Provided are compositions for and methods of producing hydrogen. For example, the compositions comprise nanocrystals, a catalyst, a source of electrons, and an aqueous medium. The nanocrystals, catalyst, aqueous medium, and, optionally, the source of electrons are present as a mixture. The methods produce hydrogen by exposing the compositions to electromagnetic radiation (e.g., solar flux).
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with government support under Grant No. DE-FG02-09ER16121 awarded by the U.S. Department of Energy. The government has certain rights in the invention.