Study On The Interfacial Engineering For Electrocatalytic Activity

The rapid development of economy and society results in the fast depletion of natural energy and the deterioration of the environment,it is urgent to develop efficient and green alternative energy.Electrochemical energy storage and conversion has been proven to be an important way to solve these issues.The design and development of efficient electrocatalysts are the hotspots in the field of electrochemical energy conversion.Rational designing and engineering the interfaces are of great significance to the modulation of electrocatalytic reaction,which mainly proceeds at the solid(electrode)/ liquid(electrolyte solution)/ gas(solid / liquid / gas)three-phase interfaces.On the basis of engineering of interfacial property and modulation of electronic structure,we started the thesis by first introducing the appropriate reaction active sites on catalyst surfaces.We investigated the elemental steps of the electrocatalytic hydrogen oxidation reaction.Based on the results,a bifunctional reaction mechanism at atomic level was proposed,which provides a fundamental guidance for improving catalyst performance and catalyst design.On other hand,we explored the interfacial properties dependent electron transfer process between biomolecules and electrode interface,which is beneficial to the construction of high-performance biofuel cells and biosensors.The present Master Degree Thesis focuses on the following three issues:1.Preparation of Ru@Pt core-shell nanostructure for enhancing hydrogen oxidation reaction(HOR).Ru-r GO nanohybrid was prepared by a one-step reduction method using Ru Cl3 as the precursors,graphene oxide(GO)as the carrier,and Na BH4 as the reducing agent.A Cu monolayer was first underpotentially deposited on the surface of the Ru nanoparticles,followed by galvanic displacement reaction using Pt Cl42-to form a Pt monolayer(Ru@Pt core-shell nanoparticles).The hydrogen binding energy of the Ru@Pt core-shell nanoparticles is decreased due to the alloying of Ru metal,leading to a superior electrocatalytic activity toward HOR than commercial Pt/C.This study provides a new idea for designing high-performance metal catalysts.2.Bifunctional mechanism of hydrogen oxidation reaction on atomic level tailored-Ru@Pt core-shell nanoparticles with tunable Pt layers.Underpotential deposition method combined with galvanic replacement technology(UPD-GD)proposed in the previous chapter was used for controlling the spatial distribution of Pt atoms on Ru nanoparticles at atomic scale.The electronic structure and surface properties were modulated and the hydrogen oxidation mechanism was clarified in this chapter.The Pt atomic multilayers on Ru NPs could be obtained by repeating the UPD-GD process.By controlling the number of UPD-GD cycles,precisely tailoring Pt catalysts at atomic level on Ru NPs can be achieved.It is suggested that the electronic interaction between Pt shell and Ru core,combined with lattice effect and steric effect will dramatically influence the HOR catalyst activity.The electrochemical results suggest that the Ru@Pt with double Pt layers shows superior electrocatalytic activity toward HOR owing to the oxophility effect.HOR activity decreases with increasing the thickness of Pt shell.In view of the electronic and oxophility effects of Ru,we propose that HOR at Ru@Pt proceeds via a bifunctional mechanism.Our results provide a fundamental for the design of high-performance HOR catalyst.3.Surface engineering the conformation and orientation of immobilized laccase to enhance the oxygen reduction reaction(ORR).For exploring the influence of interfacial properties on the conformation and orientation and in turn the electrochemical properties of proteins,we tried to control the adsorption orientation of laccase through controlling the surface properties of gold electrode,and realize the direct electron transfer between proteins and electrode to enhance the electrocatalytic oxygen reduction activity.We used laccase and cytochrome c as model molecules to investigate their immobilization and electrochemical properties on electrode surfaces with different wettability and charge properties.Cytochrome c immobilized by the electrostatic incorporation shows efficient electrochemical signal of direct electron transfer.However,due to the large molecular mass of laccase along with its active site totally wrapped by protein layer,the direct electron transfer is not observed at the interface between laccase and the hydrophobic electrode.Our results show that the surface wettability of electrode is crucial to the protein conformation and electrochemical properties.