Study On Active Phase And Microkinetics Of PtRu-based Catalysts In Alkaline Hydrogenation Reaction

In recent years,clean energy and hydrogen energy conversion devices represented by hydrogen energy and alkaline membrane fuel cells have attracted much attention.However,even in the presence of noble metal-based catalysts,the anodic oxidation reaction(HOR)rate in this battery is still slow,which severely restricts its commercialization.Therefore,it is of great significance for the development of fuel cells to study the reasons for the slow reaction of HOR in an alkaline environment.In this thesis,based on density functional theory,through potentiostatic calculation,kinetic analysis and other research methods,the factors such as surface H atom pre-adsorption and oxidative reconfiguration were investigated,and the reasons for the slow reaction of Pt catalysts and the reasons for the slow reaction of PtRu-based catalysts in alkaline HOR were revealed.The reactive phase of the catalyst,the main contents are as follows:1.The surface pre-adsorption of Pt(111)was explored by the adsorption isotherm and kinetic equation,and the surface H pre-adsorption coverage tended to be 1 ML and maintained a dynamic equilibrium by using the structural stability and self-consistent iteration of coverage as evaluation indicators.The rate control degree of HOR reaction kinetics was analyzed,indicating that the basic HOR rate control step is Volmer reaction with OH＿*as the basic intermediate,and more importantly,the metastable intermediate will promote the HOR reaction.And the Tafel-Volmer mechanism is the dominant step for Pt(111)catalyzing alkaline HOR reaction.2.The thermodynamic stability analysis was carried out for Ru whose surface oxidation degree was limited by electrode potential and p H.It was found that Ru(001)surface was more inclined to generate oxides rather than hydroxides,and the stable structure ofθ_O=2 ML was determined.The reconstituted Ru(001)surface does not pre-adsorb H due to the strong oxophilicity of Ru.When calculating the HOR reaction process,it is found that the surface structure of Ru depends heavily on the electrode potential,and the correction result has a large error,so it is not suitable for the HOR kinetic analysis.3.Preliminary exploration from pure metal Pt,Ru to PtRu(111)alloy,calculating the surface energy of different amounts of Ru segregation and O coverage,and found that PtRu alloy only has surface oxidation,and there is no subsurface oxidation.Moreover,the adsorbed 1 ML O atoms after reconstitution will hinder the segregation of Ru atoms,so that the surface stability of this structure is the best at different U and p H values.Due to the introduction of Pt,the pre-adsorption coverage of H on the alloy surface isθ_H≈1 ML and maintains a dynamic equilibrium,and Ru will enhance the adsorption energy of Pt-H in the alloy.This calculation provides theoretical support for further research on Ru-based catalysts.