Effect Of Keggin-type Phosphomolybdates On Electrocatalytic Oxidation Of Methanol

Direct Methanol Fuel Cell(DMFC) have been considered the ideal fuel cell system for portable electronic device due to its advantages, such as high energy density at low operation temperature, safe and no pollution, simple structure. However, technological problems such as low power density due to sluggish oxidation reactions at the Pt-based anode, fuel crossover from anode to cathode electrodes, and the high price and limited supply of the electrode catalysts have yet to be overcome. Thus, it is necessary to improve the activity and CO-tolerence of Pt-based catalyst.Au@Pt/C catalysts were synthesized by"seed"method using carbon black XC-72 as support. The XRD, UV-vis and TEM techniques were used to characterize the prepared core-shell and the monometallic catalysts. Results of all the physical characterizations showed the continuous growth of the Pt shell on the Au core. Optimizing the ratio of Au/Pt through electrochemical method, it can be seen that the best ratio is obtained when Au/Pt is 1 to 1, which have the largest electrochemically active surface area, compare with Pt/C, the current density can be enhanced 43% for the effect of methanol electrooxidation. Moreover, cyclic voltammetric and CO stripping cyclic voltammetry were carried out in 0.5 mol/L H₂SO₄ + 1 mol/L CH₃OH + xμmol/L H₃PMo₁₂O40(x = 0, 10, 40, 100, 200) in order to study CO tolerance of Keggin-H₃PMo₁₂O40 and Au@Pt(1:1). It is found that Au@Pt(1:1) catalyst exhibit better CO tolerance in support electrolyte solutions containing PMo.[{Mn(bpy)(H₂O)₃}{Mo₁₂O₃₄(bpy)₁₂}][PMo₁₂O₄₀]₂·2H₂O (ab. Mn-Mo-PMo) was synthesized by hydrothermal reaction. The complex has been structurally characterized by X-ray single crystal diffractions, IR and TG. Results show that the compound is a 3D supramolecular which has tunnels,2D layered structure is consisted of {MoO₄N₂} and {Mn (bpy) (H2O) 3}, hydrogen bonds connected between the layers and layer , Keggin anion as a template embedded in the tunnel. Pt/C was systhesized by polyol-based colloid method. Pt/C catalyst has good dispersion and narrow size of 2.8 nm. Meanwhile, combining the new assist catalyst with Pt/C through the physically mixing method to form different mass percentage of new complex. The results of cyclic voltammetric and CO stripping cyclic voltammetry indicate that the Mn-Mo-PMo not only enhance the activity of methanol electrooxidation but also improve the CO-tolerence, and the best mass percentage is about 4% to 9%; the highest current density is 335 mAmg-1Pt; compare with Pt/C, the result of methanol electrooxidation increased 12%.