To decrease humankind’s dependence on carbon dioxide-producing fuels, solar energy must be used. The sun shines only intermittently, so technology is needed in order to harvest and store solar energy. Finding a method to efficiently convert sunlight to hydrogen, a chemical fuel that can be stored, is arguably one of science’s most important challenges.
This month, Avner Rothschild and coworkers from Technion-Israel Institute of Technology reported exciting progress in this field. They have used ultrathin (less than 50 nanometres) film made of iron oxide (rust) to improve the efficiency of electrodes in systems that split water into hydrogen and oxygen. Previously used electrodes made of iron oxide were durable and cheap, but inefficient. They were either good absorbers of light or good collectors of the charge produced by the absorbed light, never both. Rothschild’s finding removes the need to sacrifice absorption for collection or vice versa: the researchers use a strategy they call “resonant light trapping” which improves light absorption close to the surface of the material. This absorption causes formation of positive charges, and since the charges produced are so close to the surface, they are quickly collected before dying off. The authors of the report suggest that their strategy can be applied to many other electrode materials in addition to iron oxide, which may lead to cheaper and even more efficient electrodes. A viable system for the storage of solar energy for on-demand use is now one step nearer.
Sources: ScienceDaily and Nature Materials