Browsing by Author "Maiyalagan, Thandavarayan"

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    Components for PEM fuel cells: An overview
    (Trans Tech Publications, 2010) Sivakumar, Pasupathi; Maiyalagan, Thandavarayan
    Fuel cells, as devices for direct conversion of the chemical energy of a fuel into electricity by electrochemical reactions, are among the key enabling technologies for the transition to a hydrogen-based economy. Among the various types of fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) are considered to be at the forefront for commercialization for portable and transportation applications because of their high energy conversion efficiency and low pollutant emission. Cost and durability of PEMFCs are the two major challenges that need to be addressed to facilitate their commercialization. The properties of the membrane electrode assembly (MEA) have a direct impact on both cost and durability of a PEMFC. An overview is presented on the key components of the PEMFC MEA. The success of the MEA and thereby PEMFC technology is believed to depend largely on two key materials: the membrane and the electro-catalyst. These two key materials are directly linked to the major challenges faced in PEMFC, namely, the performance, and cost. Concerted efforts are conducted globally for the past couple of decades to address these challenges. This chapter aims to provide the reader an overview of the major research findings to date on the key components of a PEMFC MEA.
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    Effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys
    (Springer, 2012) Valisi, Andiswa; Maiyalagan, Thandavarayan; Khotseng, Lindiwe; Linkov, Vladimir; Pasupathi, Sivakumar
    This work studies the effect of heat treatment of carbon-dispersed platinum and platinum alloys on its methanol tolerance and catalytic activity as gas diffusion electrodes for oxygen reduction reaction (ORR) in acid medium. The catalyst powders were subjected to heat treatments at three different temperatures for a fixed period at controlled atmospheres. Differences in catalyst morphology were characterized using X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscope techniques. The electrochemical characteristics and activity of the electro-catalysts were evaluated for ORR and methanol tolerance using cyclic voltammetry, in the form of gas diffusion electrodes. The optimum heat-treatment temperature is found to be strongly dependent on the individual catalyst. The maximum ORR activity and better methanol tolerance for the oxygen reduction reaction (ORR) was observed in Pt-Fe/C and Pt-Cu/C catalysts subjected to heat treatment at 350 °C.A trend of catalytic activity for oxygen reduction reaction (ORR) was obtained: Pt-Cu/C (350°C)>Pt-Fe/C (350°C) > Pt-Ni/C (350°C) > Pt-Co/C (250°C) > Pt/C (350°C), showing that Pt-Cu/C-type catalysts had a higher catalytic activity with reasonable methanol tolerance.
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    Synthesis and optimisation of IrO2 electrocatalysts by Adams fusion method for solid polymer electrolyte electrolysers
    (Bentham Science Publishers, 2012) Felix, Cecil; Maiyalagan, Thandavarayan; Sivakumar, Pasupathi; Linkov, Vladimir
    IrO2 as an anodic electrocatalyst for the oxygen evolution reaction (OER) in solid polymer electrolyte (SPE) electrolysers was synthesised by adapting the Adams fusion method. Optimisation of the IrO2 electrocatalyst was achieved by varying the synthesis duration (0.5 – 4 hours) and temperature (250 - 500°C). The physical properties of the electrocatalysts were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). Electrochemical characterisation of the electrocatalysts toward the OER was evaluated by chronoamperometry (CA). CA analysis revealed the best electrocatalytic activity towards the OER for IrO2 synthesised for 2 hours at 350oC which displayed a better electrocatalytic activity than the commercial IrO2 electrocatalyst used in this study. XRD and TEM analyses revealed an increase in crystallinity and average particle size with increasing synthesis duration and temperature which accounted for the decreasing electrocatalytic activity. At 250°C the formation of an active IrO2 electrocatalyst was not favoured.
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    Synthesis, characterisation and evaluation of IrO2 based binary metal oxide electrocatalysts for oxygen evolution reaction
    (Electochemical Society Inc., 2012) Felix, Cecil; Maiyalagan, Thandavarayan; Pasupathi, Sivakumar; Bladergroen, Bernard Jan; Linkov, Vladimir
    IrO2, IrxRu1-xO2, IrxSnx-1O2 and IrxTax-1O2 (1 ≥ x ≥ 0.7) were synthesized, characterised and evaluated as electrocatalysts for the oxygen evolution reaction in solid polymer electrolyte electrolysers. The electrocatalysts were synthesised by adapting the Adams fusion method. The physical properties of the electrocatalysts were characterised by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. Electrochemical activity of the electrocatalysts toward the oxygen evolution reaction was evaluated by cyclic voltammetry and chronoamperometry. X-ray diffraction revealed no phase separation when RuO2 or SnO2 was introduced into the IrO2 lattice suggesting that solid solutions were formed. Transmission electron microscope analysis revealed nanosize particles for all synthesised metal oxides. Crystallinity increased with the addition of RuO2 and SnO2 while a suppression of crystal growth was observed with the addition of Ta2O5 to IrO2. Chronoamperometry revealed that the addition of all the secondary metal oxides to IrO2 resulted in improved catalytic performance. Ir0.7Ru0.3O2 was identified as the most promising electrocatalyst for the oxygen evolution reaction. Keywords: