High performance PEM fuel cell catalyst layers with hydrophobic channels

Polymer electrolyte membrane fuel cell performance has been enhanced with efficient water management by modification of the structure of the catalyst layer. Polytetrafluoroethylene (PTFE) was added to the catalyst layer structure by using two-step catalyst ink preparation method. Physical and electrochemical characterization of catalyst layers with hydrophobic nanoparticles were investigated via TGA-DTA, XRD, nitrogen physisorption, SEM, TEM, EDX analysis, and cyclic voltammetry technique. In addition, performance tests of MEAs were carried out. Catalyst layer structure after performance tests was observed by SEM analysis. Tubular open-ended mesopores have been constructed through the catalysts with hydrophobic nanoparticle addition. PTFE addition to the catalyst layer structure decreased both electrochemical surface area and Pt utilization. Mesoporous hydrophobic channels in the catalyst layer provided decreasing mass transport limitations at higher current densities, by this way, power density of Pt/C-Nafion/PTFE catalyst enhanced. It is concluded that mesoporous hydrophobic channels through the catalyst layer facilitate water removal. Copyright (c) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

PEM Yakıt pilleri için kompozit membranlar ve elektrokatalizörlerin geliştirilmesi ve uzun dönem performanslarının belirlenmesi

TÜBİTAK MAG01.11.2012Proton değişim membranlı (PEM) yakıt pilleri, hidrojen enerji sisteminin en önemli cihazlarından biridir. Her geçen gün ticari uygulaması yaygınlaşmaktadır. Bu yeni teknolojinin gelişiminde yer almamız önemlidir. Bu projenin amacı PEM yakıt pillerinin en önemli elemanı olan membran elektrot bileşimini oluşturan proton iletim özelliğine sahip zarların iyileştirilmesi, etkin karbon destek yapıların ve elektrokatalizörlerin hazırlanması, elektrot üretim teknolojisinin geliştirilmesi ve bu malzemelerin uzun dönem dayanıklılık testlerinin gerçekleştirilmesidir. PEM yakıt pilinde en çok kullanılan proton iletken zar, Nafion‟a, nano boyutta TiO2 ve SiO2 katkı malzemeleri eklenmesiyle elde edilen nano kompozit membranla PEM yakıt pilinin çalışma sıcaklığı arttırılmıştır. Nano boyutta inorganik madde eklenmesiyle polimer ve inorganik partiküller arasında yüksek spefisik etkileşim yüzeyi sağlanmış ve yüksek sıcaklıklarda (80-110oC) membran yapısında bulunan kimyasal suyun dehidrasyonu önlenmiştir. Ayrıca membranın ısıl ve mekanik kararlılığı arttırılmıştır. Bu projede por yapısı silisyum bazlı bir kalıpla hazırlanan ve daha sonra bu yapının karbona dönüştürülmesiyle oluşturulan, içi boşluklu mezo gözenekli kabuk yapılı karbon destek malzemesi hazırlanmıştır. Bu malzemeye Pt nanoparçacıklar tutturularak özgün bir elektrokatalizör elde edilmiştir. Çevrimsel voltametri tekniğiyle elektrokatalizörlerin hidrojen oksidasyon ve oksijen redüksiyon reaksiyon aktiviteleri belirlenmiştir. Geliştirilen kompozit membranlar ve elektrokatalizörlerin uzun süre dayanıklılık testleri uluslararası kabul gören protokollere göre pil içinde ve pil dışında yapılan testlerle belirlenmiştir. Bu proje sonucunda ülkemizde PEM yakıt pilinin en önemli parçası olan membran–elektrot bileşenlerini en son teknolojiyle üretilebilir bilgi ve teknolojik birikim sağlanmıştır.Proton exchange membrane (PEM) fuel cell is one of the most important device for hydrogen energy system where hydrogen energy is providing a sustainable, clean and renewable energy use. Commercialization is spreading over day by day. We should be involved in this technological development. Membrane electrode assembly is the key part of PEM fuel cells; therefore the aim of this project is to improve its components such as to modify the proton exchange membrane, prepare new electrocatalyst, carbon support where as to develop a new electrode manufacturing method and to determine long term durability of these components. Operating temperature of PEM fuel cells are increased by the preperation of.nanocomposite polymeric membranes with the addition of nano-sized, TiO2, SiO2 into Nafion. Incorporation of nano sized inorganic materials in the membrane structure provided high specific interactions between the polymer and inorganic particles, and prevented loss of chemical water in the structure at high temperatures (80-110oC). Beside, thermal and mechanical stability of membrane have been improved. In this project, hollow core mesoporous carbon material was prepared by using silicon-based templates for pore formation and then converting it to carbon. Unique electrocatalyst were obtained by incorporating Pt nanoparticles on this material. Hydrogen oxidation and oxygen reduction activities of the electrocatalysts were determined by using cyclic voltammetry technique. Stability of newly developed materials for fuel cells have been determined by means of in- situ and ex-situ durability tests. Long term stability tests of the newly developed composite membranes and electrocatalysts have been performed according to internationally accepted protocols

A Pt/MnV2O6 nanocomposite for the borohydride oxidation reaction

Problems associated with carbon support corrosion under operating fuel cell conditions require the identification of alternative supports for platinum-based nanosized electrocatalysts. Platinum supported on manganese vanadate (Pt/MnV2O6 ) was prepared by microwave irradiation method and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy. The borohydride oxidation reaction (BOR) on Pt/MnV2O6 was studied in highly alkaline media using voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. BOR electrocatalytic activity of Pt/MnV2O6 was also compared with that of commercial Pt/C (46 wt% Pt) electrocatalyst. The apparent activation energy of BOR at Pt/MnV2O6 was estimated to be 32 kJ mol(-1) and the order of reaction to be 0.51, indicating that borohydride hydrolysis proceeds in parallel with its oxidation. Long-term stability of Pt/MnV2O6 under BOR typical conditions was observed. A laboratory-scale direct borohydride fuel cell assembled with a Pt/MnV2O6 anode reached a specific power of 274 W g(-1). Experimental results on Pt/MnV2O6 were complemented by DFT calculations, which indicated good adherence of Pt to MnV2O6, beneficial for electrocatalyst stability. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved

Electrosprayed catalyst layers based on graphene-carbon black hybrids for the next-generation fuel cell electrodes

Here, we report a novel electrode structure with graphene and graphene–carbon black hybrids by electrospraying for polymer electrolyte membrane fuel cells. After syntheses of platinum (Pt)/partially reduced graphene oxide (rGO) and Pt/r-GO/carbon black (CB) hybrid electrocatalysts, suspensions of synthesized electrocatalyst inks were prepared with Nafion® ionomer and poly(vinylidene fluoride-co-hexafluoropropylene) and electrosprayed over carbon paper to form electrodes. Electrosprayed catalyst layer exhibited uniform and small size Pt distribution. As the graphene content increases micrometer-sized droplet, pore formation and surface roughness of the electrode increase. Thus, an open porous electrode structure which is favorable for mass transport is achieved by electrospraying. The maximum power densities, 324 mW cm−2 for Pt/rGO and 441 mW cm−2 for Pt/rGO/CB electrosprayed electrodes, were achieved at a relatively low catalyst loading