For the first time, researchers have designed an electrochemical cell that can desalinate seawater (Nano Lett., DOI: 10.1021/nl203889e). A team led by Fabio La Mantia of Ruhr University in Bochum, Germany, thinks the battery’s cost and efficiency could eventually improve on standard seawater purification techniques, which require heaters or high-pressure pumps. The new system draws ions from seawater into a pair of electrodes. As the researchers pass current through the electrodes, electrochemical reactions drive chloride ions to a silver electrode and sodium ions to an electrode made from manganese oxide nanorods. Next, the researchers remove the desalinated water and release the trapped ions into a waste stream of seawater by reversing the direction of the electrical current. The desalination battery reverses the idea behind a project to create new sources of clean energy. Last year, La Mantia, Yi Cui of Stanford University, and other team members showed that they could generate electrical energy by flowing streams of water with varying salinity through an electrochemical cell (Nano Lett., DOI: 10.1021/nl200500s). The desalinated water that comes from the battery still contains too much salt for drinking, La Mantia says, but he plans to improve the device’s performance.