Study On Preparation Of Porous Nickel By Bubble Template Method

The dynamic hydrogen bubble template method is an efficient method for preparing porous metal materials by electrodeposition.The porous nickel materials prepared by this method have a micron-scale two-dimensional pore structure and can be applied to catalysis and sensing.This paper explores the evolution behavior of bubbles under different conditions in the method.By controlling the composition of the solution and the deposition conditions,the controlled growth of bubbles is achieved,and a nickel layer with a millimeter-level dilated pore structure is prepared,which can be used for vacuum adsorption molding molds.The manufacturing has high application value.Starting from the characteristics of bubble behavior in dilated pore research.The method of precipitation and merging of bubbles was further studied,and a three-dimensional porous nickel layer with a micron-level merged pore structure was prepared for the first time,and its performance in catalyzing hydrogen evolution was explored.The main contents are as follows:（1）Firstly,it is determined that the key factor for the formation of dilated holes in the deposition is the surface tension of the solution.The formation mechanism of dilated holes is explored,and the optimal composition of the solution is determined.The deposition with dilated holes is prepared on metal sheet with micro-holes,and the angle of the dilated hole profile can reach up to 50°.Using sodium dodecyl sulfate（SDS）to adjust the surface tension of the solution,and it is found that when the content of SDS is 0.005 g/L（surface tension is 50.2 m N/m）,it can not only form dilated holes at the micro-holes on metal sheet,but also reduce pinhole defects on the surface of the deposition.When the content of SDS is lower,the deposition can form holes at the position of the micro-hole,but there are a lot of pinhole defects in the remaining parts.When the content of SDS is higher than 0.005 g/L,no dilated holes can appear in the deposition.The morphology of the dilated pores in the deposition is affected by the concentration of H⁺in the solution,the stirring speed of the solution and the current density:after adding sulfamic acid,the hydrogen evolution reaction is enhanced,but the bubbles grow too fast and easily desorb,which is not conducive to the formation of dilated pores;The increase of stirring speed and current density can increase the angle of the vertebral foramen profile.The distance of the base hole also has an impact on the morphology of the dilated hole.If the distance between the micro-holes is too small,the growth of bubbles will compete,resulting in a smaller dilated hole in the deposition layer.（2）A combination of high and low current density is used to control the evolution of hydrogen.When the current density is low,the bubbles generated by electrodeposition will always adhere to the surface of the deposition;when the current density is high,there are dense gas generating active sites in the deposition layer,and the continuous overflow of bubbles makes the deposition form a dense porous structure.With nickel sulfamate（Ni（NH₂SO₃）₂·4H₂O）as the main salt,ammonium chloride（NH₄Cl）as the hydrogen source,when the concentration of NH4Cl is 3 M,electroplating with a current density of 1.000 A/cm² for 120 s;Then electroplating with a current density of 0.025 A/cm² for 10 hours can obtain a 3D porous nickel layer with a good combined pore structure,and the upper pore size is about 400μm.Compared with the two-dimensional porous nickel layer,the prepared 3D porous nickel layer has significantly improved catalysis of the hydrogen evolution reaction under alkaline conditions.