Study On The Pt-Zn System And Its Electrocatalytic Oxygen-Related Performance Based On Size And Support Effect

Ozone（O₃）is a green and environmentally friendly strong oxygen agent,which can effectively kill microorganisms such as viruses and bacteria,and can quickly oxidize and decompose organic substances.It is widely used in water treatment and air purification.As the most promising ozone-generating process,the production of ozone by electrolyzed water has advantages,such as simple equipment,small size,and convenient movement.As a good catalyst for the electrocatalytic production ozone,platinum has aroused the research interest of researchers.Therefore,a series of different sizes platinum-zinc alloy catalysts supported on zinc single atom nitrogen-doped carbon support（the size of alloy:2.2 nm、3.7 nm、4.5 nm、7.7 nm and12.9 nm）were designed and synthesized in this thesis,and their electrochemical properties and their reaction mechanism were studied in depth.The research results show that the catalyst in this research system exhibits size and synergistic effect on the electrocatalytic preparation of ozone,and achieves the best catalytic effect when the platinum-zinc alloy size is 7.7 nm,and realize 4.2%faraday efficiency at a current density of 50 m A/cm².In addition,this thesis also studies the oxygen reduction performance of the catalysis,the best catalytic effect is achieved when the size of platinum zinc alloy is 3.7 nm.Its half-wave potential is 0.774 V vs.RHE,which is comparable to 0.786 V vs.RHE for commercial Pt/C.In the life and methanol anti-toxicity test,it shows super stability and anti-toxicity,and it shows excellent electrocatalytic activity,stability and super anti-toxicity shell due to its size and single atom support effect.（1）The preparation of platinum-zinc catalysts with different sizes.Platinum nanoparticles with different sizes were firstly prepared by an alcohol reduction method,and then they were mixed with dimethylimidazole and zinc nitrate hexahydrate in methanol solution.Then the ZIF-8 embed with platinum nanoparticles was obtained.The surface of Pt@ZIF-8 was modified by tannic acid to form Pt@ZIF-8@TA.Due to the migration of zinc atoms during calcination,a series of platinum-zinc nanoparticles with different sizes are finally formed.In addition,for the strong interaction between tannic acid and ZIF-8,it forms a concave octahedron with a large surface area.The obtained X-Pt Zn/Zn-N-C catalysts were used in EOP and ORR reactions.（2）The research of EOP performance.Among the catalysis of X-Pt Zn/Zn-N-C,the 7.7-Pt Zn/Zn-N-C has the best electrocatalytic performance in ozone production and exhibits structurally sensitive characteristics.In addition,Pt/Zn-N-C and Pt Zn/XC-72 as comparison samples were also prepared and tested.Their catalytic activity was much lower than that of 7.7-Pt Zn/Zn-N-C.The results show that the existence of synergistic effects between zinc single atom and nanoparticles.Theoretical calculation further confirmed that:1.the proportion of the crystal plane structure changes with different sizes,2.the different crystal planes play different roles in the reaction process,3.there are synergistic effects between the zinc single atom and the nanoparticles,the effects greatly enhances the catalytic reaction activities.（3）The research ORR performance.Among the catalysis of X-Pt Zn/Zn-N-C,3.7-Pt Zn/Zn-N-C has the best electrocatalytic performance in oxygen reduction,and exhibits superior electrocatalytic activity over commercial Pt/C.In addition,after55-hour i-t and 3000-cycle C-V lifetime,it still shows excellent electrocatalytic activities.In the methanol toxicity test,3.7-Pt Zn/Zn-N-C showed superb tolerance,and the number of electron transfer during the electrocatalytic oxygen reduction process was four.