Study On Pd-Based Catalysts Prepared By Phase Transfer Method And Their Electrocatalytic Properties

Direct methanol fuel cell(DMFC)directly converts the chemical energy of methanol into electrical energy,which is characterized by high efficiency,cleanliness and portability.It has a broad application prospect in the field of portable power supply,which is characterized by high efficiency,cleanliness and portability.It has a broad application prospect in the field of portable power supply.However,catalysts for methanol oxidation(MOR)reaction at DMFC anode and oxygen reduction(ORR)reaction at cathode are mainly Pt based catalysts,and high-cost catalysts hinder the industrialization of DMFC.Therefore,the development of high-performance and low-cost non-Pt catalysts is crucial for the development of DMFC technology.Pd is the most promising metal to replace Pt catalyst due to its similar structure and properties and relatively low price,but its catalytic activity and stability are still far from that of Pt?This paper is based on the characteristics that the dielectric constant of the solvent affects the reduction rate of metal precursor,and regulated the structure of Pd catalysts to explore the effects of catalyst composition on structure.The purpose is synthesis of high efficiency,cheap non-Pt catalysts,and revealed the structure-activity relationship of structural properties of the nanoparticles and the electrocatalytic activity.A series of well-dispersed PdnV/C(1,2,3,4,5)nanoparticles were prepared by phase transfer method in dichloromethane using tetrabutylammonium hydroxide(TBAOH)as a phase transfer agent.It was confirmed that V in the PdnV/C exists in the form of VOx,which form the Pd-O-V junction with Pd at the interface.The electronic structure of Pd was regulated,that can improve the catalytic activity for ORR.Especially,Pd4V/C shows higher initial potential(Eonset= 1.027 V),excellent methanol crossover tolerance(98.03%retained)and long-term stability(81.30%related),which are comparable with Pt/CJM.In order to compare with the organic phase preparation of catalyst,PdnV/C(n=1,2,3,4,5)was prepared by using TBAOH as a surfactant in an aqueous solution.It was found that V in PdnV/C prepared in the aqueous phase may build the junction formation of Pd-V,the geometry and electronic structures of Pd were adjusted to improve the ORR catalytic activity of the catalyst;Based on the effects of two kinds of junction formations of Pd and V(Pd-O-V and Pd-V)on the catalytic performance of ORR,combined with density functional theory(DFT)calculation,it was found that the introduction of V reduces the d-band center of Pd,while the d-band center of Pd-O-V(-2.77 eV)is lower than that of Pd-V(-2.00 eV),which weakens the adsorption energy of the oxygen-containing intermediate,thereby improving the catalytic performance of ORR.Different ratios of PdnIr/C(n=1,2,3,4,5)were prepared by phase transfer method.It was found that surface enrichment of Pd formation,a structure similar to Ir@Pd,it has better electronic structure than PdIr alloy in bulk phase,reveals the influence of nanoparticle composition on surface segregation degree,and the relationship between segregation and ORR and MOR catalytic performance is explored;...