Preparation And Performance Of Porous Iron Phosphide And Cobalt Phosphide Electrocatalysts For Hydrogen Evolution Reaction

As the energy crisis and environmental pollution become increasingly serious,the development of efficient,clean and sustainable energy sources has become the focus of current research.Hydrogen,as a high energy density and clean renewable energy carrier,has become the most promising alternative to fossil energy.Among the various hydrogen production technologies,water splitting is the most efficient and environmentally friendly way to produce hydrogen.In water electrolysis process,hydrogen evolution reaction?HER?occurs at the cathode with the assistance of high active catalysts to produce high purity hydrogen.Due to its low overpotential and rapid reaction kinetics,Pt-based noble metals are the most active HER catalysts.However,the high price of Pt-based noble metals greatly limits the large-scale application of hydrogen production by water splitting.Therefore,the search for efficient and cheap non-noble metal HER catalysts has become the hot topic of current research.Due to the low cost and high intrinsic electrocatalytic activity,transition metal phosphides?TMPs?have become typical representatives of non-noble metal electrocatalysts.The thesis aims to enhance the catalytic performance of TMPs by increasing the number of exposed active sites and improving the conductivity of the catalysts.Three-dimensional macroporous iron phosphide self-supported electrode and mesoporous cobalt phosphide self-supported electrode were constructed as high-efficient HER catalysts for water splitting based on the controllable preparation of nanoporous structure.The specific research contents of this thesis include:Firstly,a three-dimensional ordered macroporous iron phosphide self-supported structure?3DOM-FeP/CC?was constructed on the carbon cloth through methods of self-sacrificial templates and low-temperature phosphidation.3DOM-FeP/CC has an interconnected macroporous channels with a pore size ranging from 100 nm to 300nm and a pore wall thickness of approximately 50 nm.The obtained 3DOM-FeP/CC electrode combined the advantages of highly conductive substrate and ordered macroporous structure.Three-dimensional ordered maroporous structure has a large number of available active sites,rapid electron transfer and abundant mass transport channels.At the same time,the conductive substrate can greatly enhance the conductivity of the supported electrode.Therefore,the 3DOM-FeP/CC self-supported electrode exhibited excellent HER performance and long-term stability under acidic conditions,achieving a current density of 10 mA cm^-2 and 50 mA cm^-2 at overpotentials of 68 mV and 158 mV,and the Tafel slope is 42 mV dec^-1.In addition,we prepared meso-CoP/CC?meso-CoP/CC?self-supported electrode and researched its catalytic performance for HER.The mesopores were constructed in the cobalt precursor by using ZnCl₂ as the salt templates,and then the meso-CoP/CC was obtained by low-temperature phosphidation.The meso-CoP/CC was composed of mesoporous pores of 2²2 nm with the specific surface area of 38.65 m²/g.The synthesized meso-CoP/CC catalyst has not only large specific surface area of mesoporous structure,but also high conductivity of conductive substrate.The meso-CoP/CC can fully exert the electrochemical synergy of transition metal phosphide,mesoporous structure and conductive carbon substrate.Therefore,meso-CoP/CC showed high hydrogen evolution catalytic activity and good electrochemical stability.It exhibited overpotentials at 10 mA cm^-2 current density of102 and 118 mV with small Tafel slopes of 55 and 74 mV dec^-1 in acidic and alkaline electrolyte,respectively.