Preparation And Oxygen Reduction/methanol Oxidation Performance Of Carbon-supported Small-particle Copper Catalysts

In order to avoid the environmental pollution caused by the use of traditional energy,we need to develop and utilize advanced new clean energy technologies.Direct methanol fuel cells(DMFCs)have become a power substitute for vehicles and wearable electronic products because they can convert chemical energy into electrical energy using the chemical reaction of regenerative fuel(methanol).Currently,the commonly used catalyst material for DMFC anode(methanol oxidation reaction,MOR)and cathode(oxygen reduction reaction,ORR)is commercial platinum carbon(Pt/C),which has high cost,slow catalytic kinetics for cathode ORR,and weak chemical stability.For these reasons,researchers still need to make huge efforts for commercializing DMFC.In addition,in order to effectively improve the electrochemical performance of materials and maximize the utilization of active center atoms,transition metals that play a major catalytic role can be prepared in the form of ultra-small particles.Firstly,Cu-NAC catalyst with a high degree of graphitization was obtained by anchoring small particles of Cu on the precursor activated carbon(AC)for ORR and Pt carrier MOR.Pt was uniformly loaded onto the surface of Cu-NAC through the sodium borohydride reduction process to prepare the Pt-Cu-NAC catalyst for MOR.Cu-NAC is rich in micropores and mesopores and has high specific surface area(894 m~2/g);N is successfully doped into AC,thereby forming effective active sites through Cu-N coordination.The activity of Cu-NAC-3 is the highest in the ORR test,and the reduction peak corresponds to a potential of 0.84 V(onset potential E₀=0.91V,half-wave potential E_1/2=0.84 V).Moreover,the Tafel slope,R_ct value and methanol tolerance of Cu-NAC-3are all better than those of commercial Pt/C.The electrochemically active surface area of Pt-Cu-NAC-3(ECSA=587.2 m~2 g _Pt^-1)is much larger than that of Pt/C(321.9 m~2 g _Pt^-1)measured by MOR,and Pt-Cu-NC-3 shows a high-quality specific activity of 1134.4 m A mg _Pt^-1and good CO tolerance.Secondly,ORR catalysts and Pt-supported Cu-NC materials were prepared by loading small particles of Cu on macro-porous nitrogen-doped carbon derived from zeolite imidazole framework-8(ZIF-8).The ORR test results show that the reduction peak potential of Cu-NC-3 catalyst is 0.87 V,which is better than that of commercial Pt/C(0.83V),mainly because the three-dimensional macroporous structure of Cu-NC-3 provides the uniform dispersion of the main active species Cu atoms.Sufficient space and abundant diffusion pathways enable fast transport of reaction related-species(O₂,H₂O),reducing overpotentials and generation of intermediates(H₂O₂),thereby enhancing ORR activity.In MOR,the mass activity of Pt-Cu-NC-3 is 1217.4 m A mg _Pt^-1,which is higher than that of Pt/C(752.4 m A mg _Pt^-1).Additionally,after 5000 cyclic voltammetry(CV),the activity maintenance rate(down 27.6%)is also better than Pt/C(down 44.0%).The interaction between small metal particles Cu and Pt nanoparticles is beneficial to the generation of OH^-by water molecules,which can quickly eliminate the adsorbed CO and restore the Pt active sites,thereby improving the MOR performance.This synthetic strategy provides a new idea for the preparation of ORR/MOR catalysts with multiple active single metal atoms supported on ZIFs-derived macrostructures.In this paper,a synthesis strategy based on atomically small particle metal Cu-carbon-based bifunctional catalytic materials was designed,which provides a new idea for the development of cathode/anode catalysts in DMFC.