Synthesis And Performances Investigation Of Carbon Supported Multimetallic Electrocatalyst

At present, the study of direct methanol fuel cells(DMFC) has made great progress, but the development of commercial DMFC has been hindered by some important technical issues. Technically, some problems, such as low electrocatalytic activity of the catalysts and high cost of both catalysts and overall DMFC restrict its partical application. Therefore, the study of the catalysts with performance is an important study subject in commercial DMFC application.In this paper, for the preparation of DMFC catalyst, the microwave assisted polyol reduction process was used to synthesize PtxAgy/CNTs, PtAgxCoy/CNTs,AgxCoy/CNTs catalysts. The morphology, crystal structure, electrochemical activity of the catalysts were detected by material characterization and electrochemical investigation methods. The main results obtained are as follows:1) The X-ray diffraction(XRD) results demonstrate that, the alloy phase of the three kind’s catalysts was detected. In an acidic electrolyte, the methanol oxidation catalytic activity of the PtxAgy/CNTs catalysts increase with the increase alloying. PtAg3/CNTs catalyst showed the biggest electrochemically active surface area(ECSA) of 134.4 m2/g. Electrochemical studies the methanol oxidation showed that the PtAg3/CNTs catalyst had the best catalytic activity and stability for methanol oxidation reaction(MOR), the highest peak current density of 32.1 mA.mg-1 was obtained. In the alkaline electrolyte, the methanol oxidation catalytic activity of the PtxAgy/CNTs catalysts were significantly influenced by silver oxides in the catalysts.2) The PtAgxCoy/CNTs catalysts exhibit higher catalytic activity than the PtxAgy/CNTs catalysts for methanol oxidation reaction(MOR). In an acidic electrolyte, electrochemical measurements showed that the PtAgxCoy/CNTs catalysts had larger electrochemically active surface area(ECSA), and the PtAg3Co/CNTs catalyst showed the highest ECSA of 272.7 m2/g among all of the tested catalysts. As compared to the PtAg3Co/CNTs catalyst, the commercial Pt/C catalyst had a minor one of 266.6 m2/g. Electrochemical studies of the methanol oxidation revealed that, except PtAgCo5/CNTs catalyst, all of the other PtAgxCoy/CNTs catalysts exhibited higher catalytic activity than the commercial Pt/C catalyst, the PtAg3Co/CNTs catalyst, had the best catalytic activity for MOR, showed the highest peak current density of 191.3 mA.mg-1, which was 2 times to the activity of the commercial Pt/C catalyst of 84.2 mA.mg-1. In addition, the kinetic analysis results indicated that the analogous Tafel plots obtained on the PtAgxCoy/CNTs catalysts and the commercial Pt/C catalyst.3) Electrochemical measurements showed that, the AgxCoy/CNTs catalysts had no catalytic activity for the methanol oxidation reaction. In this paper, the catalytic activity, kinetic parameters, stability of oxygen reduction reaction(ORR) has been investigated by Cyclic Voltammetry(CV), Liner Sweep Voltmmetry(LSV) and Chronoamperometry(CA). According to the Koutecky-Levich equation, the electron transfer number(n) of the AgxCoy/CNTs catalysts for ORR was detected to be 3.1 ~ 4.0, under the same conditions, the n of the commercial Pt/C catalyst was 3.8. Furthermore, the stability of the AgxCoy/CNTs catalysts for ORR was dramatically improved by NH3-modified.