Use of Dendrimers during the Synthesis of Pt-Ru Electrocatalysts for PEM Fuel Cells: Effects on the Physical and Electrochemical Properties

In this work, Pt-Ru catalysts were synthesized by a novel methodology which includes the use as encapsulating molecules of dendrimers of different generation: zero (DN-0), one (DN-1), two (DN-2), and three (DN-3). Synthesized catalysts were heat-treated at 350°C, and the effects of this treatment was established from the physical (X-ray dispersive energy (XDE) and X-ray diffraction (XRD)) and electrochemical characterization (cyclic voltammetry and chronoamperometry). Results showed that the heat-treatment benefits the catalytic properties of synthesized materials in terms of CO and methanol electrochemical oxidation. The curves for CO stripping were more defined for heat-treated catalysts, and methanol oxidation current densities were higher for these materials. These changes are principally explained from the removal of organic residues remaining on the surface of the Pt-Ru nanoparticles after the synthesis procedure. After the activation of the catalysts by heating at 350°C, the real importance of the use of these encapsulating molecules and the effect of the generation of the dendrimer become visible. From these results, it can be concluded that synthesized catalysts are good catalytic anodes for direct methanol fuel cells (DMFCs)

Pyrolysis towards the manufacturing of valuable products

Pyrolysis of coal or any carbonaceous material is a good method for producing valuable products such as gases, liquids and char. It has the advantage, versus other conversion technologies, of promoting the transfer of hydrogen from the parent material to the gas and the liquid products, concentrating the carbon in the residual char which can be an important improvement in the present scenario, in which carbon-free or at least low carbon fuels need to be promoted to reduce CO2 emissions. In this sense, pyrolysis has been claimed as an alternative to incineration or land filling for valorization of wastes of hydrocarbon nature. Yields and composition of each product fraction obtained after pyrolysis depend not only on the reaction conditions but also on the experimental system used for the process. In general, the liquids contain a complex mixture of compounds of 5-20 carbons with a high proportion of aromatics that can be used directly as fuels or as petroleum refinery feedstocks. The gas fraction which can also be used as a fuel is composed mainly of hydrogen and light hydrocarbons. The solid products present unique features for the utilization as sorbents or as catalyst supports by the preparation of granulated activated chars, briquettes and carbon coated monoliths, with advanced textural and chemical properties