Researchers at the University of Cambridge have developed an innovative technology using artificial leaves that harnesses photosynthesis to convert CO2, water, and sunlight into multicarbon liquid fuels such as ethanol and propanol. The research findings were published in Nature Energy. Unlike fossil fuels, these solar fuels have net zero carbon emissions, are completely renewable, and do not require agricultural land for production. While still at a laboratory scale, this technology could be a game-changer in transitioning away from a fossil fuel-based economy. The artificial leaf directly produces clean ethanol and propanol without the need for intermediary syngas production. This is the first time such complex chemicals have been produced using only solar energy, marking a significant step towards sustainable fuel alternatives.
From simple to complex fuels
Previously, artificial leaves developed by Professor Erwin Reisner and his team in the Yusuf Hamied Department of Chemistry at the University of Cambridge could only produce simple chemicals like syngas, which is used for manufacturing fuels, pharmaceuticals, plastics, and fertilisers. To make the technology more practical and efficient, the researchers aimed to produce more complex chemicals directly in a single solar-powered step.
The breakthrough came in the form of a copper and palladium-based catalyst, which was optimised to enable the artificial leaf to produce more complex chemicals, specifically multicarbon alcohols ethanol and n-propanol. These alcohols are high energy density fuels that can be easily transported and stored, making them valuable in the transition away from fossil fuels.
Achieving net zero emissions
Ethanol is a cleaner alternative to petrol, as it is derived from plants rather than fossil fuels. The majority of cars and trucks today run on petrol containing up to 10% ethanol (E10 fuel). The United States is the world’s largest bioethanol producer, with almost 45% of all corn grown in the country used for ethanol production. However, bioethanol production remains controversial due to its reliance on agricultural land that could otherwise be used for food production.
By using an artificial leaf to produce ethanol and propanol, the researchers have demonstrated the possibility of creating net zero carbon emissions liquid fuels that do not divert agricultural land from food production. This marks a significant step towards a more sustainable and renewable energy landscape.
Optimising the technology
The current artificial leaf device is a proof of concept with modest efficiency. To improve its performance, the researchers are working on optimising the light absorbers for better sunlight absorption and the catalyst for increased conversion of sunlight into fuel. Further work will also be necessary to scale the technology up for mass production and to produce large volumes of fuel.
Despite the challenges, the Cambridge team’s research is a promising development in the quest for sustainable fuel alternatives. As Professor Reisner stated, “Even though there’s still work to be done, we’ve shown what these artificial leaves are capable of doing.” This breakthrough brings us one step closer to harnessing the power of sunlight to generate value-added complex products and ultimately transition away from fossil fuels.