Preparation Of Noble Metal-Nonmetal Nanoelectrocatalysts And Their Performance Investigations

Electrocatalysis technology plays an important role in energy conversion（such as fuel cell）and material synthesis（such as electrochemical synthesis of ammonia）,which can greatly reduce our dependence on fossil fuels.At present,the preparation of effective electrocatalyst is a key fact that affects the large-scale application of electrocatalysis.Noble metal catalyst is the most commonly used electrocatalyst because of its excellent catalytic performance,but suffers from high price and scarce reserve,which is not beneficial for commercial application.In order to reduce the cost of noble metal-based catalysts,heteroatom doping is an effective approach to reduce the amount of noble metals and improve the activity and stability of catalysts.In addition,the combination of noble metals with heteroatom-doped carbon materials is also an attractive strategy to reduce the amount of noble metals and improve the performance.These two technologies that combine noble metal elements with nonmetallic elements can induce the unique physical and chemical properties of catalysts,followed by structural design and composition control to obtain excellent nanomaterials with unique morphology,which can significantly improve their electrocatalytic performance.The main research contents and achievements of this thesis are as follows:（1）We report an efficient and universal method for the preparation of unique metal-nonmetal AuPdP nanowires（AuPdP NWs）,in which the Au nanowires（Au NWs）are synthesized by the reaction of chloroauric acid andα-naphthol in a 60°C water bath.Then,AuPdP NWs are synthesized by solvothermal method using Au NWs and tetra（triphenylphosphine）palladium as precursors.Due to the one-dimension nanowire structure and synergistic effect among Au,Pd and P elements,the AuPdP NWs show excellent performance for the electrocatalytic nitrogen reduction to ammonia,with a good NH₃ yield(18.78μg h^-1 mg^-1_cat.),Faraday efficiency（15.44%）and electrochemical stability,which is superior to the pure Au NWs.In addition,this proposed method is a universal strategy for the doing of P and Pd elements into various catalysts,which provides an effective way for the synthesis of high-efficiency electrocatalysts.（2）We report a two-step method for the preparation of amorphous sulfur multilayer decorated gold nanowires（S/Au NWs）.Firstly,Au NWs are synthesized according to above method.Then,sublimated sulfur and Au NWs are mixed in ethanol solution at room temperature to obtain the S/Au NWs.Owing to the one-dimensional structure and chemical adsorption of the sulfur multilayers,the S/Au NWs provide sufficient exposed active sites for the electrocatalytic reduction of nitrogen.During the electrochemical ammonia synthesis,the S/Au NWs possess high NH₃ yield of 21.04μg h^-1 mg^-1_cat.,and the Faraday efficiency of 15.34%.In addition,the S/Au NWs have excellent electrochemical stability due to their one-dimensional nanowire structure.（3）We report to the preparation of N-doped carbon sphere coated monodisperse Pt nanoparticle（Pt@NCSs）with yolk-shell structure by hard template method.Firstly,the silica sphere coated monodisperse Pt nanoparticle（Pt@Si O₂）is used as self-assembly template,where plydopamine as nitrogen and carbon sources is deposited on the surface.After high-temperature carbonization and HF etch,the target product is obtained.The yolk-shell Pt@NCSs compose of ultrathin nitrogen-doped carbon shell and monodisperse Pt nanoparticle core.Due to the unique structure and potential synergistic effect of Pt,N and C elements,Pt@NCSs show excellent catalytic activity and methanol resistance in oxygen reduction reaction.This yolk-shell structure can significantly enhance the catalytic performance and reduce the Pt content,which provides an effective strategy to resolve the high cost and scarce of noble metals.