A multidisciplinary team of scientists from China, Hong Kong, the USA, and Saudi Arabia is the first to successfully harvest energy from sea waves to produce a carbon-based liquid fuel. Their prototype system can convert carbon dioxide into hydrogen-carrier formic acid solely by generating static electricity from the undulating motion of the water. The research has been published in Energy Environ.
Siu-Fung Leung, from Saudi Arabia’s King Abdullah University of Science and Technology, said:
“We realized that we needed different types of expertise to contribute to this project. Expertise in nanogenerators, in electrocatalysis, and also in electronic circuits.”
How It Works
- The method works with triboelectric nanogenerators – which are floating spheres that embody a concertina-like structure.
- The concertina folds rub together when the spheres bob on the water waves. The motion generates static electricity, similar to rubbing a balloon on clothing.
- In principle, an electrochemical cell could be driven by this electrical energy to convert carbon dioxide to formic acid. However, the voltage generated by the triboelectric nanogenerators is too unpredictable. As a solution, the team added: a supercapacitor and a system of rectifiers as an intermediary component. They accumulate the generated charge and release it to the cell in a controlled and steady manner.
System Components
- A spring-assisted spherical triboelectric nanogenerator.
- An energy storage circuit with rectifiers and a supercapacitor.
- A two-electrode electrochemical cell for the carbon dioxide reduction and oxygen evolution reactions.
Katherine Holt, an electrochemistry expert at University College London, UK, said:
“They are the first to think about how you would integrate the two of these technologies together. It’s going from fundamental lab-based research to demonstrating on a small scale that this is feasible.”
There are indeed significant potential benefits in turning an intermittent renewable energy source into a stored chemical form. However, Holt admits there is a missing ingredient:
“Where’s the carbon dioxide coming from? If I just leave a solution open to the air, some carbon dioxide will dissolve in, but the concentration will be quite low.”
Leung agrees with Holt that low carbon dioxide concentration is a hurdle. He said:
“The entire field is facing this challenge. A lot of people in the field of carbon dioxide reduction are working on it.”
A potential solution to this problem would be to source concentrated CO2 from the emissions of an industrial process, such as a factory or power plant. However, how the captured carbon dioxide could be fed into an ocean-borne array of generators remains a question.
