Abstract
In this research, the activity and stability for methanol electro-oxidation on Pt-Ru/C catalysts was increased by optimising the catalyst preparation method. The Pt-Ru/C catalysts were synthesised using Pt(acac)2 and Ru(acac)3 precursors for chemical deposition of the metals. Performance of the catalyst was examined by cyclic voltammetry and chronoamperometry in a methanol-containing electrolyte. TEM, EDS, X-ray photoelectron spectroscopy and XRD were used to physically characterise the catalysts. The parameters investigated were precursor decomposition phase, synthesis temperature and Pt/Ru ratio. Precursor deposition from the liquid phase was more active for methanol electro-oxidation, predominantly due to particle size and degree of alloying achieved during this precursor decomposition phase. Synthesis temperature affected the particle size, active surface area, ruthenium oxidation state and degree of alloying which in turn affected catalyst stability and activity for methanol electro-oxidation. The Pt/Ru ratio greatly affects the performance of the catalyst. The catalyst with the highest activity for methanol electro-oxidation was the catalyst synthesised at 350 °C with a Pt/Ru ratio of 50:50.Graphical
Highlights
Methanol is considered to be the most promising alcohol for portable and microfuel cell applications since methanol is a liquid under atmospheric conditions, synthesised and inexpensively, with a specific energy density of 6 kWh kg−1 [1]
The results show that the catalyst prepared in a vacuum atmosphere has a larger electrochemically active surface area (ECSA), which is expected due to the smaller particles as seen in Transmission Electron Microscope (TEM) and confirmed by X-ray Diffraction (XRD) crystallite size
This study involved the systematic investigation of operating atmosphere, temperature and Pt/Ru ratio in catalyst preparation by organo-metallic chemical deposition
Summary
Methanol is considered to be the most promising alcohol for portable and microfuel cell applications since methanol is a liquid under atmospheric conditions, synthesised and inexpensively, with a specific energy density of 6 kWh kg−1 [1]. The direct methanol fuel cell (DMFC) is a promising alternative to conventional batteries, as they offer longer run times and methanol can be replenished from the fuel storage. This would translate into a longer battery life and more power available on portable devices. Despite the many advantages of DMFC’s over hydrogen polymer electrolyte fuel cells (PEFC’s), the drawbacks of DMFC’s are the high cost of materials used in fabrication, the crossover of methanol from the anode to the cathode, ruthenium dissolution and crossover from the anode to the cathode, low efficiency and low power density [2]. The high catalyst loading increases mass transfer limitations which further decreases the efficiency at the anode [3]
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