Design Of NiTe₂-Based Electrocatalyst And Its Performance For Electrolytic Water Splitting

Energy is an important guarantee for human survival and development,and plays a vital role in the development of modern economy and society.With the depletion of fossil energy and human demand for energy,the world gradually turns its research ideas to the development of new energy sources.Hydrogen energy stands out among many new energy sources and has gained widespread attention.Electrolytic water splitting can effectively produce high purity H₂ on a large scale without producing other polluting gases.Water splitting consists of two half-reactions:oxygen evolution reaction（OER）,and hydrogen evolution reaction（HER）.When four electron transfers occur during the reaction process,the higher energy barrier hinders the reaction process and thus the electrolysis of water.Therefore,the search for the perfect electrocatalyst that can improve the efficiency of the reaction and speed up the reaction process,thus reducing the reaction overpotential,is an urgent problem to be solved.At present,in the process of electrolytic water splitting,metallic platinum is an excellent electrocatalyst for hydrogen evolution reaction,while iridium and ruthenium oxides are excellent electrocatalysts for oxygen evolution reaction,but due to the expensive and low content of precious metals,they are not suitable for mining and have poor stability,which limits the industrial mass production,so the development of non-metallic electrocatalysts with high crustal content,low cost and high efficiency to replace the traditional precious metal catalysts is imperative.Nickel is very high in the earth’s crust,and the development of nickel-based electrocatalysts is the primary choice and has long-term relevance based on cost and practicality considerations.Nickel-based transition metal electrocatalysts have received much attention from researchers because of their simple synthesis method and good electrocatalytic performance.In particular,the low electronegativity values and soft base characteristics of telluride electrocatalysts are the key to improve the electrocatalytic performance,and these tellurides also have the characteristics of electron cloud leaving domains,resulting in solids with excellent properties of enhanced charge mobility and high electrical conductivity.In this thesis,NiTe₂-based electrocatalysts were synthesized on nickel foam（NF）using different strategies to enhance the catalytic activity of OER and HER through modulation,and the main research works are as follows.（1）S-NiFe₂O₄/NiTe₂ was synthesized by a two-step hydrothermal method and air-fired in a tube furnace,and the nanosheet morphology of the electrocatalysts was refined,which exhibited excellent OER catalytic performance,requiring only 210 mV overpotential to be provided at a current density of 10 mA cm^-2,significantly lower than that of the undoped NiFe₂O₄/NiTe₂,and single-component catalysts.At the same time,it also had a long-term stability,which was stabilized for 33 h at a certain current density in 1 M KOH solution,and more importantly,the morphological test results after testing the simultaneous stability also remained basically the same as when it was not tested,both of which proved its good stability.（2）Preparation of Fe-NiTe₂/Ni₂P 3D nanoparticles with better electrocatalytic activity and excellent stability due to the simple doping of Fe atoms.The OER activity of Fe-NiTe₂/Ni₂P required only 190 mV overpotential at a current density of 10 mA cm^-2.Moreover,the complex interweaving of nanoparticles made the catalyst constitute a porous structure with a large number of exposed active sites and sufficient channels for oxygen release and mass exchange.In addition,the doping of Fe improves the electronic structure of the catalyst,accelerates the electron transfer and increases the activity of the catalyst.The catalyst remained stable in 1M KOH solution for 22 h,indicating its strong corrosion resistance.（3）N-Fe₂O₃/NiTe₂ was prepared by a simple one-step hydrothermal and tube furnace nitriding method.The doping of N atoms,the combined interaction of Fe₂O₃ and NiTe₂ of this catalyst resulted in the alteration of the electronic structure of the catalyst,which was more favorable to improve the OER and HER catalytic activities.The HER overpotential of N-Fe₂O₃/NiTe₂at a current density of 10 mA cm^-2was only 70 mV and remained stable for 13 h.The doping of N atoms and the combined interaction of Fe₂O₃ and NiTe₂resulted in the alteration of the electronic structure of the catalyst,which was more favorable for the improvement of OER and HER catalytic activities.Due to the good OER and HER performance of the catalyst,we also prepared a bipolar system,which fortunately required only 1.54 V overpotential at 10 mA cm^-2for the overall water cleavage and remained stable for 42 h.All of these confirmed that N-Fe₂O₃/NiTe₂ was an excellent bifunctional electrocatalyst.