Study On The Dealloying Of Mesoporous AuTiCe/C Nanocatalysts And Preparation Of SPE Membrane Electrod

In order to achieve the goal of sustainable energy development,hydrogen energy,as a green and renewable new energy,has great potential to replace traditional fossil energy.The preparation and storage of hydrogen energy is the key technology to achieve this goal.The solid polymer electrolyte（SPE）membrane electrode composed of gold（Au）based catalysts can be used for hydrogen production/hydrogen storage integration.The key problem in the current application of Au based alloy catalysts is the development of high efficiency and low cost Au alloy catalysts and the study of the structure-activity relationship affecting the catalytic performance of cyclohexene hydrogenation.In this master’s thesis,AuTi/C and AuTiCe/C alloy catalysts were prepared by ion beam sputtering（IBS）technology.The AuTi/C alloy catalysts were dealloyed by hydrochloric acid（HCl）and perchloric acid（HCl O₄）.SPE film electrodes were prepared by hot pressing process and Nafion film.The hydrocatalytic performance of SPE membrane electrodes was characterized by cyclic voltammetry（CV）,hydrotafel curve and current-timing method（i-t）in a liquid/liquid cyclohexene hydrogenator.After exploring the appropriate range of dealloying corrosion conditions in different acid systems through single factor experiment,combined with the results of orthogonal experiment and range analysis,the optimal treatment parameters of AuTi/C and AuTiCe/C alloy catalysts were determined.Hydrogenation potential,hydrogenation current efficiency and cyclohexane conversion were measured by CV and controlled potential electrolysis Coulomb（BEC）.The effect of electrochemical dealloying method on the catalytic performance of cyclohexene hydrogenation of SPE membrane electrode was investigated.X-ray diffraction（XRD）,transmission electron microscopy（STEM&HRTEM）,X-ray photoelectron spectroscopy（XPS）and specific surface and porosity analyzer（BET）were used to analyze the effects of electrochemical dealloying treatment on the phase composition,surface morphology,crystal structure,surface element valence and hydrogenation activity of the Au-based alloy catalyst.The results indicate that:（1）The optimal dealloying conditions of AuTi/C catalyst in HCl and HCl O₄corrosion systems,namely,the concentration range of corrosion solution is 0.5～1.0 M and 0.2～0.4 M,and the corrosion time range is 30～60 min and 20～40 min,respectively.The temperature range of corrosion liquid is 30～50℃and 50～70℃respectively.（2）The optimal dealloying treatment of AuTi/C and AuTiCe/C catalysts in HCl corrosion system is that the hydrogenation performance of A-5 and C-5 is the best after 45min treatment in 0.75M HCl system at 50℃.In HCl O₄corrosion system,B-4and D-4 were treated at 60℃for 20min by 0.3M HCl O₄ system.After 45min treatment at 50℃in 0.75M HCl system and 20min treatment at 60℃in 0.3M HCl O4 system,the two-step combined electrochemical dealloying treatment of L-B was obtained.The current exchange density（i₀）,electrochemical active specific surface area（ESA）and geometric specific surface area（SSA）were analyzed.It has the best hydrogenation performance.The conversion rates of AuTi/C,A-5,B-4,AuTiCe/C,C-5,D-4 and L-B cyclohexane are 4.89%,7.38%,7.85%,5.81%,10.44%,11.37%and 12.81%,respectively,among which L-B has the highest current exchange density and cyclohexane play conversion rate.The results show that the addition of Ce and the two-step electrochemical dealloying process can also improve the catalytic activity of cyclohexene hydrogenation.（3）In the two-step combined electrochemical dealloying treatment,the XRD peaks of Au and Au₂Ti of L-B are shifted to a large Angle.STEM shows that uniform mesoporous structure and fine nanoparticles appear on the surface of L-B.Au and Ti are mainly the nanoparticles around the pores and in the pores,and Ce is evenly distributed in the boundary of AuTi alloy particles.At the same time,the thin catalyst film surface contains Ti and Ce elements,and the synergism of these two elements can improve the specific surface area and oxygen defect density of the catalyst.High specific area can improve the dispersion of Au nanoparticles.The increase of oxygen defect density can provide more transfer channels for free electrons and increase the concentration of free electrons around Au.The result shows significantly enhanced hydrogenation performance.