Engineers at MIT have designed an electrode that boosts the efficiency of electrochemical reactions used to turn carbon dioxide into ethylene. This electrode could also be used to produce high-value chemicals such as methane, methanol and carbon monoxide.
The performance of gas diffusion electrode materials is a trade-off between conductivity and hydrophobicity. While good electrical conductors are needed to drive the process, they also must prevent water-based electrolyte solutions from leaking through and affecting reactions at the electrode surface. However, increasing one reduces the other.
The MIT solution uses a very thin sheet of highly hydrophobic but poorly conducting plastic PTFE through which a series of conductive copper wires are woven.
Because the copper wire is more conductive than the PTFE material, it acts as a superhighway for electrons passing through, bridging the areas where they are confined to the substrate and face greater resistance.
In effect, by weaving the wire through the material, the material is divided into smaller subsections determined by the spacing of the wires.
“We split it into a bunch of little subsegments, each of which is effectively a smaller electrode,” explained Simon Rufer, a doctoral student in MIT’s department of engineering and co-author of a paper describing the work in a recent Nature Communications.
The engineers have dubbed their new architecture a hierarchically conductive gas diffusion electrode (HCGDE).
Aiming to demonstrate the potential for scaling up their system, the researchers produced a 50cm2 sheet for testing.
To demonstrate that the system is robust, they ran a test electrode for 75 hours continuously, with little change in performance.
Overall, Rufer says, their system is the first PTFE-based electrode that has gone beyond the lab scale of 5 cm or smaller. “It’s the first work that has progressed into a much larger scale and has done so without sacrificing efficiency,” he emphasized.
The weaving process for incorporating the wire can be easily integrated into existing manufacturing processes, even in a large-scale roll-to-roll process, he added.
“Our approach is very powerful because it doesn’t have anything to do with the actual catalyst being used,” Rufer said. “You can sew this micrometric copper wire into any gas diffusion electrode you want, independent of catalyst morphology or chemistry. So, this approach can be used to scale anybody’s electrode.”
Shell supported the work through the MIT Energy Initiative, which promotes research and development in high-value, sustainable technologies.
