Photoelectrochemical curiosity piqued? You can check out this short video from the EPFL folks.
The (Rusty) Nitty-gritty
So now that we've determined that -- yes -- we can store solar energy in rust and water, we should probably back up a little bit and explain more about how scientists in Switzerland actually made that happen.
As we said, the device contains an oxide semiconductor and a dye-sensitized solar cell. The oxygen evolution (the process of getting molecular oxygen from a chemical reaction) happens on the rust photo anode (where the current flows in) and the hydrogen evolution happens on the cathode side of the device (where the current flows out). When those reactions occur, the electrons are trapped in the dye-sensitized cell where they create a charge, and the hydrogen can be extracted from water. And voila -- energy is stored.
But as we said, the price, not the process, has long posed the biggest challenge. Instead of using a fancy semiconductor (which initiates the oxygen evolution), the team settled on cheap, easy-to-find rust. Unfortunately, rust also happens to be a pretty terrible semiconductor. Researchers at Israel Institute of Technology (Technion) are also attempting to solve this problem, by creating an ultrathin layer of rust in a solar cell that combines more efficient semiconductor silicon [source: Focus]. Likewise, the rust EPFL researchers use is actually designer iron oxide, with silicon oxide added to it, then painted with a layer of aluminum and cobalt oxide that improve the reaction performance.
This means that scientists have found a way to produce electricity and hydrogen that can be stored for use whenever -- not just when the sun is shining.
Pretty cool, huh? Ponder that while you're mowing the lawn and chugging diet soda.