High Efficiency Direct Liquid Fuel Cell Catalyst Based On Iron Phosphide Promoter

Nano-structured Pd(Pt)catalysts are generally considered as the most potential anode catalysts for direct liquid fuel cells by far.However,Pd(Pt)-based catalysts are limited by the high cost,low tolerance to CO poison with agglomeration problem of nanoparticles,which these shortcomings all serverly impede their commercialization in the near future.To resolve those challenges before practical application,it is critical to develop an inexpensive catalysts with high dispersity,activity and stability for direct liquid fuel cells.Accordingly,this thesis aims to construct new,efficient and stable anode catalysts for direct liquid fuel cell with using Pd(Pt)nano particles on iron phosphide support.These composite catalysts have been synthesized through a facile glycol reduction method.Their structures and compositions were characterized by using transmission electron microscope together with powder X-ray diffraction and X-ray photoelectron spectroscopy.In addition,the electro-catalytic properties of these composite catalysts were analyzed systematically through cyclic voltammetry,chronoamperometry and electrochemical impedance spectroscopy.Detailed research contents are listed as follows:(1)Petaloid Fe2P with abundant surface defects and large specific surface area was prepared by solid phase reaction.Due to the metal-support coupling interaction,it can anchor and immobilize the as-formed Pt nanocrystals,and therefore enhances the electronic effects between Pt and Fe2P.According to the d-band center theory,higher electron density on Pt surface can effectively reduce the adsorption capacity of CO as well as other toxic intermediates.With the advantages owing to petaloid structure and surface defects of Fe2P,more anchor sites were created and the dispersion of Pt nanoparticles could be improved.Thus,it increased the effective contact between catalyst and reactant,which the charge transfer rate of catalyst in the electrochemical reaction process is also accelerated.As a result,the Fe2P supported Pt catalyst exhibits a boosted catalytic performance for electro-oxidation of alcohols.(2)A PtRu/FeP composite catalyst was synthesized via a simple glycol reduction method.It was reavealed that the as-prepared PtRu/FeP(1:1)catalyst exhibited preferable catalytic stability,high kinetics and low charge transfer resistance.This could be attributed to its unique core-shell structure,high dispersity,strong electronic effect and bi-functional mechanism.The mass-and specific-activity of PtRu/FeP(l:l)catalyst toward electro-oxidation of methanol and ethanol were lmpovea significally comparing to that of PtRu/C-H and PtRu/C-JM catalysts.(3)Using2d-FeP as precursor,we synthesized PdO-Pd/FeP composite catalyst through annealing treatment.The efficiency of formic acid electro-oxidation with using PdO in Pd-FeP system that generated at different annealing temperatures was investigated and discussed.It was realized that PdO,Pd/FeP-250 catalyst displayed the highest catalytic activity and stability when the annealing temperature is 250 ?.Further study indicates that the PdO-Pd/FeP-250 catalyst possesses new active surface.Combinding with the electronic effect between Pd and FeP,the adsorption of reactive oxygen species by FeP can effectively promote the oxidation of toxic intermediates.