Synthesis And Electrochemical Research Of Doped Transition Metal Phosphide

Hydrogen is considered as an ideal substitute for fossil fuels due to its high energy and non-polluting properties.The 21 st century is known as the century of hydrogen energy.At the same time,with the commercialization of hydrogen fuel cells,the demand for hydrogen energy is more intense.At present,electrolysis of water is the most ideal way to produce hydrogen.Therefore,it is very important to develop a catalyst with high efficiency of hydrogen evolution reaction.Transition metal phosphides have ignited researchers' enthusiasm due to their unique crystal structure,electrical conductivity and stability.However,compared with precious metals,there is still a big gap to conquer.How to narrow this gap is the main direction and purpose of this paper.This thesis take with the synthesis method of transtion metalphosphide nanomaterials,proposing and optimizing the method for improving the HER activity from optimizing the eletronic structure and changing the morphology of the catalyst.the scheme of improving the hydrogen evolution activity of catalysts is studied by optimizing the electronic structure or changing the morphology of the catalyst.The specific experimental research contents are as follows:1,Nitrogen-doped molybdenum phosphide?N-MoP/N-CNT?supported on nitrogen-doped carbon nanotubes was synthesized in one step by gas phase synthesis using ammonium hypophosphite as both a phosphorus source and a nitrogen source.The thermogravimetric-infrared analysis of ammonium hypophosphite shows that the ammonia is decomposed into phosphine and ammonia respectively under high temperature conditions.Therefore,ammonium hypophosphite can be used as both a phosphorus source and a nitrogen source in the process of phosphating.Nitrogen doping of the product is also achieved,simplifying the synthesis process.XPS analysis showed that the binding energy of Mo was deviated after nitrogen doping,indicating that the doping has an effect on the electronic structure of MoP.Owing to the regulation of single doping,the obtained N-MoP/N-CNT exhibits excellent HER activity,and the corresponding overpotential is only 103 mV at a current density of 10 mA cm^-2.2,The doped phosphide is obtained by one-step pyrolysis of the composite precursor obtained by self-assembly.Melamine contains a large amount of amino groups,however,phosphomolybdic acid,phytic acid and graphene oxide contain a large number of oxygen-containing groups.The condensation reaction between amino groups and carboxyl groups can be obtained by self-assembly process.A complex contain a large amounts of N,P and Mo elements was obtained by the Condensation reaction between amino and carboxyl group.MoP/N,P-rGO was obtained by pyrolyzed in an inert atmosphere.This method avoids the production of PH3 gas.XPS analysis also showed that nitrogen and phosphorus were successfully doped into graphene.Compared with the undoped catalyst,MoP/N,P-rGO exhibits higher HER performance,and the corresponding overpotential is 115 mV at a current density of 10 mA cm 2.3.A new method based on hexachlorotripolyphosphazene and 4,4-dihydroxyphenylsulfone to assist in the synthesis of nitrogen,phosphorus and sulfur co-doped metal phosphide has been developed.An organic layer containing a large amount of nitrogen,phosphorus and sulfur obtained by condensing hexachlorotripolyphosphazene with 4,4-dihydroxyphenylsulfone on the surface of the metal-containing nanomaterial,and then directly calcining in an inert atmosphere to obtain nitrogen and sulfur co-doped metal phosphide.This method has good universality.We have sucessful synthesized nitrogen and sulfur co-doped metal phosphide by use of metal oxide,MOF,carbon-supported oxide and other substrates,indicating that this method is an effective method for synthesis of nitrogen and sulfur co-doped metal phosphide.And nitrogen and sulfur co-doped metal phosphide showed better HER activity.4.y-s H-CoP@H-NiCoP catalytic material having a secondary hollow structure was synthesized.ZIF-67 was used as a template,etched by nickel nitrate solution,and then phosphatized in an inert atmosphere to obtain a y-s H-CoP@H-NiCoP catalyst with a unique secondary hollow structure,which was emerged with hollow nanospheres,and the wall of nanosphere is composed of smaller NiCoP hollow nanoparticles.The catalyst has a large specific surface area,exposing more active sites,and the secondary hollow structure brings better mass transfer effect.It shows excellent HER performance with a current density of 10 mA cm^-2 corresponding to an overpotential of only 105 mV.