Carbon materials for the electrochemical storage of energy in capacitors

https://digital.csic.es/bitstream/10261/113789/1/Production_carbon_Sevilla.pdf

The production of carbon materials by hydrothermal carbonization of cellulose

Microfibrillated cellulose - its barrier properties and applications in cellulosic materials: a review.

Electrochemistry will play a vital role in creating sustainable energy solutions in the future, particularly for the conversion and storage of electrical into chemical energy in electrolysis cells, and the reverse conversion and utilization of the stored energy in galvanic cells. The common challenge in both processes is the development of-preferably abundant-nanostructured materials that can catalyze the electrochemical reactions of interest with a high rate over a sufficiently long period of time. An overall understanding of the related processes and mechanisms occurring under the operation conditions is a necessity for the rational design of materials that meet these requirements. A promising strategy to develop such an understanding is the investigation of the impact of material properties on reaction activity/selectivity and on catalyst stability under the conditions of operation, as well as the application of complementary in situ techniques for the investigation of catalyst structure and composition.

Oxygen electrochemistry as a cornerstone for sustainable energy conversion

To increase their electrochemically active surface area, catalysts supported on high surface area materials, commonly carbons, are widely used in low-temperature fuel cells. Recent studies have revealed that the physical properties of the carbon support can greatly affect the electrochemical properties of the fuel cell catalyst. It has been reported that carbon materials with both high surface area and good crystallinity can not only provide a high dispersion of Pt nanoparticles, but also facilitate electron transfer, resulting in better device performance. On this basis, novel non-conventional carbon materials have attracted much interest as electrocatalyst support because of their good electrical and mechanical properties and their versatility in pore size and pore distribution tailoring. These materials present a different morphology than carbon blacks both at the nanoscopic level in terms of their pore texture (for example mesopore carbon) and at the macroscopic level in terms of their form (for example microsphere). The examples are supports produced from ordered mesoporous carbons, carbon aerogels, carbon nanotubes, carbon nanohorns, carbon nanocoils and carbon nanofibers. The challenge is to develop carbon supports with high surface area, good electrical conductivity, suitable porosity to allow good reactant flux, and high stability in fuel cell environment, utilizing synthesis methods simple and not too expensive. This paper presents an overview of carbon supports for Pt-based catalysts, with particular attention on new carbon materials. The effect of substrate characteristics on catalyst properties, as electrocatalytic activity and stability in fuel cell environment, is discussed.

Carbon supports for low-temperature fuel cell catalysts

Cellulose-based aerogels

Pt-doped carbon aerogels have been prepared following two methods. In the first, the electrocatalytic material was synthesized from the sol–gel reaction precursors 2,4-dihydroxybenzoic acid and formaldehyde. The platinum precursor was Pt(NH3)4Cl2, ion-exchanged onto the gel surface. The doped gel was dried supercritically and pyrolyzed at high temperature. This material was characterized with transmission electron microscopy (TEM) and by X-ray diffraction (XRD). The size distribution of the Pt nanoparticles changed with the pyrolysis temperature but the range of the size distribution did not. Platinum accessibility and electroactivity were evaluated with voltammetry. The second kind of Pt-doped carbon aerogels was synthesized from resorcinol and formaldehyde, supercritically dried, and pyrolyzed. The ground carbon aerogel was impregnated with a platinum precursor H2PtCl6 aqueous solution. This platinum salt was chemically reduced with NaBH4. Two carbon blacks, Vulcan XC-72 and BP2000, were doped following the same technique so that the influence of the carbon type on the properties of the deposited platinum nanoparticles could be investigated. The Pt-doped carbons so obtained were characterized with TEM, XRD, hydrogen-adsorption/desorption cyclic voltammetry, CO-stripping voltammetry, and oxygen reduction reaction (ORR) activity. The Pt-doped carbon aerogel exhibited high ORR specific activity but comparable mass activity as compared with Pt-doped carbon blacks.

Sandrine Berthon-Fabry

Papers

Cellulose-based aerogels

Highly dispersed platinum on carbon aerogels as supported catalysts for PEM fuel cell-electrodes: comparison of two different synthesis paths

Use of cellulose-based carbon aerogels as catalyst support for PEM fuel cell electrodes: Electrochemical characterization

Functionalisation and chemical characterisation of cellulose-derived carbon aerogels

Carbon xerogels as catalyst supports for PEM fuel cell cathode