Preparation And Electrocatalytic Oxygen Evolution Performances Of NiFe-based Transition Metal Phosphides

Water electrolysis（including freshwater electrolysis and seawater electrolysis）is a clean energy conversion technology.However,the oxygen evolution reaction（OER）severely restricts the energy conversion efficiency of water electrolysis due to its slow dynamics and high overpotential.Using efficient catalysts can reduce the overpotential of OER,thereby improving the efficiency of water electrolysis.At present,noble metal catalysts such as Ru O₂ and Ir O₂ are the most advanced OER catalysts,but their scarcity and high cost limited their large-scale applications.Therefore,it is necessary to design and prepare high-performance non-precious metal OER electrocatalysts.Transition metal phosphides（TMPs）have the potential to replace noble metal catalysts due to their great merits of low price,good electrochemical activity and stability along with facile preparation.Given this,this thesis selected TMPs for investigation.Through the introduction of functional substrates and the construction of self-supporting heterostructures,two types of TMPs-based catalysts were prepared.And,we also respectively measured their electrocatalytic OER performance in freshwater and seawater solutions.The detailed results are listed as follows:1.The Ni Fe Co P nanoparticles were coupled with MXene conductive substrate（Ni Fe Co P/MXene）through hydrothermal growth and low-temperature phosphating strategies.In Ni Fe Co P/MXene,benefiting from the negatively charged groups on the surface of MXene,the Ni Fe Co P nanoparticles were uniformly distributed on the surface of MXene,which improves the exposure of active sites and the transfer of charges.In addition,the highly electronegative Mxene and P species promoted the formation of high-valent metal sites on the catalyst surface,leading to the enhancement of OER intrinsic activity.In the 1 M KOH solution,the Ni Fe Co P/MXene catalyst showed good OER performance,with an overpotential of only 240 m V at 10 m A cm^-2.And,it had superior electrolytic stability over 40 h.2.We prepared self-supporting Fe Mo@Ni₂P/NF heterojunction catalysts on nickel foam（NF）through a hydrothermal-phosphating-solvothermal strategy.In an alkaline seawater solution,Fe Mo@Ni₂P/NF achieved a large current density of 1000 m A cm^-2at an overpotential of 370 m V.What’s more,the Fe Mo@Ni₂P/NF||Fe Mo@Ni₂P/NF pair can be used for overall alkaline seawater electrolysis.And,this two-electrode electrolyzer can drive an industrial-level current density of 500 m A cm^-2 at a voltage of1.91V,which is more valuable for practical applications.Notably,this electrolyzer still can maintain a high catalytic activity during the long-term seawater electrolysis process due to the good stability of the self-supporting electrode and the synergistic effect between the heterojunctions.