Oceans are some of the largest carbon sinks on Earth, storing up to thirty-one percent of total carbon dioxide (CO2) emissions. As atmospheric CO2 levels increase, seawater carbon also increases, causing ocean acidification. This is harmful to many marine organisms, especially those that build structures out of calcium carbonate. Researchers in the Hu Lab at Yale’s Department of Chemical and Environmental Engineering recently developed a new mechanism for turning inorganic seawater carbon into fuel, effectively reducing the amount of dissolved carbon in the oceans.
The team tested a new system designed to improve the efficiency of photoelectrochemical (PEC) CO2 reduction devices. These solar-powered devices float on the ocean, utilizing electrodes to extract bicarbonate ions from seawater. The anodic electrode oxidizes water to collect protons, which are transported to the cathodic side. Protons combine with bicarbonate ions along the way, enabling fuel production. Though water oxidation sounds elegant, current PEC devices are often expensive and inefficient, so the Hu Lab’s research is a crucial step forward.
In the study, the team took multiple pairs of photo-electrodes arranged in parallel and placed them into an array, allowing the electrodes to “talk to each other” while the light absorption remained unaffected. This created a seamless carbon conversion cascade, greatly boosting efficiency. “That chemical reactor design allows the electrode itself to behave beyond what a simple, standalone pair could do,” said Shu Hu, a principal investigator on the study. By eventually taking their improved PEC device to the open ocean, the team hopes to mitigate ocean acidification while producing a carbon-neutral fuel alternative, protecting our oceans for future generations.