Study Of Selective Reduction Reaction On Noble Metal Chalcogenide Nanomaterials

In the past years,the conversion of small molecules(such as O2,N2,etc)has been received many research interests,since it can effectctively gengeate highly value-added chemicals(H2O2,NH3,etc)through electric/thermal/photocatalysis and other methods.So far,the main challenges of these reactions are low efficiency and selectivity.Therefore,designing and preparing a catalyst with excellent activity and selectivity to achieve the efficient conversion of small molecules is of fundamental research significance and practical application value.Noble metal catalysts have been reported as the promising electrocatalyst,which can solve the problem of low conversion efficiency of small molecules due to the excellent activity.Thus,it is one of the important strategies to develop a highly selective reduction reaction catalyst for the modification of noble metal materials.Noble metal chalcogenide nanomaterials can be formed with surface modified by chalcogens.Such materials have unique surface structures and local environments,which can adjust the structure of the active site,thereby improving the catalytic selectivity of the reaction.In this thesis,by adjusting the structure of the material,we explore the selectivity and activity of the material on the conversion of small molecules,and Pd-Se,Pd-S and Rh-Se nanomaterials with special and dispersed structures were synthesised,respectively,for selective reduction reaction of oxygen,and nitrogen.The main contents are as follows:Chapter 1.The first chapter briefly summarizes selective reduction reaction mechanism of O2 and N2,and catalyst design and ideas for improving performance,further clarifies the basis and research content of this paper.Chapter 2:A uniformly dispersed Pd-Se nanoparticles(NPs)was synthesized by wet chemical method,and the special structure of the material was explored through some characterization methods.Due to the existence of isolated Pd atoms,it can selectively reduce oxygen to hydrogen peroxide(H2O2)under pH-universal conditions(pH=1-13),and has excellent activity and stability.Chapter 3.Based on the mechanism research in Chapter 2,further exploration was carried out,and Pd-S nanocrystals(NCs)with the same special structure were successfully synthesized.The Pd-S NPs crystallize in a tetragonal symmetry.The projected unit cell is composed of two non-equivalent Pd-S metallic bonds.Thus,the material also has isolated Pd atoms.This special structure can enhance the adsorption and activation of O2,which exhibit excellent selectivity,catalytic activity and stability for oxygen thermocatalytic,electrochemical and photochemical reduction.Chapter 4.Through a simple metal surface chalcogenization strategy,Rh-Se nanocrystals with core-shell structure were synthesized.The materials can selectively reduce nitrogen to ammonia,and has excellent activity.In addition,this surface modification strategy is also very versatile,where surface sulfurization,selenization or telluride all can enhance the nitrogen reduction performance of various metal NCs.