Preparation Of Two Transition Metal Based Materials And Their Application In Electrocatalytic Hydrogen Evolution

Hydrogen is regarded as one of the most promising sources of clean fuel because of its high energy density,recyclability and zero product pollution.Among them,the production of hydrogen from electrocatalytic water splitting is widely used.In addition,electrochemical supercapacitors take an important position in energy storage by reason of its high reliability,superior power density and cycling stability.The key of achieving high-efficiency electrocatalytic hydrogen evolution reaction and high-performance supercapacitor is electrode materials.Most traditional highly active electrode materials are obtained based on precious metal materials.However,these catalysts can not function efficiently enough due to their expensive and scarcity,which limit their wide application on industry.Therefore,it is important to find the active catalysts which can replace precious metals with low-cost,high-efficiency for energy storage and conversion.Transition metal based materials have emerged as the best candidates to displace noble metal-based electrode materials owing to their abundant reserves,multiple oxidation states and good chemical stability.Recently,transition metal phosphides and transition metal sulfides have shown to have good electrochemical properties.Based on this,two different transition metal compounds were designed and prepared in this thesis,and the performance of hydrogen evolution reactive and supercapacitors were investigated.First,Co_xP/Fe P compounds grown on the surface of nickel foam were prepared by phosphating Cobalt-Iron prussian blue（Co Fe PBA）cubic modified Co（OH）₂nanowires;second,bifunctional Mo-Ni₃S₂ultrathin nanosheets were obtained through the doping of Mo.The details of the study are as follows:（1）Transition metal phosphides are an ideal electrode materials for electrocatalytic hydrogen evolution reaction because of their Pt-like electronic structure,and bimetallic phosphides have better electrocatalytic activity than single metal phosphides.Co_xP/Fe P catalysts were successfully synthesized on nickel foam via hydrothermal and dipping methods followed by heat treatment.The influence of phosphating temperature on the samples were explored under the same other conditions.The elemental composition and valence distribution of Co_xP/Fe P-400 was demonstrated via XRD,XPS,SEM and TEM tests,and the hollow porous cube-on-wire morphology was observed.Electrochemical testings of the obtained composites were performed in alkaline electrolyte.Co_xP/Fe P-400 exhibits a low overpotential of 78 m V when phosphorization temperature is 400 ^oC at 10 m A cm^-2.The test 3000 CV cycles and chronopotentiometry for 12 h are also carried out.（2）Transition metal sulfides have unique charged properties and low-coat,but their are poor of electrical counductivity.To overcome this problem,Mo-Ni₃S₂compound was successfully prepared on nickel foam by continuous hydrothermal means.XRD,XPS,SEM and TEM provide significant information about the chemical composition and structure.Mo-Ni₃S₂,as a catalyst,requires the low overpotential of 65.11 m V and 52.79 m V at 10 m A cm^-2in alkaline and acidic conditions,respectively.Besides,the Mo-Ni₃S₂also displays excellent properties of supercapacitor with the capacitance of 3528 F g^-1at 1.0 A g^-1.The capacitance of Mo-Ni₃S₂remains 96.52%up to 3000 cycling at 3.0 A g^-1.