Preparation And Electrocatalytic Performance Of Pt Support On MOFs Derived Carbon Catalyst For Methanol Electrooxidation

Methanol electrooxidation reaction（MOR）is extremely important to achieve high-efficiency energy conversion of coal-based methanol.It can not only use in direct methanol fuel cell（DMFC）but also can be applied to the electrolysis of methanol to hydrogen.Some of the major problems with the process of electrocatalytic oxidation of methanol can be documented as follows:the high cost of Pt-based catalysts,poor stability,and poisoning originated by the adsorption of CO-like intermediates in the dehydrogenation process of methanol on catalysts,reducing the efficiency of methanol oxidation.Enhancing the anti-poisoning ability of Pt-based catalysts is the key to developing high-efficiency MOR catalysts.In this thesis,Fe,N,Sn,and other elements are introduced into carbon-based materials derived from metal-organic frameworks（MOFs）to regulate the interaction between Pt and the support,and design platinum-based electrocatalysts with high MOR electrocatalytic activity.Using the metal-organic framework（MIL-100）as the self-sacrificial templates,a carbon material with a high specific surface area was successfully synthesized,which is conducive to obtain highly dispersed Pt nanoparticles（NPs）proved by the characterization test.At the same time,there is a strong interaction between the Fe/Fe₃C species on the carrier and Pt NPs,and the electrons of the Fe species migrate to Pt.This electronic effect weakened the chemisorption strength between Pt and intermediate CO,enhancing the resistance to CO poisoning ability of the catalyst.For MOR,the prepared catalyst（Pt/Fe-PC-700）exhibits excellent mass activity of 745m A mg^-1_Ptin acidic medium,which is 3.03 times of commercial Pt/C(246 m A mg_Pt^-1).To further improve the stability of the catalyst,a nitrogen-doped carbon composite material（Fe-N-PC）was prepared by a simple method and used as a catalyst carrier.It was found that the introduction of N can effectively increase the degree of graphitization of carbon materials,and promote the dispersion and anchor of Pt NPs,which is conducive to obtain Pt NPs with smaller size and more uniform distribution,improved the MOR activity,stability,and CO tolerance.For MOR,the mass activity of Pt/Fe-N-PC-700 in acidic medium is 844 m A mg_Pt^-1,which is 1.13times of Pt/Fe-PC-700 catalyst(745 m A mg_Pt^-1),and the stability of Pt/Fe-N-PC-700catalyst is improved and the stability of Pt/Fe-PC-700 catalyst（500 turn CV test）is improved by 26.88%.Pt-based catalysts can not only improve the anti-poisoning ability by changing the adsorption strength of Pt and CO through electronic effects but also accelerate CO oxidation and promote CO desorption from the Pt surface by providing active oxygen-containing species(OH_ads).The Pt-based catalyst was modified by adding Sn,an oxyphilic metal:On the one hand,the Pt/Sn O₂-PC catalyst was successfully prepared by adding Sn O₂,and the effect of the mass ratio of Sn O₂to PC on the performance of the catalyst was studied.The presence of Sn O₂not only improved the stability of the catalyst but also promoted the oxidation of CO-like intermediates adsorbed on the adjacent Pt surface by OH_adsspecies,which improved the anti-poisoning ability of the catalyst.When the mass ratio of Sn O₂to PC is 5/15,the catalyst has the best performance.The mass activity of MOR is 727 m A mg_Pt^-1,which is 2.95 times the commercial Pt/C catalyst(246 m A mg_Pt^-1).It can effectively avoid the dissolution of active metal Pt,thereby improving the catalytic stability of the material.Another strategy is to introduce metal Sn and Pt to form an intermetallic compound to prepare Pt Sn/PC catalyst.When the atomic ratio of the two is 1/2,the MOR mass activity of the catalyst in an acidic medium reaches 678 m A mg_Pt^-1.After500 rounds of CV test,the activity is only reduced by 7.45%.