The effect of operating conditions on the dynamic response of the direct methanol fuel cell

Nanoporous Platinum/(Mn,Al)3O4 Nanosheet Nanocomposites with Synergistically Enhanced Ultrahigh Oxygen Reduction Activity and Excellent Methanol Tolerance

At present, metal/metal oxide composites are considered as potential oxygen reduction reaction (ORR) catalysts for energy-related applications like fuel cells. Here, we fabricated a high-activity, low Pt loading ORR electrocatalyst composed of nanoporous Pt (np-Pt) in intimate contact with lamellar (Mn,Al)₃O₄ nanosheet (NS). In comparison to Pt/C (Johnson Matthey), the np-Pt/(Mn,Al)₃O₄ NS catalyst shows a 11.5-fold enhancement in the mass-normalized ORR activity and much better methanol tolerance because of the metal-support interactions between np-Pt and (Mn,Al)₃O₄. Furthermore, the combination of electrochemical experiments with theoretical calculations verifies that the ORR on the np-Pt/(Mn,Al)₃O₄ NS catalyst is a direct 4e^- pathway in the alkaline solution. In addition, the electrocatalytic mechanisms have also been rationalized by density functional theory (DFT) calculations.

Platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles as methanol-tolerant oxygen reduction electrocatalysts

Covalent triazine frameworks, which are crosslinked porous polymers with two-dimensional molecular structures, are promising materials for heterogeneous catalysts. However, the application of the frameworks as electrocatalysts has not been achieved to date because of their poor electrical conductivity. Here we report that platinum-modified covalent triazine frameworks hybridized with conductive carbon nanoparticles are successfully synthesized by introducing carbon nanoparticles during the polymerization process of covalent triazine frameworks. The resulting materials exhibit clear electrocatalytic activity for oxygen reduction reactions in acidic solutions. More interestingly, the platinum-modified covalent triazine frameworks show almost no activity for methanol oxidation, in contrast to commercial carbon-supported platinum. Thus, platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles exhibit selective activity for oxygen reduction reactions even in the presence of high concentrations of methanol, which indicates potential utility as a cathode catalyst in direct methanol fuel cells.

Covalent triazine frameworks are known catalysts for some catalytic reactions, but show no electrocatalytic activity. Here, the authors synthesize platinum modified covalent triazine frameworks hybridized with carbon nanoparticles, which are electro-active for oxygen reduction reactions.

Simultaneous electroosmotic and permeation flows through a Nafion membrane

The volume flow of methanol-water potassium chloride solutions through a Nafion membrane originated by the simultaneous action of electric potential and pressure gradients has been measured at different percentages of methanol. Measurements were conducted when both gradients act in the same and in the opposite directions under different experimental conditions. The results indicate that the simultaneous action of the pressure and potential differences originates a total flow different from the sum of the individual electroosmotic and permeation flows due to each force acting separately. The application of the irreversible thermodynamics theory, which includes second-order terms, allowed the study of the influence of the composition of the solutions on the determination of the different phenomenological coefficients.