Study Of Pd Based Anodic Catalysts For Alkaline Direct Methanol Fuel Cell

NiO,Ce_xPr_1-xO_2-δ and MnO₂ were prepared by impregnating, sol-gel and hydrothermal method, respectively. Then these oxides and Pd were mixed to make the PdMOx/C(M=Ni,CexPr1-x,Mn) catalysts by chemistry reduction in aqueous solution.Several techniques such as XRD, XPS, BET, cyclic voltammetry(CV), chronoamperometry, chronopotentiometry and A. C. Impedance were used to study the physical properties and electrochemical performances of the in-house synthesized catalysts.For PdNiO/C, The catalyst prepared at such condition presents the highest activity: reduction temperature is 70℃, the ratio between Pd and Ni is 8:2, Reducing Agent is NaBH4, real-time adjust the value of pH when adding PdCl2 solution. The optimal PdNiO/C catalyst shows higher catalytic activity and extremely good poisoing-tolerative compared with the Pd/C catalyst with the same account of Pd loading. By heat-treatment, the NiO is disengaged from Pd lattice, the particle size of catalysts increase, and the catalytic activity of catalyst which is provided with higher crystalline and lower dispersing reduce.For PdCe_xPr_1-xO_2-δ/C(x=0.7) catalysts, the performance is in term of this order: 900℃>700℃>500℃>no heat-treatment. When Ce:Pr=7:3, ratio between Pd and the oxide is 2:1, The sample exhibit the highest activity. Reduction temperature is irrelevant to the performance. When the x=0.7, Pr3+ inter the lattice of CeO2 completely. A great deal of oxygen-hole forms in the catalysts by adding Pr6O11. It is favorable to form sample with high dispersing and small particle size. All factor above get the PdCe_xPr_1-xO_2-δ(x=0.7) catalysts more powerful to the electro-oxidation of methanol and CO. The real area of catalyst do not increase by adding Pr6O11.For PdMnO₂/C, when the ratio of KMnO₄ and MnSO4 is 3:1 (at. %). the ratio between Pd and MnO₂ is 5:1, the catalyst presents the highest activity. Compared with the Pd/C catalyst, the optimal PdMnO₂/C catalyst shows higher catalytic activity and extremely good poisoing-tolerative. The shape of complex plane plots of the impedance on PdMnO₂/C at different potential is dissimilar. The shape of arc in the high frequency at different potential is similar.