Mahesh Waje

Polyaniline nanofibre supported platinum nanoelectrocatalysts for direct methanol fuel cells

A novel polyaniline nanofibre supported platinum (Pt) nanoelectrocatalyst is developed for direct methanol fuel cells (DMFCs). Polyaniline nanofibres (PaniNFs) with a 60 nm diameter are synthesized by a scalable interfacial polymerization without the use of a template or functional dopant. PaniNF supported Pt electrocatalyst (Pt/PaniNFs) and carbon black supported Pt electrocatalyst (Pt/C) are prepared by an ethylene glycol (EG) reduction method. The Pt nanoparticles deposited onto PaniNFs have a smaller diameter (1.8 versus 2.3 nm by XRD) and narrower particle size distribution (1.5–3 nm versus 1–5 nm by TEM) than the Pt nanoparticles deposited onto carbon black. The Pt/PaniNFs catalyst shows a higher electrochemical active surface area (ECSA) and higher methanol oxidation reaction (MOR) catalytic activity than the Pt/C.

CNT-Based Electrodes with High Efficiency for PEMFCs

A highly efficient fuel cell electrode structure based on carbon nanotubes (CNTs) is demonstrated. The CNTs were grown on carbon paper by chemical vapor deposition using electrodeposited Co/Ni catalyst. Pt was subsequently deposited by spraying of Pt precursor on CNTs followed by in situ reduction in hydrogen. Cyclic voltammograms show a significant improvement in the Pt utilization in the CNT-based electrode over conventional electrode (58% vs. 34%). Higher membrane electrode assembly performance was observed for CNT-based electrode with a maximum power density of 623 mW cm - 2 at Pt loading of 0.15 mg/cm 2 , 70°C and 3 atm.

Carbon nanotube free-standing membrane of Pt/SWNTs as catalyst layer in hydrogen fuel cells

A simple and promising fuel-cell architecture is demonstrated using a carbon nanotube free-standing membrane (CNTFSM) made from Pt supported on purified single-walled carbon nanotubes (Pt/SWNT), which act as the catalyst layer in a hydrogen proton exchange membrane fuel cell without the need for Nafion in the catalyst layer. The CNTFSM made from Pt/SWNT at a loading of 0.082 mg Pt cm–2 exhibits higher performance with a peak power density of 0.675 W cm–2 in comparison with a commercially available E-TEK electrocatalyst made of Pt supported on XC-72 carbon black, which had a peak power density of 0.395 W cm–2 at a loading of 0.084 mg Pt cm–2 also without Nafion in the catalyst layer.

Effect of Scan Range on Pt Surface Area Loss in Potential Cycling Experiments

Durability of Pt electrocatalyst in PEMFCs is a major obstacle for the successful commercialization of PEMFCs 1 . Pt surface area loss during PEMFC runtime is normally the parameter indicative of the durability of catalyst. There are four mechanisms proposed for Pt surface area loss viz. carbon corrosion, Pt dissolution, Pt dissolution and redeposition and finally migration of Pt on carbon 2 . These mechanisms lead to increased Pt particle size by aggregation and/or ripening. Pt dissolution and carbon corrosion are known to be potential dependent and are normally accelerated at higher potentials. Particularly in the range of open circuit potential (OCP) i.e. about 0.95-1.1 V these two mechanisms are significant sources for Pt electrocatalyst degradation. The aggregation of Pt is found to accelerate under the potential cycling conditions as discussed in the literature. For the automotive applications this is especially important since the operation will require constant change of load as per the drive cycle.

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.