Controlled Construction Of Nickel Selenide Composite Catalysts And Their Performance In Electrocatalytic Oxidation Of Methanol And Urea

With the rapid development of industry,energy consumption has increased obviously and environmental pollution has become increasingly serious,so developing new energy devices or finding alternative clean energy sources has become a hot research topic nowadays.Methanol and urea are common organic pollutants in wastewater,but they have the advantages of high energy density,stability and easy transportation,which make methanol and urea not only as fuel for new fuel cell devices,but also assist in the electrolysis of water to produce hydrogen at the cathode.However,the oxidation process of methanol and urea is still constrained by slow kinetics,low catalyst activity and poor durability.To address these problems,this paper designed and synthesized a series of nickel-based catalysts and modified the catalysts to obtain highly active catalysts suitable for methanol oxidation reaction（MOR）and urea oxidation reaction（UOR）,and analyzed the influence of the catalyst synthesis conditions on the catalyst performance.The main research of this paper is as follows:（1）N doped carbon composite nickel selenide（Ni Se/NC）and nickel diselenide（Ni Se₂/NC）catalysts were prepared and investigated for their applications in MOR and UOR:Ni Se/NC and Ni Se₂/NC catalysts were successfully prepared by lyophilization,high temperature calcination and selenization at different temperatures using Na Cl as the template,and the effects of Na Cl template and N doping on the catalyst performance in MOR and UOR reactions were investigated.The test results show that the 3D architecture of Ni Se₂/NC-450 has the best MOR(peak current density up to164.68 m A cm^-2 and potential of 1.33 V at 10 m A cm^-2)and UOR(peak current density up to 136.04 m A cm^-2 and potential of 1.32 V at 10 m A cm^-2)electrochemical properties.The catalysts were stabilized for electrochemical oxidation of methanol up to 10000 s and for urea for more than 10 h.The better performance of Ni Se₂/NC-450 for methanol and urea reactions may be related to the increased electrochemical active area after selenization and enhanced electrical conductivity after N doping with carbon.This study provides a new way to prepare inexpensive transition metal-based catalysts and their use as efficient and stable anodic oxidation electrocatalysts.（2）CeO₂ modified nickel selenide catalysts with N doped carbon were prepared and investigated for their applications in MOR and UOR:CeO₂-Ni Se₂-450-NC,CeO₂-Ni_0.85Se-550-NC and CeO₂-Ni_0.85Se-650-NC catalysts were successfully prepared by salt template method after high temperature calcination and selenization at different temperatures.The effects of Na Cl template and N doping on the performance of the catalysts in the MOR and UOR reactions were investigated.The test results show that the sheet structure of CeO₂-Ni_0.85Se-550-NC has the best electrochemical properties for MOR and UOR.The peak current densities of CeO₂-Ni_0.85Se-550-NC in MOR and UOR are 200.36 m A cm^-2 and 178.56 m A cm^-2,respectively.Meanwhile,the CeO₂-Ni_0.85Se-550-NC requires only 1.31V（MOR）and 1.29 V（UOR）to reach 10 m A cm^-2,respectively.The DFT study indicates that CeO₂-Ni_0.85Se-550-NC has the best reaction path with the synergistic effect of CeO₂ and Ni_0.85Se.In addition,the synergistic interaction between CeO₂ and Ni_0.85Se can generate more defects as catalytic sites,and the N doping into the carbon substrate can accelerate the electron transfer,and these factors lead to the better performance of CeO₂-Ni_0.85Se-550-NC catalyst.This work provides a new strategy for the design of efficient nickel selenide based catalysts for the oxidation of other organic compounds.