Development of Oxide Modified Nanostructured Carbon Materials for using as Electrocatalyst Supports in Hydrogen/Oxygen Fuel Cell Electrodes

A. CONTRERAS; B. LOMBARDI; W.E. TRIACA; S.G. RAMOS; D.R. BARSELLINI; R. CALZADA; A. SCIAN

Buenos Aires

Congreso; 20th Topical Meeting of the International Society of Electrochemistry; 2017

International Society of Electrochemistry

The polymer electrolyte membrane fuel cell (PEMFC) is a promising technology for efficient energy conversion. However, both durability and cost of the membrane are still obstacles for its commercialization. In this regard, the current research is focused on the development of new supports and coverings to improve the life time of the catalytic layer, the self-humidification of the membrane-electrode assembly (MEA) and the electronic properties of the active layer [1-3]. In this work, the results of the performance of three different nanostructured support materials for platinum electrocatalysts used in PEMFC are presented. These materials were: i) nanoporous composite with SiO2-C composition, ii) mesoporous carbon with non-crystalline subgraphitic structure (MPC), and iii) tin and silicon binary oxide modified MPC. The SiO2-C composite was synthetized by using a sol-gel technique with a phenolic resin and alcoholic solution of TEOS as precursors. The product obtained is a composite material with two different crosslinked frameworks, one of amorphous SiO2 and the other of a carbonaceous subgraphitic structure, as determined by XRD. The MPC is obtained through dissolution of the SiO2 network by using HF treatment. Finally, the MPC is covered with a binary tin and silicon oxide by a method similar to that used to obtain the composite, using SnCl4 and TEOS as precursors. The polycrystalline Pt catalysts were deposited on the supports by means of the urea-polyol method, by using ethylene glycol as solvent and urea as precipitant agent. The amounts of H2PtCl6 and support material were adjusted to obtain powders with 20 wt. % Pt. The characterization of the supports and catalysts were made by using XRD, TEM, SEM and voltammetry techniques. The PEMFC performance was evaluated by means of making different MEA with synthetized materials, where the Pt load was adjusted to 0.1 mg/cm2 .The geometric area of the electrodes was 9 cm2. The catalyst stability was evaluated by a potentiostatic technique, where a potential of 1.2 V was applied to the cathode respect to the anode during 320 h. The cathode was fed with N2 and the anode with H2. The SEM images of the composite and MPC show characteristic spongiform structures. The TEM images of binary oxide modified MPC show that the oxide is deposited as a thin layer on the carbon substrate. The average particle size determined by TEM for all the materials is 5.3 + 0.6 nm. The decrease in electrochemically active area was determined by in-situ voltammetry before and after the stability test. Decreases in active area of 63 % for the MPC supported catalyst, 58 % for the SiO2-C composite supported catalyst and 51 % for the binary oxide modified MPC supported catalyst, were found. The results show that oxide layer modification improves the long time stability of the catalyst, whereas binary tin and silicon oxide modified MPC exhibits the best performance, making it a suitable substitute for the Vulcan XC-72 support.