Toyota rolls out world s first mass market fuel-cell car
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Fuel cells are devices that generate electricity by means of a chemical reaction that does not involve combustion. They can be employed in a variety of scales and situations — from powering portable electronic devices up to vehicles and even whole buildings. The most common fuel used is hydrogen, which results in a highly efficient cell that does not produce any greenhouse gases as a result of its operation. However, most of this element is sourced from natural gas and other fossil fuels, and so its extraction adds to both the cost and environmental impact of hydrogen fuel cells. The hydrogen used in fuel cells is also stored as a compressed gas, which inherently makes containment and transport of the fuel a challenge.
In their study, physicist Professor Apparao Rao of the Clemson Nanomaterials Institute (CNI) in South Carolina and his colleagues have turned their attention to the potential to replace hydrogen fuel cells with those powered by ethanol.
Ethanol is an alcohol commonly derived from corn, barley, sugar cane and other agricultural-based feedstocks.
Unlike hydrogen, it exists as a liquid at ambient conditions, making it far easier and safer to store and transport, but it comes with its own particular set of hurdles to overcome, in particular around the choice of the fuel cell’s anode, there ethanol is oxidised to produce electricity and water as a by-product.
Process engineer Dr Lakshman Ventrapragada, formerly of the CNI, explained: “To make it a commercial product where we can fill our tanks with ethanol, the electrodes have to be highly efficient.
“At the same time, we don’t want very expensive electrodes or synthetic polymeric substrates that are not eco-friendly because that defeats the whole purpose.
“We wanted to look at something green for the fuel cell generation process and making the fuel cell itself.”
Many fuel cell designs rely on platinum as a catalyst, but this metal is costly and can be rendered inert by reaction intermediates like carbon monoxide.
Instead, the researchers looked to use gold nanoparticles. On their own, these particles agglomerate, reducing the available surface area for the energy-producing reaction and therefore lowering their efficiency.
However, this can be avoided when the nanoparticles are stabilised by a porous network of curcumin — a bright yellow chemical found in turmeric.
Furthermore, the team found that the gold–turmeric mix could be deposited on the surface of a fuel cell’s electrode at a current 100 times lower than with previously tested alternatives.
Professor Rao said: “Of all the catalysts for alcohol oxidation in alkaline medium, the one we prepared is the best so far.”
Professor Rao added: “Without this curcumin coating, the performance is poor.
“We need this coating to stabilise and create a porous environment around the nanoparticles, and then they do a super job with alcohol oxidation.
“There’s a big push in the industry for alcohol oxidation. This discovery is an excellent enabler for that.
“The next step is to scale the process up and work with an industrial collaborator who can actually make the fuel cells and build stacks of fuel cells for the real application.”
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According to Dr Ventrapragada, their findings may have implications beyond that of fuel cells — with potential applications in the development of sensors, supercapacitors and beyond.
Dr Ventrapragada added: “In the beginning stages of the project, we did not imagine other applications that gold-coated curcumin could support.
“However, before the end of the alcohol oxidation experiments, we were fairly confident that other applications are possible.
“Although we don’t have a complete understanding of what’s happening at the atomic level, we know for sure that curcumin is stabilising the gold nanoparticles in a way that it can lend itself to other applications.”
One application already being explored by Professor Rao’s team is a sensor that could help detect changes in levels of the neurotransmitter dopamine, which has been implicated in conditions such as Parkinson’s disease and attention deficit hyperactivity disorder.
Preliminary results have indicated that their sensor design can be used to accurately measure dopamine levels in urine samples more cheaply than existing approaches.
The full findings of the study were published in the journal Nano Energy.
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