Study On The Catalysts Preparation And Performances For Micro Mixed Reactant Fuel Cell

The direct methanol fuel cell（DMFC）, with high energy transformation efficiency and environmentally friend, has shown vast application potential in the field of portable electronics. The cost of a DMFC is mainly determinated by the expenditure of the electrocatalysts and the electrode separator, which have became the dominating restriction factors of the commercialization of the DMFC. In this paper, the electrocatalytic performance of the catalysts in DMFC have been studied detailedly, and according to which, the oxygen reduction reaction（ORR） selectivity of nitrogen doped carbon nanotubes（NCNTs） catalyst have been utilized to design a type of low-cost, compact mixed reactant direct methanol fuel cell（MRDMFC）, which reduces the fuel cell cost in electrocatalysts and eliminates the dependence of the conventional alkaline DMFC on an anion exchange membrane.On the side of cathodic catalyst, the NCNTs have been prepared via the microwave plasma chemical vapor deposition（MPCVD） technology. The ORR activities of NCNTs catalysts have been optimized basing on the four processing parameters of microwave power, ammonia flux, chamber pressure and reaction time. And the studing results have shown that the preparation conditions of low microwave power, low chamber pressure and relatively short reaction time are more beneficial to promote the catalytic activities of NCNTs catalysts. The excellent ORR performance of NCNTs are original from the low temperature reaction condition created by the MPCVD technology, which promotes the formation of NCNTs with the high level of superficial defect and the homogeneous distribution of various nitrogen-containing functional groups, thus benefits to O2 molecules absorbing reactionsOn the side of anodic catalyst, the platinum nickel catalysts supported by carbon nanutubes（PtxNiy/CNTs） with different platinum nickel atomic ratio have been prepared via the impregnation-reduction method under room temperature. And the effect of varying platinum nickel atomic ratio on the methanol oxidation performance has been studied in detail. The studing results have shown that as to PtxNiy/CNTs catalysts, the utilization ratio of platinum atom improves with the increase of nickel atom content; and the electrochemical activities of PtxNiy/CNTs catalysts have been promoted with the use of nickel atoms while the the expenditure of catalysts efficiently decrease.The catalytic electrodes have been prepared basing on NCNTs and Pt₁Ni₃/CNTs catalysts. The low-cost teflon membrane filter, as the electrode separator and the single permeable cathodic feeding mode are employed to study the effect of operating conditions on the performance of the fuel cell, including methonal concentration, reactant fluxing rate and electrolyte concentration. The experimental results suggest that the optimal operating conditions of this fuel cell are 3 M methanol, 0.5-1 mL min^-1 fluxing rate and the KOH concentration of 0.1 M. The maximum open circuit potential of the testing fuel cell is 0.351 V and the maximum power density is 0.151 mW cm^-2.