Using solar energy to split water into its component parts, thereby allowing the solar energy to be stored as hydrogen fuel, generally involves one of two methods: using photoelectrochemical cells to directly split the water, or using solar cells to produce electricity to power an electrolyzer that separates the water molecules. One problem associated with the latter method is that it currently relies on rare metals. But now scientists from Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have managed to do so using common materials, and have achieved a record solar energy to hydrogen conversion efficiency in the process.

In addition to the nickel and iron catalysts used for the electrodes in their electrolyzer, the researchers are using solar absorbers made of perovskite – another abundant material – in the solar cells. Perovskite has been generating interest in recent years for its use in different kinds of solar cells as well as in solar water splitting.

The material, which could be a cheaper alternative to the silicon more generally used in photovoltaic cells, is not a new discovery, having been first found in the Ural mountains in 1839. Originally only the oxide mineral itself was called perovskite but the name now takes in other elements with the same crystalline structure and is often found in items as workaday as car batteries.