Synthesis Of Noble Metal Nanocomposites And Their Photoelectrochemical Properties

This thesis mainly synthesizes noble metal nanocomposites,successfully prepares a variety of noble metal nanocomposites such as noble metal heterostructure,noble metal alloy and noble metal/semiconductor heterostructure,and studies the influence of the morphology and structure of the material on its photoelectrochemical properties.The specific research content is as follows:1.Synthesis of noble metal heterostructures and study on the properties of photo-assisted electrocatalytic hydrogen evolution under visible-near infrared lightPtPd modified multi-branched Au@Ag nanocrystal(PtPd-M_Au@Ag)heterostructure was synthesized,the growth mechanism of the heterostructure was explored,and it is applied to the electrocatalytic splitting of water for hydrogen evolution under visible-near infrared light(vis-NIR).Three different heterostructures of CPtPdMAu@Ag,EPtPd MAu@Ag,and TPtPd MAu@Ag were synthesized by controlling the growth positions of PtPd alloy nanoparticles on M_Au@Ag by seed growth method and chemical reduction method.The distribution position of PtPd optimizes the performance of the heterojunction.Among them,C_PtPdM_Au@Ag exhibits excellent photo-assisted electrocatalytic activity.The initial overpotential under vis-NIR is 33 mV,the Tatel slope is 101 mV/dec,and the overpotential is 150 mV at 10 mA cm^-2.The increase in catalyst activity is mainly due to the formation of heterojunctions,and the adjustment of the morphology also helps to increase the electrocatalytic activity(structure effect);because the catalyst has a localized surface plasmon resonance effect,vis-NIR light can effectively excite electrons from the ground state to the excited state,realizing the effective separation of electron-hole pairs(electron effect);Au nanostructures can absorb near-infrared light to generate heat,thereby increasing the temperature of the catalyst(photothermal effect).Structural effect,electron effect and photothermal effect make the catalyst have excellent photo-assisted electrocatalytic activity and improve the electrocatalytic properties of the catalyst.2.Synthesis of noble metal alloys and study on the properties of photo-assisted electrocatalytic hydrogen evolution and methanol oxidation under visible lightThe formation of the alloy structure enables strong interactions between different metal components,thereby improving catalytic activity.In this work,we synthesized self-assembled binary alloys(PtCoand PtCu)and ternary alloys(PtCoCu)using a simple one-pot method.This special alloy nanoparticle not only enhances the hydrogen evolution ability and methanol catalytic oxidation ability in the electrocatalytic process through alloy effect and electron effect,but also improves the utilization rate of visible light and has photo-assisted electrocatalytic ability.In the process of electrocatalytic hydrogen production,the initial overpotential of the PtCoCu alloy under visible light is 14 mV,the overpotential under the current of 10 mA cm^-1 is44 mV,and the Tatel slope is 28.8 mV/dec.After 1000 cycles,the hydrogen evolution reaction activity remained basically stable,and the current density basically did not decay under the12-hour acidic condition test.In the process of methanol oxidation reaction,the current density of PtCoCu alloy under visible light at a potential of 0.7 V is up to 4.2 mA cm^-1.The main reason why PtCoCu can produce excellent performance under visible light is that the Cu element with local surface plasmon resonance(LSPR)effect produces electron effect in the alloy,so that the alloy can effectively transfer electrons under light excitation.Noble metal-based alloys improved the electrocatalytic properties of the catalyst.3.Synthesis of noble metal/semiconductor heterostructures and study on the properties of photocatalytic hydrogen productionTiO₂(B)/CdS/Au and TiO₂(B)/Au/CdS heterostructures were successfully synthesized to investigate the effect of the selected deposition of CdS and Au nanoparticles on H₂ generation.TiO₂(B)spheres(phase B TiO₂)consisted of nanosheets were synthesized via a hydrothermal reaction.The deposition of CdS and Au NPs were carried out using wet-chemical method and a reduction reaction,respectively.The size and amount of Au and CdS nanoparticles were adjusted to optimize the resulting properties and discuss the change of band gap.Two kinds of heterogeneous revealed different photocatalytic hydrogen generation which indicated the position of Au nanoparticles affect the transfer of photogenerated carriers.The hydrogen production rate of TiO₂(B)/CdS/Au heterostructures reached up to 12100?mol g^-1 h^-1,which is about 3.8 times of that of pure TiO₂(B)spheres.This is ascribed to the structure of heterostructures.CdS nanoparticles increase the separation of photogenerated electrons and Au nanoparticles accelerated the transfer of the electrons.The controlled synthesis of noble metal Au,semiconductor TiO₂(B)and CdS successfully improved the photocatalytic properties of the catalyst.