From Science Daily: While its only in the proof of concept stage, researchers at Penn State have developed a device that uses sunlight to split water and produce recoverable hydrogen. Right now its extremely inefficient, but the researcher team thinks they can get up to 10-15 percent efficiency. At higher efficiencies, it’s possible that systems could be developed that could provide a clean source of hydrogen fuel from sunlight and water.
Other research in this area always ran up against the problem that anything you did to make it easier to split apart the water into its hydrogen and oxygen components also made it that much easier for the separated gases to combine again. The Penn State team developed a catalyst system that closely mimics the photosynthesis process and separated the electrodes to avoid the hydrogen recombining. Much more detail on this cell is available at Science Daily.