Preparation And Performance Research Of Pt-based Catalysts For Electoroxidation Of Small Alcohol Molecules

Global climate change and the continuous reduction of fossil fuel resources have made the development of new alternative energy sources an urgent and important task for modern society.Direct alcohol fuel cells are not limited to the Carnot cycle,and have attracted wide attention from researchers due to their high energy conversion efficiency,portability and operational flexibility using multiple fuels.However,due to the slow anode reaction,the efficiency of the anode reaction,that is,the alcohol oxidation reaction is low,which seriously hinders the wide application of fuel cells.The most important component in a fuel cell is the catalyst.At present,the catalyst is still the precious metal Pt.Although Pt has been widely used as an electrocatalyst for alcohol oxidation,it has suffered some serious problems,including its scarcity,high cost and relatively high cost.Poor operation durability.The main reason for the low efficiency is the weak tolerance of Pt to toxic alcohol oxidation intermediates,especially CO.How to improve the intrinsic activity of Pt and reduce the adsorption of toxic CO substances on Pt is essential for the development of efficient and durable Pt-based catalysts.In order to enhance the anti-poisoning ability of Pt-based catalysts,one strategy is to adjust the electronic structure of Pt by alloying Pt with other metals,thereby weakening the adsorption of CO.Based on the above considerations,in this paper,a simple solvothermal method was selected as the synthesis method to design and synthesize a Pt based nano catalytic material with a specific structure by introducing different metal elements.Introducing Pb to synthesize Pt Pb nano dendrites with 3D structure;introducing Pb and Bi to synthesize Pt Pb Bi hexagonal nanosheets with 2D structure;introducing Sn to synthesize Pt Sn nanowires with 1D structure.The catalytic performance of the above three electro-oxidation catalysts was systematically studied,and three research topics were carried out:（1）Preparation of Pt Pb nano-dendritic catalyst and its performance on methanol electrooxidation:The three prepared Pt₁Pb₁/C,Pt₂Pb₁/C,Pt₃Pb₁/C catalysts were applied to the MOR reaction,and their electrocatalytic performance was systematically studied.Pt₁Pb₁/C is an intermetallic compound with hcp crystal structure.Pt₂Pb₁/C and Pt₃Pb₁/C are alloys with both hcp crystal structure and fcc crystal structure.There is electron transfer between Pt and Pb in the catalyst,and it is the electronic effect between metals that is the fundamental reason for the improvement of catalyst performance.The CV and CA curves show that the Pt₁Pb₁/C catalyst has better catalytic performance and stability,and its mass activity is 2.86 times that of JM Pt/C.What is more prominent is the retention of Pt₁Pb₁/C after 7 hours of CA test.The mass activity is 2.36 times that of JM Pt/C.In addition,the Pt₁Pb₁/C catalyst also showed stronger resistance to CO poisoning.This proves that the material has excellent catalytic activity and stability.（2）Preparation of Pt Pb Bi nanoplate catalyst and its performance on the electrooxidation of C2 alcohol:In the present study,intermetallic Pt Pb Bi hexagonal nanoplates（HNPs）with hexagonal close-packed（hcp）structure has been successfully synthesized via a facile solvothermal synthesis approach.The optimized Pt Pb Bi HNPs exhibits exceptional mass activities in the ethanol oxidation reaction(8870 m A mg_Pt^-1)and the ethylene glycol oxidation reaction(10225 m A mg_Pt^-1)conducted in an alkaline electrolyte,which are 12.7 and 1.85 times higher than those of JM Pt/C,respectively.In particular,the catalytic activity is better than that of most reported Pt-based catalysts.In addition,the optimized Pt Pb Bi HNPs also shows better operational durability than commercial Pt/C.For the ethylene glycol oxidation reaction,its mass activity retained 42.7%even after a chronoamperometric test for 3600 s,which is rare among the reported Pt-based catalysts.By combining X-ray photoelectron spectroscopy and electrochemical characterization,we reveal the electron transfer between Pt,Pb,and Bi;this would lead to weakened CO adsorption and enhanced OH adsorption,thereby promoting the removal of toxic intermediates and ensuring Pt Pb Bi HNPs sample has high activity and excellent stability.（3）Preparation of Pt Sn nanowires and research on its electro-oxidation performance for methanol and ethanol:A Pt Sn nanowire catalyst with an average diameter of 3.95 nm was synthesized by a stepwise method.Synthetic Pt Sn bimetallic nanowires are not Pt Sn alloys,and Sn mainly exists in amorphous form.Through XPS characterization,it is found that Sn on the surface of Pt Sn bimetallic nanowires mainly exists in the form of oxidation state.In the CV and CA tests,Pt₁Sn₁ NWs/C showed better catalytic performance than JM Pt/C.Specifically,in MOR,the mass activity of Pt₁Sn₁ NWs/C(761.5 m A mg_Pt^-1)was JM Pt/C(216.4 m A mg^-1_Pt)3.5 times.In EOR,the mass activity of Pt₁Sn₁ NWs/C is 2.34 times that of JM Pt/C.In addition,in the stability test,Pt₁Sn₁ NWs/C also showed better stability than JM Pt/C.