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

A. CONTRERAS; R. CALZADA; S.G. RAMOS; BÁRBARA LOMBARDI; A. SCIAN; W.E. TRIACA

Buenos Aires

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

International Society of Electrochemistry

The polymer electrolyte membrane fuel cell (PEMFC) is a promisingtechnology for efficient energy conversion. However, both durability and costof the membrane are still obstacles for its commercialization. In this regard,the current research is focused on the development of new supports andcoverings to improve the life time of the catalytic layer, theself-humidification of the membrane-electrode assembly (MEA) and the electronicproperties of the active layer [1-3]. In this work, the results ofthe performance of three different nanostructured support materials forplatinum electrocatalysts used in PEMFCare presented. These materials were: i) nanoporous composite with SiO2-Ccomposition, ii) mesoporous carbon with non-crystalline subgraphitic structure(MPC), and iii) tin and silicon binary oxide modified MPC. The SiO2-C composite was synthetizedby using a sol-gel technique with a phenolic resin and alcoholic solution ofTEOS as precursors. The product obtained is a composite material with twodifferent crosslinked frameworks, one of amorphous SiO2 and the other of a carbonaceoussubgraphitic structure, as determined by XRD. The MPC is obtained throughdissolution of the SiO2 network by using HF treatment. Finally, the MPCis covered with a binary tin and silicon oxide by a method similar to that usedto obtain the composite, using SnCl4 and TEOS as precursors.The polycrystalline Pt catalysts were deposited on the supports by means of theurea-polyol method, by using ethylene glycol as solvent and urea as precipitantagent. The amounts of H2PtCl6 and support material wereadjusted 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 bymeans of making different MEA with synthetized materials, where the Pt load wasadjusted to 0.1 mg/cm2 .The geometric area of the electrodes was 9 cm2. The catalyst stabilitywas evaluated by a potentiostatic technique, where a potential of 1.2 V wasapplied to the cathode respect to the anode during 320 h. The cathode was fedwith N2 and the anodewith H2. The SEM images of the composite and MPC show characteristicspongiform structures. The TEM images of binary oxide modified MPC show thatthe oxide is deposited as a thin layer on the carbon substrate. The averageparticle size determined by TEM for all the materials is 5.3 + 0.6 nm. Thedecrease in electrochemically active area was determined by in-situ voltammetrybefore and after the stability test. Decreases in active area of 63 % for theMPC supported catalyst, 58 % for the SiO2-C composite supportedcatalyst and 51 % for the binary oxide modified MPC supported catalyst, werefound. The results show that oxide layer modification improves the long timestability of the catalyst, whereas binary tin and silicon oxide modified MPCexhibits the best performance, making it a suitable substitute for the VulcanXC-72 support.