Transmission Electron Micrograph of graphene decorated with nanoparticles. The dark spots represent the platinum nanoparticles, while the grey sheet is the graphene support material. (Image Credit: Patrick Cullen / Gyen Ming Angel)
Researchers at Queen Mary University of London and University College London (UCL) have come up with a new design for hydrogen fuel cell catalysts using graphene. They demonstrated that this graphene-based catalyst was more durable than other catalysts while matching their performance. The team published their findings in the journal Nanoscale.
Hydrogen fuel cells transform chemical energy into electrical energy by mixing hydrogen and oxygen with the help of catalysts. Since this method produces water, it provides a clean and renewable power source.
Platinum is the most common catalyst that's used for these fuel cells. However, it's very costly, which poses a problem for the commercialization of hydrogen fuel cells. To overcome the issue, catalysts were created by decorating small nanoparticles of platinum on a cheaper carbon support. However, it's not very durable, and that alone reduces the lifetime of today's fuel cells.
According to previous research, graphene leads the way when it comes to using an ideal support material for fuel cells. This is mainly due to its corrosion resistance, high surface area and high conductivity. However, the graphene used in many of these experiments suffered from high defect concentrations emerging from a non-uniform coverage of nanoparticles, which can degrade performance.
The team came up with a new technique, which involves creating high-quality graphene coated with platinum nanoparticles in a one-pot synthesis. According to the team, these particles are of the optimal dimensions to be uniformly dispersed across a surface.
"Satisfying global energy demands without damaging the environment is one of the great modern challenges. Hydrogen fuel cells can provide cleaner energy and are already used in some cars as an alternative to petrol or diesel. However, a big barrier to their widespread commercialization is the ability for catalysts to withstand the extensive cycling required for their use in energy applications. We've shown that by using graphene instead of the typical amorphous carbon as a support material, we can create ultra-durable catalysts." said Dan Brett, Professor of Electrochemical Engineering at UCL.
Using accelerated stress tests as recommended by the US Department of Energy, the team discovered that the graphene-based catalyst is more durable than commercial ones. It provided higher stability over an operating lifetime of 30,000 charge/recharge cycles. The team also demonstrated that the loss in activity over the same testing period was around 30% in the new graphene catalyst.
Furthermore, the newly-developed graphene matches the performance of highly-optimized platinum/carbon catalysts. Plus, it's more stable. This is the first time ever that uniformly sized platinum nanoparticles have been grown on graphene support with low defects. The team believes that this technique, along with the synthesis of charged graphene dispersion using the "metal-ammonia" method, makes the technology scalable.
What's even more exciting about this synthesis technique is that it can be turned to spread different metals across a graphene structure. This can then be utilized on different applications, including sensors and supercapacitors.
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