Research Of Anode Pt-based Catalysts For Direct Methanol Fuel Cell

Direct methanol fuel cell (DMFC) is one of the most desirable power source for small-scale power units because of inexpensive fuel, ease of handling, high theoretical energy density and near-zero pollutant emission.However, there is large distance between the practical DMFC performance and the theoretical performance. Synthesizing and searching for electrocatlasyts with high activity are the important approach to improve DMFC performance, which also become to be the endlessly goal for researchers.At present, Pt-based catalysts are still used as electrocatalysts most widely in DMFC.Generally, Pt-based catalysts are prepared supported on carbon materials of conductive and high surface area. How to synthesize Pt-based nanoparticles with appropriate particle sizes, homogenous distribution and how to improve noble metal utilization effectively have important sense for DMFC.In this thesis, activated black carbon Vulcan XC-72 are used as supports in the preparation of Pt-based catalysts for fuel cell.High dispersion of PtRu alloy nanoparticles, PtRuNi alloy nanoparticles, PtRuCo alloy nanoparticles and low Pt decorated Ru nanoparticles supported on Vulcan-72 are prepared.Particle size, the appearance, electrochemistry activity and the stability of carbon supported metal catalysts are researched. The main topics and results of the thesis are sunnarized as follows:Using Vulcan XC-72 as supports and sodium citrate as a stabilizer, 20 wt% PtRu/C was prepared by impregnating reduction method. EDS, TEM and XRD were applied for characterizing catalysts. Catalytic activity and stability were studied in methanol solution by using different pH value and the method of pre-adsorbed CO monolayer stripping was used to research their anti-poisoning ability. The results showed that the preparation of PtRu/C for methanol had the highest catalytic activity and stability when pH value was 8. Compared with commercial Pt/C, the pre-adsorbed CO monolayer oxidation potential significantly negative shifted.Using Vulcan XC-72 as supports, sodium citrate as a stabilizer, 20wt% Pt60Ru30Ni10/C was prepared by impregnating reduction method. EDS, TEM and XRD were applied for characterizing catalysts. Catalytic activity and stability were studied in methanol solution by using different pH value. The results showed that the preparation of Pt60Ru30Ni10/C for methanol had the highest catalytic activity and stability when pH value was 8.Using Vulcan XC-72 as supports, sodium citrate as a stabilizer, 20wt% Pt60Ru30Co10/C was prepared by impregnating reduction method. EDS, TEM and XRD were applied for characterizing catalysts. Catalytic activity and stability were studied in methanol solution by using different pH value and the method of pre-adsorbed CO monolayer stripping was used to research their anti-poisoning ability. The results showed that the preparation of Pt60Ru30Co10/C for methanol had the highest catalytic effect when pH was 8, and its catalytic activity and stability were much higher than commercial Pt50Ru50/C. Compared with Pt50Ru50/C, the pre-adsorbed CO monolayer oxidation potential significantly negative shifted.Carbon-supported Ru nanoparticles were decorated with low Pt by spontaneous deposition method. TEM indicated that the average particle size of catalyst was about 4nm with excellent dispersion and the XRD analyzing results showed that Pt had decorated on surface of Ru. The enhance CO tolerance was studied by pre-adsorbing CO striping voltammetric curves in 0.1M HClO4. Catalytic activities of the prepared Pt/Ru/C were studied by cyclic voltammetry in a solution of 0.5 mol/L CH3OH + 0.1 mol/L HClO4. The results showed the oxidation peak current is far more than 20wt% RuPt/C (E-TEK) and 20wt% Pt/C (Johnson Matthey). The prepared catalyst not only had a higher catalytic activity to methanol, but also had lower Pt loading.