Pt -based catalysts of direct methanol fuel cells
|School||Nanjing Normal University|
|Course||Physical and chemical|
|Keywords||Direct formic acid fuel cell Direct methanol fuel cell Pt/C catalyst|
The fuel cell has received considerable attention as the mobile power source because of its high energy conversion efficiency and low pollutant emission. However, low electrocatalytic activity of the anodic and cathodic catalyst, the high cost of Pt-based electrocatalysts, and the degeneration of cathodic Pt-based electrocatalysts originated from fuel molecules crossover are significant barriers to the widespread commercialization of fuel cell. Therefore, the anodic and cathodic catalyst with high electrocatalytic performance is an important study content in Fuel Cell. The mutual relation of the preparation, construct and performance of platinum group metals nanoparticles catalyst are studied in the thesis. The mail research work contain two parts:the preparations of carbon supported Pt metal catalysis, and their electrocatalytic performance for fuel molecules oxidation and oxygen reduction. The main results obtained are as follows:1. The previous reports indicated that during the preparation of carbon supported Pt (Pt/C) catalyst, H2PtCl6 is used as the precursor and ethylenediaminetetraacetic acid (EDTA) is used as the complexing agent. In this paper, it was found that during the preparation of Pt/C catalyst using Pt(NO3)2 as the precursor, EDTA can also effectively reduce the average diameter of the Pt particle and improve the dispersion degrees. However, EDTA can not coordinate with Pt2+, forming the complex and moreover EDTA would wrap Pt2+and then the reduced Pt particles through the electrostatic interaction, leading to that the Pt particles obtained are not easy to be aggregated. The average diameter of the Pt particles in the Pt/C catalyst obtained is only 3 nm and the dispersion of the Pt particles is uniform. Therefore, the Pt/C catalyst obtained has the excellent electrocatalytic activity and stability for methanol oxidation.2. Pt/C catalysts with the different Pt particle size are prepared by using SnCl2 as the reductant and methanol as the organic solvent. This improved preparation method is very simple and inexpensive compared to Bonnemann method. The effect of particles size on the methanol oxidation and oxygen reduction are studied. It is found that the average size of the Pt particles can be controlled by adjusting the evaporating temperature of the solvent. The electrochemical studied show the optimum Pt particles size for formic acid oxidation is 3.8 nm.3. Carbon supported Pt-P nanoparticles (Pt-P/C) catalyst is prepared by ethylene glycolmethod in the presence of white phosphorus. Inductive Coupled Plasma Emission Spectrometer (ICP) results demonstrate that Pt and P atomic ratio in Pt-P/C catalyst is 3:2. X-ray photoelectron spectroscopic (XPS) shows that the content of Pt0 species in Pt-P/C catalysts is about 71.1% by measuring the relative peak areas, and the binding energy of Pt4f has an obvious positively shift, indicating the introduction of P can change the electronic state of Pt. The electrocatalytic performance of the Pt-P/C catalyst for methanol oxidation and oxygen reduction is much better than that of the Pt/C catalyst.