Study On The Electrocatalytic Oxidation Performance Of Ethanol On Palladium Catalysts Regulated By Heterogeneous/metallic Element Interface

Direct ethanol fuel cell（DEFC）is considered as an efficient and environmentally friendly energy equipment.However,ethanol oxidation reaction（EOR）which occurred on anode is slow and complicated.At present,the commonly used palladium（Pd）-catalysts still have problems such as insufficient activity,susceptibility to be poisoned by intermediate products and poor stability,which limit their commercial development.Therefore,there is an urgent need to develop efficient catalysts with high oxidative removal ability of surface toxic intermediates,as well as high catalytic activity and stability.Numerous studies have shown that the outer electronic cloud density will significantly affect catalytic performance of the active metals for catalytic reactions.According to electronic effect,electron transfer occurs between active metal and support material or other metals.Active metal sites may gain/lose electrons from outside so that their outer electron cloud density may increase/decrease.It is directly related to the adsorption capacity of the reactants and intermediates on the metal sites,and further affecting catalytic performance.The aim of this thesis is to prepare stable and efficient anode catalysts for DEFC,achieving the purpose of improving the catalytic performance through regulating Pdactive sites and optimizing electronic structure by heteroatom and metal elements.The specific contents are as follows:1.Study on the performance of nitrogen/sulfur heteroatom interfacially modulated palladium catalysts for ethanol oxidation reaction.In this work,a nitrogen and sulfur（N and S）co-doped carbon material（Pd@SNC）uniformly loaded with Pdnanoparticles was prepared.It exhibited the best catalytic performance with the mass activity of 945.49 mA·mg _Pd^-1.And the current density remained 84.17%of the first test result after four successive stability tests.The improved performance is mainly attributed to the fact that Pdreceives moderate number of electrons from heteroatom-doped carbon carrier.The d-band center of Pdappropriately lowers.The electronic structure is moderately regulated,which balancing adsorption and desorption capacity of reactants and intermediates.Thus,the energy barrier is relatively lower of overcoming dehydrogenation reaction for EOR.And the toxic CH₃CO^*adsorbed on the surface of Pdcan be removed by oxidation rapidly so that the catalytic activity of Pdcan be restored,exhibiting great catalytic stability.2.Study on the performance of cobalt/zinc metal elements interfacially modulated palladium catalysts for ethanol oxidation reaction.In this work,different cobalt/zinc（Co/Zn）ratio bimetallic ZIF-67 was used as a precursor,followed by absorbing Pd²⁺and low-temperature thermal reduction under H₂atmosphere to obtain Pd-based catalysts with PdCo alloy structure（Pd@n-ZIF-67@CP,n denotes the molar percentage of Co to the total metal）.Electron interactions existed during the formation of PdCo alloy.For Pd@50-ZIF-67@CP,Pdloses the most suitable number of electrons,adjusting Pdelectron structure most moderately.Further,Pd@50-ZIF-67@CP exhibits the best catalytic activity and stability with the specific activity of 66.39 mA·cm^-2.After 4cycles of stability test,it can still maintain 91.3%of the current density after first test.