Pt Alloy Catalyst With Ordered Mesoporous Framework And Study On Methanol Oxidation Performance

Due to the continuous growth of energy demand,the massive consumption of natural resources,and global warming,human society is facing an energy crisis.Methanol has attracted great attention as an alternative fuel in direct methanol fuel cells and is expected to become a future energy conversion resource.However,the slow electrochemical oxidation of methanol hinders its scalable application at a commercial level.Therefore,the improvement of the catalytic performance of methanol oxidation reaction is the key to the development of a new generation of direct methanol fuel cells.Among them,the special morphology design and reasonable composition adjustment of platinum and palladium（Pt Pd）alloys are common strategies to obtain excellent catalytic performance in the methanol oxidation reaction.At the same time,the ordered mesoporous structure shows great catalytic potential due to its high specific surface area,large pore volume,and abundant and adjustable pore diameter.Based on this,this article mainly launched the following two aspects of research work:（1）A simple and universal interfacial assembly method was developed to prepare Pt Pd hollow microspheres with ultra-thin mesoporous shells（Pt Pd-MHS-0.15-0.5）.Using triblock copolymer F127 as soft template,Si O2 microspheres as hard template and TMB as swelling agent,Pt Pd alloy was developed by co-reduction of K2Pt Cl4 and Pd Cl2.At the same time,hollow Pt Pd nanospheres with different shell thickness were obtained by adjusting the content of materials.In the MOR test,the thinner the shell,the better the activity.Due to its good mesoporous structure,large hollow cavity and bimetal synergistic effect,the ultra-thin and continuous mesoporous shell catalyst（Pt Pd-MHS-0.15-0.5）has the best catalytic activity and stability for MOR.In the MOR test,the peak current mass activity of 1.539A/mg _Pt is 2.5 times that of Pt/C(0.619A/mg _Pt),and the specific activity is 2.233 m A/cm²,which is 2.3 times higher than that of Pt/C（0.959m A/cm²）,indicating that methanol oxidation has a faster breaking rate of C-H bond on Pt Pd-MHS-0.15-0.5 catalyst.Compared with Pt/C（0.79）,Pt Pd-MHS-0.15-0.5@m C（1.07）showed higher I_f/I_b value,indicating that the catalyst had better CO tolerance.After 500 cycles,the catalyst reached 69%mass activity retention and showed good stability.At the same time,this synthesis strategy also has a certain universality,and it can be extended to prepare many other platinum-based alloy catalysts with ultra-thin mesoporous shells by selecting appropriate metal precursors.（2）Ordered mesoporous Pt Pd alloy coating catalysts（CNTs@m C@m Pt Pd）supported on carbon carriers were synthesized using a molecular-mediated interfacial co-assembly strategy,in which CNTs provides high conductivity,nitrogen-doped mesoporous carbon provides excellent mass transfer and ordered mesoporous Pt Pd coatings expose a large number of active sites.In the MOR test,the thinner the mesoporous coating is,the better the activity is.Therefore,the nanofiber catalyst with ultra-thin and intact coating Pt Pd alloy（CNTs@m C@m Pt Pd-8）shows excellent MOR catalytic activity and stability.The mass activity and specific activity of 1.557A/mg _Ptand 3.841m A/cm² are 2.5 and 4 times higher than those of Pt/C catalysts(0.619A/mg _Ptand 0.959m A/cm²),respectively.Compared with Pt/C（0.79）,CNTs@m C@m Pt Pd-8has a higher I_f/I_b value of 1.05,and the oxidation potential of CO at 0.812V is much lower than that of Pt/C at 0.87V,indicating that the catalyst has better resistance to CO poisoning.The activity retention rate reached 69%after 500 cycles of CV.It shows that this molecular-mediated synthesis design provides a new idea for the manufacture of mesoporous metal coating materials.