The system is made up of a perovskite solar cell, hooked up to electrodes made of a catalyst that electrolyzes the water. When sunlight hits the solar cell, it produces electricity that powers the catalyst, which then splits the water into oxygen and hydrogen. These bubble up to the surface where they can be collected for use.

The sunlight-to-hydrogen efficiency sits at around 6.7 percent, which is relatively high for these types of systems. But the most useful feature, the team says, is just how self-contained the new design is. The solar cell and the electrodes are all in one unit – the solar cell components are encased inside a polymer shell that protects them from water damage while still letting sunlight through. The electrodes sit on the outside where they can split the water.