerned by society.Electrolysis of water is one of the simplest methods for hydrogen production.However,the existing electrolytic water technology for hydrogen production has the problems of low efficiency,high-energy consumption and high cost.Meanwhile,the catalytic electrode is the most important part of hydrogen production technology by electrolysis of water.Its structure and material properties have a great influence on the efficiency and cost of hydrogen production.The traditional preparation technology generally adopts the foamed metal or carbon-based framework as the skeleton,and the precious metal catalyst is deposited on its surface to produce hydrogen.However,this method has many problems,such as complicated preparation process,high cost and poor stability,which will seriously affect the practical industrial application of catalytic electrode in water electrolysis technology.Therefore,it is very important to develop a new type of highly efficient self-supporting catalytic electrode for hydrogen production.In view of this key problem,this paper carries out the topic“Fundamental Research on the Method and Application of Additive Manufacturing of Nickel-based Dendritic Electrode”with systematic and in-depth theoretical and experimental exploration,and obtains a series of innovative achievements with important theoretical significance and energy application value.(1)A rapid additive manufacturing technology for Ni-based dendritic electrodes was firstly proposed.Based on the local current enrichment effect and the dynamic template effect of hydrogen bubble,this technology can be used for rapid additive manufacturing of dendritic metal structures by jet electrodeposition method.It has the advantages of high additive efficiency,simple process and equipment,and stable deposition process.At the same time,through to the annular nozzle structure and multi-axis linkage control system,and visual man-machine interface design and development,this paper puts forward the interelectrode feedback current servo motor control strategy,develops a nickel-based dendrite type of electrode material manufacturing platform,and realizes the automatic operation of additive manufacturing of dendrite electrode,to ensure the dynamic stability manufacturing process of nickel-based dendrite electrode.(2)Macro jet finite element model is built under the environmental solution flow and charge distribution based on the theory of electric field and flow field between two electrodes.The influence law of flow field in relations between the poles are analyzed via different pole spacing,the anode rod diameter and initial solution velocity.Distribution regularity of charge accumulation on the surface of cathode is got through the distance between the poles and initial voltage.Based on the coarse-grained molecular dynamics method,the micro-electrodeposition behavior of dendritic electrode assisted by flow field was firstly simulated,and the influence mechanism of potentiostatic and pulsed electrical parameters on the micro-growth process and deposition morphology of dendritic structure under strong convection environment was revealed.(3)Through constructing vertical distributed three electrode test system assisted by injection,this paper studies the different nickel base material manufacturing solution composition on the influence law of dendrite-shape electrochemical deposition behavior relationship,and establishs depositional model of the electrode in the stationary state and the vertical distribution with jet flow,then,gets the mathematical equations of initial state of nickel atoms deposition nucleation and growth.Based on the coarse-grained molecular dynamics model,combined with the nucleation diffusion and growth conditions of the deposited ions,the influence of different growth environments on the microscopic nucleation growth of the electrode was simulated and analyzed,revealing the dynamic deposition characteristics of the dendritic structure in the process of jet electrodeposition.(4)The influence law of macro-micro morphology is studied by the solution flow rate,solution temperature and feedback current of dendrite electrode parameters.Further using SEM,TEM and XRD characterization method,the type electrical parameters on the dendrite microstructure and physical properties of the electrode are found out to obtain the optimal jet electrodeposition process parameters,namely solution velocity:1.1 m/s,solution temperature:32℃,feedback current 1.2 A,pulse duration time:10μs,pulse interval time:35μs,peak voltage:26 V.Combined with the electrocatalytic performance test and hydrophilic/hydrophobic characteristics analysis,it is proved that the dendritic electrode has excellent performance of oxygen evolution and hydrogen evolution,and benefited by the unique dendritic porous structure,it has achieved good hydrophilic/hydrophobic ability.(5)The surface structure of dendritic electrode is etched and modified by one-step pickling with hydrochloric acid solution.The effects of solution temperature and concentration of hydrochloric acid on the morphology of the electrode during etching are investigated,and the changes of microstructure and physical characteristics of the composite electrode are also analyzed.It is found that a large number of nanospherical particles are uniformly attached on the surface of the dendritic electrode,and 2D/3D composite dendritic electrode with oxygen vacancy modification is prepared for the first time.Profited from the unique multi-dimensional distribution structure,the 2D/3D composite dendritic electrode shows excellent oxygen evolution performance.The oxygen evolution current density of 100m A/cm~2 can be generated at a low overpotential of 330 m V,which is much better than the precious metal iridium dioxide electrode(100 m A/cm~2@390 m V).Combined with density functional theory(DFT)calculations,the intrinsic catalytic activity of the composite dendritic electrode doped with oxygen vacancy is also revealed.(6)Fluorine element is infiltrated into the surface of the dendritic electrode by electrochemical fluorination etching.By exploring the influence of etching process parameters on the dendrite structure,the change rule of microphysical characteristics of the dendrite electrode before and after etching is analyzed.The results show that a hollow dendritic electrode structure has been prepared for the first time after electrochemical fluorination etching.Benefited by exposing the double surfaces of the inner and outer walls of the electrode skeleton,the contact area between the dendritic electrode and the solution is greatly expanded,and the mass transfer of solutes in the electrode is accelerated.When the current density of hydrogen evolution is-10 m A/cm~2,the electrode shows an ultra-low overpotential of 13 m V,which is better than the precious metal platinum carbon electrode(-10m A/cm~2@57 m V).Combined with experimental and theoretical analysis,the excellent catalytic performance of hollow dendritic electrode co-doped with fluorine element and oxygen vacancy is proved.