Preparation And Electrochemical Performance Of Co-Based Alloy HER Catalytic Electrode

With the rapid development of the global economy and the increasing demand of energy,the environment problem is increasingly serious.It is imperative to promote the exploitation of friendly and sustainable alternative energy.Hydrogen as a kind of high density,clean and renewable energy,has attracted widespread attention due to its high calorific value,no pollution,and wide range of sources.It is of great significance to study the non-noble metal catalysts with high catalytic activity for cathodic hydrogen evolution reaction,to improve the efficiency of electrolysis water,and reduce energy consumption.This paper mainly focuses on the preparation of hydrogen evolution catalytic electrode of Co-based alloys and its electrocatalytic properties in alkaline media.The main research contents are given as follows.(1)Co-W alloy coatings were prepared on Cu substrates by galvanostatic electrodeposition,which are amorphous if the concentration of WO42-?0.075mol·L-1.Electrochemical analysis showed that the amorphous Co-W alloy coatings exhibited excellent electrocatalytic activity for hydrogen evolution reaction(HER)in 1 mol·L-1 NaOH solution.The HER occurs though a Volmer-Heyrovsky reaction pathway.The S-4 coating(W content is 40.1wt.%)showed the best HER activity and its apparent exchange current density j0 equaling 3.17×10-5A·cm-2 and the Tafel slope equaling 84.3 mV· dec-1.Moreover,the cathode current density of the S-4 coating exceeds of commercial Pt when the applied potential more negative than-1.464Vvs.SCE.In addition,EIS results suggested that the high HER activity of the amorphous Co-W alloy coatings were mainly attributed to both the high intrinsic catalytic activity and the large specific surface area.(2)Based on the study of the Co-W alloy coatings,the Co-W/porous Cu composite coatings were prepared by galvanostatic electrodeposition on the surface of porous Cu that was fabricated by the "Bubble Template Method".The composite coatings were porous,greatly increasing the specific surface of the electrode.Compared with the Co-W alloy coatings,the electrocatalytic hydrogen evolution activity of the Co-W/porous Cu composite coatings were improved.When the concentration of WO42-was 0.1 mol·L-1 in the bath,the prepared Co-W/porous Cu composite coating(sample P-4)exhibited the highest electrocatalytic activity.its apparent exchange current density j0 reaching 1.59× 10-4 A cm-2,which is significantly higher(about 5 times)than the Co-W alloy coatings(3.17×10-5 A· cm-2),the Tafel slope is 78.8 mV·dec-1.And the hydrogen evolution pathway is as same as the Co-W alloy coatings.Both the Co-W alloy coatings and the Co-W/porous Cu composite coatings exhibited excelent stability.(3)The Co-Ni-B/CC composite electrodes were prepared by in situ growth of Co-Ni-B alloy on carbon cloth(CC)though chemical reduction.The Co-Ni-B alloy has an amorphous structure,and as a self-supporting electrode,the Co-Ni-B/CC composite electrodes exhibited excellent electrocatalytic performance for HER in 1 mol ·L-1 NaOH solution.When the ratio of Co to Ni is 1:1(sample Co-50Ni-B/CC),showed the best HER activity and its apparent exchange current density j0 equaling 9.77×10-4 A·cm-2.When the applied potential was more negative than-1.343Vvs.SCE,the cathode current density of the Co-50Ni-B/CC exceeds of commercial Pt/C.The Tafel slope is 88.7 mV·dec-1,and the HER occurs though a Volmer-Heyrovsky reaction pathway.The cyclic LSV test and constant potential polarization results showed that the Co-Ni-B/CC electrode had good stability in 1 mol·L-1NaOH solution,and maintained high catalytic activity during the test process.All of the three kinds of electrocatalytic electrode showed high HER activity and good stability in 1 mol·L-1 NaOH solution.The HER occurs though a Volmer-Heyrovsky reaction pathway and the high catalytic activity could be maintained during the test.Among them,the Co-W/porous Cu composite coating(P-4)exhibited the best electrocatalytic activity.The Co-Ni-B/CC self-supporting electrode with the excellent electrocatalytic activity electrocatalytic activty whose preparation process was the easiest,has a certain practical application prospect.