The Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have created a device that can make use of more sun’s energy. In experiments, the device killed 99.999 percent of bacteria in just 20 minutes. The rectangle device has about half the size of a postage stamp device and looks like nothing but a little piece of black glass. It consists of thin “nanoflake” walls of molybdenum disulfide on a glass surface and each flake is topped with a thin layer of copper. 

Under sunlight, the molybdenum disulfide and copper act as a catalyst, using that sunlight to produce hydrogen peroxide and other disinfectant in the water. When their work was done the killer chemicals quickly dissipated, leaving pure water behind.