Studies On The Surface And Interface Control Of Pd-Based Nanomaterials And Their Catalytic Prooerties

With the rapid development of modern society,a large amount of use of non-renewable fossil fuels,on the one thing,will cause serious energy crisis due to its limited reserves;and on the another thing,it will release many harmful substances that they may cause serious environmental pollution.Hence,searching efficient,green and sustainable energy sources is very important.At present,many molecular transformation reactions are becoming research hotspots due to the production of some valuable products,high energy output and green process,such as alcohol oxidation and oxygen reduction reactions in fuel cell,hydrogen evolution and oxygen evolution reactions in water splitting,and hydrogen-oxygen mixed reactions in direct synthesis of hydrogen peroxide.The development of platinum(Pt)-based noble metal nanomaterials,which exhibit excellent catalytic performances in those reactions,is limited due to their high price,poor stability,and easier deactivation.Since palladium(Pd)is akin to Pt and has the comparable catalytic activity than Pt,Pd-based nanomaterials have gradually become a research hotspot and are considered as a promising catalyst for these molecular transformation reactions.A large number of studies have shown that the surface and interface of catalysts play a vital role in catalyzing molecular transformation reactions,since they serve as reaction sites.Therefore,reasonable regulation of the surface and interface of Pd-based noble metal nanocatalysts,including the composition,morphology,structure and defects,will be an effective strategy to boost their catalytic performancesIn this paper,we mainly introduce the synthesis and characterization of Pd-based nanomaterial,and further discuss the catalytic performance of Pd-based nanomaterials in molecular transformation reactions,including PdFePt nanomeshes with different spin concentrations for catalyzing alcohols oxidation reactions,PdCoN nanoparticles with the Pd/CoN interface and regulation of the coverage of CoN on the Pd surface for catalyzing the hydrogen evolution reaction from water splitting,and PdM(M=Fe,Co,Mo,In,ctc.)nanoparticles introduced with different metals for direct synthesis of hydrogen peroxide The main contents are summarized as followsChapter 1.This part briefly summarizes the reaction mechanism and performance evaluation index of alcohol oxidation reaction,hydrogen evolution reaction and direct synthesis of hydrogen peroxide reaction,and further introduces some commonly used control strategies for regulation of surface and interface of catalysts.Finally,the basis and content of this paper are clarifiedChapter 2.A simple solution synthesis method was used to prepare PdFePt alloy with two-dimensional nanomesh structure,and its catalytic performance in alcohol oxidation reaction was studied.The spin concentration of the PdFePt nanomeshes was effectively controlled by adjusting the Fe content,thereby affecting the adsorption of intermediate species OHads.The strong adsorption of OHads is beneficial to oxidizing the adsorbed COads on the surface of Pt to generate CO2 and release Pt sites.This improves the catalytic performance,meanwhile,the poisoning of the catalyst is avoided,thus enhancing the stability.Chapter 3.PdCoN nanoparticles with Pd/CoN interface were prepared by high-temperature calcination of synthesized PdCo nanoparticles in ammonia(NH3)atmosphere,and their catalytic performance in hydrogen production from electrolysis of water was studied.The results indicate that the key to improve the catalytic performance is the construction of Pd/CoN interfaceChapter 4.A universal wet-chemical method was developed to prepare PdM(M=Fe,Co,Mo,In,etc.)nanoparticles with different components and a few nanometers.Catalytic performance in direct synthesis of hydrogen peroxide was studied.The introduction of the second metal has an effect on the electronic structure of Pd,thereby improving the catalytic performance and reaction selectivity of the catalyst.