Controllable Preparation Of Pd Catalyst And Their Electric Catalytic Methanol Oxidation Behavior Research

The endowment of China’s energy structure is"poor in oil,less in gas,and relatively rich in coal".Coal methanol has become the main production process for Chinese methanol.Currently,the output of methanol exceeds 90 million tons,with over80%coming from the coal-to-methanol route.Under the background of double carbon emissions reduction targets,developing low-carbon utilization technology for methanol is an urgent issue to be addressed in the field of energy chemical industry.Direct Methanol Fuel Cells（DMFCs）use liquid methanol as fuel to convert chemical energy into electrical energy.DMFCs have advantages such as high conversion efficiency,low cost,convenient storage and transportation,high safety,and minimal environmental pollution.In recent years,methanol has become a new favorite in the field of energy.Unfortunately,in practical applications,the Methanol Oxidation Reaction（MOR）occurring in DMFCs’anode is limited by slow kinetic processes and high reaction energy barriers.This greatly affects the energy conversion efficiency of DMFCs.The fundamental reason for this lies in the poor electrochemical performance of DMFCs’anode MOR catalyst.Currently,Pt catalyst is the most commonly used electrocatalytic MOR catalyst.However,the high cost,poor stability,and susceptibility to poisoning under alkaline conditions limit the commercial development of Pt catalysts.Palladium（Pd）,a homologous element of Pt with similar electronic structure and chemical properties,exhibits high activity and stability for MOR under alkaline conditions.To address the issues of catalyst cost and stability,this paper focuses on Pd as the main active metal and studies the essential relationship between the structure of Pd catalyst and its electrocatalytic MOR behavior from three aspects:crystal plane regulation,Pd-Cu alloying construction,and interaction between metal and support.The main research contents are as follows:（1）Controllable adjustment of Pd catalyst and its effect on the performance of electrocatalytic MORA series of Pd catalysts with different proportions of Pd crystal surface were prepared using multi-walled carbon nanotubes（MWCNTs）as a support by employing the ethylene glycol hydrothermal reduction method and adding KBr as a structure-oriented reagent.The microstructure of the Pd catalysts was analyzed by XRD,TEM,and other characterization techniques.The electrocatalytic MOR performance of the Pd catalysts was evaluated using a three-electrode system.The results showed that the catalyst containing a higher proportion of Pd（111）crystal plane exhibited better and more stable MOR reactivity.（2）Controllable construction of Pd-Cu alloy catalyst and its effect on the performance of electrocatalytic MORFive kinds of Pd_xCu_y/XC-72 nano-alloy catalysts with different alloy proportions were synthesized by the hydrazine hydrate rapid reduction method using XC-72 carbon black as support,and changing the catalyst loads.The microstructure and electronic properties were studied using XRD,XPS,and TEM.The results showed that Pd3Cu2/XC-72 has an excellent electronic structure,and its MOR activity is 3.12 times higher than that of commercial Pd/C catalysts.As an anode electrocatalyst for alkaline DMFCs,Pd_xCu_y/XC-72 has the advantages of simple synthesis,good activity and long-term stability,and has broad application prospects.（3）Study on the effect of the interaction between the composite oxide carrier and Pd on the performance of electrocatalytic MORA composite oxide carrier MWCNTs-CeO₂ was synthesized by impregnation and pyrolysis,and the support was used to synthesize an efficient Pd/MWCNTs-CeO₂ MOR catalyst through rapid reduction with hydrazine hydrate.Through a series of characterizations and electrochemical performance studies including XRD,Raman,XPS,and TEM,it was found that Pd/MWCNTs-CeO₂ has a larger ECSA,better electron transport ability and higher stability.Compared with Pd/MWCNTs,it exhibits greater improvement in methanol oxidation activity and stability in alkaline media.The interaction between metal and support leads to the formation of a relatively stable coordination structure between Pd and CeO₂,resulting in more Pd⁰ on the catalyst surface,thereby enhancing its performance.This study presents a new concept for designing high-activity Pd electrocatalysts and demonstrates the great potential of Pd/MWCNTs-CeO₂ as an anode electrocatalyst for direct methanol fuel cells.