Study On Preparation And Electrocatalytic Performance Of Cobalt-nickel-based Non-noble Metal Electrocatalysts

Environmental pollution and energy shortage are the major problems in modern society.As an efficient and environmentally friendly technology,electrocatalytic technology is used in various fields such as environmental remediation,hydrogen production,oxygen production and carbon dioxide reduction.However,it needs to further develop the high-efficiency and low-cost electrocatalysts.Metal-organic framework compounds（MOFs）with high porosity,large surface area and adjustable coordination structure are considered as catalytic materials with great potential.In this paper,the vapor deposition method was used to synthesize bimetallic organic framework compounds in situ on the three-dimensional nickel foam substrate.And using defect engineering and doping strategies to design a dual-functional catalyst with both reduction performance and oxidation performance.Then a series of characterization methods were used to evaluate the electrocatalytic performance of the prepared catalyst.The main contents are as follows:（1）The CoNi-MOFs electrode was modified with water plasma to prepare a multi-active-site Co Ni-MOFs-DBD electrode rich in defects.The morphology,element composition and crystallization of Co Ni-MOFs-DBD were characterized and analyzed,and the electrocatalytic performance of the Co Ni-MOFs-DBD electrode for water splitting was investigated under alkaline conditions.The results show that the crystal type of Co Ni-MOFs-DBD after plasma treatment has not changed,the morphology is split from the original large hexagonal structure to a uniform rhomboid structure,and the particle size is changed from the original 10μm to 400 nm.XPS characterization results show that plasma treatment introduces a large number of oxygen vacancies and metal defects,which makes the material have better hydrophilicity（the infiltration angle after treatment is almost 0°,and the untreated one is 122.49°）.Electrochemical test results show that the Co Ni-MOFs-DBD electrode treated with plasma for 2 min has the best catalytic activity,its electrochemical active surface area is 11.7 times that of the untreated electrode,and the current density reaches 10 mA in a 1 M KOH solution·cm^-2,the hydrogen evolution overpotential is 203 m V,and the oxygen evolution overpotential is only 53 m V.When the two-electrode system assembled with this electrode as the cathode and anode is used for the electrocatalytic water splitting experiment,the electric potential required to reach a current density of 10 m A·cm^-2 is only 1.42 V,which is much smaller than that of Co Ni-MOFs without plasma treatment（2.03 V）.（2）The reaction medium water in the plasma modification process was replaced with S-g-C₃N₄ suspension,and the S-g-C₃N₄ doped bifunctional Co Ni-MOFs/S-g-C₃N₄composite electrode was successfully prepared.The SEM image showed that the filamentous structure of S-g-C₃N₄ was wrapped around the periphery of Co Ni-MOFs.XRD and XPS further confirmed the successful loading of S-g-C₃N₄.The electrochemical test results show that the electrochemical active surface area of the Co Ni-MOFs/S-g-C₃N₄electrode is 60.11 times that of the original Co Ni-MOFs and 5.12 times that of Co Ni-MOFs-DBD-2 min.In 1 M KOH solution,the hydrogen evolution overpotential when the current density reaches 10 m A·cm^-2 is 162.6 m V,and the oxygen evolution overpotential is only 5.4 m V.In addition,the electrode has more excellent wastewater purification ability.Under the same reaction conditions,the reaction rate of Co Ni-MOFs/S-g-C₃N₄ electrode to remove phenol is 3.97 times that of Co Ni-MOFs.What’s more,Co Ni-MOFs/S-g-C₃N₄ electrode has high removal efficiency（more than88%）for phenol-containing wastewater with different p H levels,and can maintain good degradation stability.