Continuous electrochemical water splitting from natural water sources via forward osmosis.

Electrochemical water splitting stores energy as equivalents of hydrogen and oxygen and presents a potential route to the scalable storage of renewable energy. Widespread implementation of such energy storage, however, will be facilitated by abundant and accessible sources of water. We describe herein a means of utilizing impure water sources (e.g., saltwater) for electrochemical water splitting by leveraging forward osmosis. A concentration gradient induces the flow of water from an impure water source into a more concentrated designed electrolyte. This concentration gradient may subsequently be maintained by water splitting, where rates of water influx (i.e., forward osmosis) and effective outflux (i.e., water splitting) are balanced. This approach of coupling forward osmosis to water splitting allows for the use of impure and natural sources without pretreatment and with minimal losses in energy efficiency.