Study On Catalytic Oxidation Of Methanol Formic Acid By Precious Metal Modified NPG Catalyst

In recent years, people are attracted by the advantages of direct methanol fuel cell(DMFC) and direct formic acid fuel cell(DFAFC) of low cost, wide fuel source, transport and storage safety,but the catalytic activity of the anode catalyst are low, and methanol and formic acid oxidation intermediate product will generate carbonyl that lead the poisoning effect of the anode catalyst, resulting in the actual development speed of DMFC and DFAFC has been slow. Therefore, the research and development of high catalytic activity, anti poisoning ability of the new catalyst has become a key technology in the DMFC development. A large number of research have found that it is possible to improve the platinum catalyst by the synergistic effect of multiple metal mingled to develop the activity and stability, which is made of platinum based composite catalysts(such as Pt-Ru, Pt-Sn, Pt-Ni, Pt-Ir etc.). First the direct electrochemical deposited method is adopted with nanoporous gold film(NPG) as the carrier, the electrochemical deposition method can realize selective deposition of metal catalyst in both the electronic channel, and ion carrier transmission channel and proton membrane contact, shows the catalyst is higher than the traditional method based on proton exchange membrane electrolyte solution adhesive on Pt/C catalyst utilization rate.Secondly, the study found that the addition of the second metal is not only as a kind of bifunctional oxygen electrode catalyst group, but also as the anode catalyst of direct alcohol fuel cell has better performance of anti poisoning.Therefore, the constant potential deposition technology is used to add Ir, Ni, Bi in the Pt NPG, so Pt/M NPG catalyst were obtained, electrochemical performance test of methanol and formic acid using a series of catalyst solution containing Pt, in a series of amount of substance M in the different proportion of potentiostatic deposition preparation forms, the results show that the based on Pt electric-catalyst of the added amount of Ir、Ni、Bi increased for the electrocatalytic oxidation of methanol, formic acid, NPG is better than that of the pure Pt catalyst, and has a good cycle life time, and stability.In this paper, H2PtCl6.6H2 O and IrCl3.3H2 O, H2PtCl6.6H2 O and NiSO4.6H2 O, H2PtCl6.6H2 O and BiNO3.5H2 O are used as the metal source, NPG is used as substrate, electrodeposition method is used to prepare of two composite nano catalyst NPG/PtIr, NPG/PtNi, NPG/PtBi that have high activity, and XRD and SEM technique are used for the characterization of the catalyst particle size, crystallinity, the electrochemical method evaluation NPG/PtIr, NPG/PtNi, NPG/PtBi catalyst for methanol formic acid electro catalytic oxidation activity and stability. The main results are as follows:First of all, in the three electrode system, constant potential co-deposition method is adopted on preparation of NPG/PtIr, NPG/PtNi, NPG/PtBi catalysts with high dispersion, using XRD and SEM technique for the characterization of catalyst particle size、dispersion state of modified NPG membrane with PtIr, PtNi, PtBi. The results showed the highly dispersed PtIr film the surface of NPG to form the style that the package was in the catalyst surface of NPG film, PtNi, PtBi formed flower and button shaped particles were on the convex surface of NPG. By cyclic voltammetry, electrochemical method for evaluating the activity and stability of electrode catalyst for methanol, formic acid electro catalytic oxidation. Testing results showed that the electrocatalytic oxidation of NPG/PtIr and NPG/PtBi catalysts for methanol, formic acid showed good activity and stability, of NPG/PtNi catalyst for methanol showed good activity and stability. This is mainly due to synergistic catalytic effect between Pt, M and NPG of the methanol, formic acid oxidation intermediate product poisoning species easily results oxidized into the final product, followed by groups of the catalyst prepared by this method has smaller particle size, and well dispersed.The electrochemical properties of Pt/Ir NPG catalyst display the rate of Pt:Ir=3:2 which has the best performance for the electrocatalytic oxidation of methanol, direct formic acid fuel cell, in which Pt/Ni NPG Pt:Ni=1:1 catalyst has the best performance for the electrocatalytic oxidation of methanol, direct formic acid fuel cell, in which Pt/Bi NPG Pt:Bi=9:1 catalyst has the best performance for the electrocatalytic oxidation of methanol, direct formic acid fuel battery.This thesis developed several electrocatalytic oxidation of the two element composite nano structure of electric catalyst for methanol and formic acid which has high catalytic activity and stability. At the same time, reducing the load of noble metal Pt, the introduction of Ir, Ni, Bi makes the catalyst CO-poisoning further increase, the research shows that the two element composite nano catalysts have good prospect in DMFC and DFAFC.