Preparation Of Zr-MOF/Ni-Based Composites For Electrocatalytic Hydrogen Evolution

The use of fossil fuels has caused serious social and environmental problems,and in order to develop a green home,the researchers are very interested in developing new clean energy sources.Hydrogen energy（H₂）is considered as a promising,low-carbon and economical energy source.Electrocatalytic hydrogen evolution is a low-cost and efficient method,and its slow reaction kinetics needs to be overcome with highly efficient electrocatalysts.Traditional noble metals are effective catalysts for low Gibbs free energy in hydrogen evolution reaction（HER）.However,the high cost limits their industrial applications.Therefore,it is urgent to develop new low-cost materials.Among several transition metals,nickel（Ni）-based material is regarded as a promising electrocatalytic hydrogen evolution material,and nickel is the most abundant and favorable catalyst on earth due to its ideal electrochemical activity in alkaline electrolyte solution.Compared with noble metals such as Pt,Ru,and Ir,nickel-based electrode materials,including oxides,phosphide,sulfide,and selenide,have been widely explored for water splitting.However,in practical applications,there are still some disadvantages of low electron transmission rate,poor stability and slow reaction kinetics.The traditional powdered nickel-based material as a catalyst is prone to agglomeration in the reaction process.In order to improve the above defects of nickel-based materials,this study used nickel foam as the substrate to explore different nickel-based derivatives and Zr-MOF to build layered electrocatalytic materials to modify nickel-based derivatives,including improving the stability of materials,improving the electrical conductivity of materials,so as to obtain more promising hydrogen evolution materials.The main research results includes the following several contents.1.Zr-MOF was prepared on Ni foam by hydrothermal method,and Zr-MOF/Ni₃N@NF was obtained by high temperature nitriding.Optimizing the performance of Zr-MOF/Ni₃N@NF by regulating different crystallization temperatures.The results show that the layered composite Zr-MOF/Ni₃N@NF-450 sintered with a high temperature condition of 450℃showed excellent electrocatalytic performance in different p H electrolyte environments.It required 247 m V and 284 m V for Ni₃ N to reach 10 m A cm-2at acid and alkaline conditions,respectively.While under the same conditions,Zr-MOF/Ni₃N@NF-450 only needed 227 m V and 189 m V,and its electrocatalytic performance of the material was improved to a certain extent.The excellent electrocatalytic hydrogen evolution performance of the layered electrocatalyst Zr-MOF/Ni₃N@NF is attributed to the following factors:（i）as a self-supporting electrode,the large pores of nickel foam can be beneficial to the hydrogen precipitation,avoid the material in the process of reaction,（ii）the octahedral morphology of Zr-MOF can effectively improve the electrocatalytic active area,（iii）Ni-N coordination can adjust the hydrogen and hydroxyl binding energy,（iiii）charge transfer between Ni₃ N and Ni interface electronic interaction can affect the reaction of Gibbs free energy.2.The Zr-MOF was first prepared on the nickel foam by hydrothermal method,and then the Zr-MOF/Ni₂P@NF electrocatalytic hydrogen evolution material was obtained by high-temperature phosphating.Optimizing the performance of Zr-MOF/Ni₂P@NF by regulating different crystallization temperatures.The results show that the layered electrocatalytic material obtained by Zr-MOF and Ni₂ P sintered with a high temperature condition of 350 ℃ has the best performance.It required 165 m V and 140 m V for Zr-MOF/Ni₂P@NF-350 to reach 10 m A cm-2 at acid or alkaline conditions,respectively.The excellent electrocatalytic hydrogen evolution performance of Zr-MOF/Ni₂P@NF is attributed to the following factors:（i）Ni₂P exhibits high electrocatalytic activity due to its good electronic structure and hydrogenase-like catalytic mechanism,（ii） the nickel foam as the self-support electrode improves the electronic transmission performance,（iii）the combination of Ni₂ P and the zirconium fund framework makes the internal electron redistribute and optimize the internal electronic structure.3.Zr-MOF was first prepared on nickel foam by hydrothermal method,and then Zr-MOF/NiS₂@NF electrocatalytic hydrogen evolution material with layered structure was obtained by high temperature sulfolation.Optimizing the performance of Zr-MOF/NiS₂@NF by regulating different crystallization temperatures.Zr-MOF/NiS₂@NF-350 obtained at 350℃ shows good electrocatalytic hydrogen evolution performance and excellent stability in the electrolyte environment with different p H values.Only 72 m V is required to reach a 10 m A cm-2 current density under alkaline conditions.The excellent electrocatalytic performance of Zr-MOF/NiS₂@NF is attributed to the following factors:（i）NiS₂,as a typical transition metal sulfide,has low hydrogen adsorption bond energy and high hydrogen hydrolysis rate.（ii）NiS₂ is combined with the zirconium organic framework,and the specific surface area increases the electrochemical active site accordingly,and（iii）the presence of Zr-MOF effectively improves the stability of the material in the acid electrolyte.