The ocean plays a vital role in regulating Earth’s climate by acting as the planet’s largest active carbon sink, taking in about 400 million tons of carbon dioxide (CO₂) from the atmosphere every year. Now, a team of researchers at Yale has developed an innovative system that captures this dissolved CO₂ from seawater and converts it into clean fuels and valuable industrial materials. Their work, published in Nature Communications, offers a new way to tap into the ocean as a sustainable source for carbon-based products—while also helping to maintain healthier CO₂ levels in the water.
The project was led by Professor Shu Hu of Yale’s Department of Chemical and Environmental Engineering and the Yale Energy Sciences Institute. He describes the system as a “solar-driven, ocean-based carbon capture and conversion” process—or in simpler terms, using sunlight to make fuel. The technology harnesses solar energy to convert the CO₂ in seawater into syngas, a mixture of carbon monoxide (CO) and hydrogen. This gas is an essential ingredient in producing a wide range of industrial chemicals and clean energy sources.
Past attempts to use solar energy to turn the carbon dissolved in seawater into useful products have run into major obstacles. One of the biggest issues is that seawater contains very low levels of carbonate ions, which makes it hard to achieve both high energy efficiency and precise control over what products are formed. On top of that, most current reactor designs are limited to small-scale lab experiments. To make real progress, it’s not just about finding the right catalysts—there also needs to be a reactor that can run continuously and handle large volumes to fully tap into seawater as a carbon source.
Building on their expertise in photocatalysis and reactor design, the Hu group at Yale has created a new photoelectrochemical device that uses only sunlight to convert dissolved carbon in seawater—mainly in the form of bicarbonate—into syngas. This process mimics natural photosynthesis in marine ecosystems and achieves a solar-to-fuel efficiency of 0.71%, which is comparable to the carbon conversion efficiency of seaweed.
READ ALSO: The Hutchinson site in Château-Gontier has earned the AeroExcellence Bronze certification.
READ ALSO: Float like a jellyfish: New coral mobility mechanisms uncovered
One of the most surprising findings from the team was how strongly the reactor’s internal flow design influenced the outcome of the reaction. Although seawater contains almost no carbonate ions, the flow conditions within the reactor significantly boosted the production of carbon monoxide (CO). In still seawater, CO made up just 3% of the product, but under carefully controlled flow, that number jumped to 21%, showing how important reactor design is for improving efficiency and selectivity.
“It’s like a perfectly timed relay race,” said Xiang Shi, a co-author of the study and graduate student in Professor Hu’s lab. “The anode hands off protons and CO₂ to the cathode, which takes it from there and completes the conversion. This smooth handoff is what makes the whole process run so efficiently.”
The team achieved this by designing the reactor so that the flow of seawater first moves through the anodes, where water is oxidized and protons are released. These protons are then carried along by the flow, triggering a chain of reactions that convert bicarbonate into dissolved CO₂. That CO₂ is then delivered downstream to the cathodes, where it’s turned into fuel.
READ ALSO: NIST and Partners Harness Quantum Physics to Create Random Number Generator Factory
By carefully controlling how materials move within the reactor, the team was able to manage the reaction process at the electrode surface. This allowed them not only to extract CO₂ from seawater but also to harness sunlight to turn it into usable fuel—directly from the ocean.
The researchers’ next goal is to refine the system and eventually scale it up into a full-sized, industrial reactor. Thanks to its modular design, the reactor can be expanded by assembling multiple flow cells into square-meter-sized floating platforms. These floating units are designed to use natural ocean movements—like tides and currents—to keep seawater flowing through the system without the need for pumps. As the seawater moves through the reactors, sunlight powers the continuous conversion of dissolved CO₂ into syngas, which can then be collected and sent to industrial plants for use in making chemicals or fuels.
“Our vision is to deploy large floating reactors at sea, where we can tap directly into sunlight and seawater to produce solar fuels,” Hu explained.
