Construction Of Platinum-based Catalyst Composite Supports Modified By Metal-doped Mo₂C And Its Catalytic Behavior For Methanol Oxidation

Energy crisis and environmental pollution are two major problems facing the world today.Therefore,vigorously developing low-cost,pollution-free and sustainable new energy is an effective way to solve this problem.Throughout the research status of new energy,direct methanol fuel cells（DMFCs）have aroused widely attention for its fast start-up,high volumetric energy density,high energy transition efficiency and environmental friendliness.However,the low catalytic activity,poor anti-toxicity and high cost of its anode catalysts have hindered its large-scale application.At present,in addition to the breakthrough in the catalyst,the research on the catalyst support is also continuing.Studies had shown that transition metal carbides（TMCs）had good mechanical properties,can regulate the electrons on the Pt surface and decompose water at low overpotential,which makes TMCs likely to be used as a promising anode catalyst supports for DMFCs.However,the process of synthesizing TMCs generally required reducing gases（such as H₂,CH₄）and extremely high temperatures（≥1000℃）,which tended to cause large-area particle sintering and agglomeration.Therefore,it is necessary to simply synthesize small and uniform TMCs NPs by means of adding self-made carbon or metal regulation,helping the TMCs support to stimulate the catalytic activity and stability of catalyst particles.Based on the above discussion,this paper combined the advantages of carbon materials and TMCs to synthesize Mo₂C series catalyst supports for improving the activity of the catalyst.The specific research contents and results were as follows:Firstly,the glue-like glucose and oxide materials were induced by surfactants and assembled on commercial carbon spheres（CS）,and a series of catalyst supports were constructed by adjusting the metal ratio and the annealing temperature.The results showed that Pt/Co₂C-Mo₂C@CS catalyst had more active sites and showed outstanding catalytic activity(1504.5 m A mg _Pt^-1)when the metal ratio was 1:1 and annealing temperature was 900℃.The retained mass activity was 131 m A mg_Pt^-1 after 3600 s under the potential of 0.6 V by chronoamperometry（CA）.Under the action of bi-functional mechanism,the CO tolerance of this catalyst was also superior to Pt/C-H catalyst.Physical characterization proved the existence of TMCs and their uniform distribution.Due to the metal-support interaction,the Pt element d-bond decreased electrons,which affected the oxidation potential of Pt-CO_ads adsorbates.Secondly,based on the above research results,considering that long-term immersion of the CS support in the working environment would cause structural collapse and corrosion,resulting Pt loss and agglomeration,etc.,the purpose of stabilizing the structure is achieved by introducing carbon materials derived from MOFs with special morphologies.Therefore,the bimetallic oxide nanorods（BMO NRs）were used as the precursors,on which ZIF-8@ZIF-67 polyhedra were spontaneously grown.After calcination at high temperature,the obtained material（Ni Co-Mo₂C@NDC）had obvious auxiliary catalytic effect as a support for MOR catalyst.Physical characterization proved that:（1）The bimetallic oxide nanorods（BMO NRs）and polyhedral MOFs materials were successfully synthesized;（2）After calcination at high temperature,the smooth MOFs became wrinkled polyhedra and accompanied by the generation of nanotubes.Electrochemical tests showed that the mass activity of Pt/Ni Co-Mo₂C@NDC catalyst was as high as 1538 m A mg _Pt^-1,which was 3.9 times higher than that of commercial Pt/C(393 m A mg _Pt^-1),and was also much higher than that of pure MOFs material(660 m A m A mg _Pt^-1).The stability of the catalyst is obviously better than that of other catalysts.These works provide ideas for solving the problem of low MOR activity,which is beneficial to the further in-depth discussion of the whole DMFCs system.