The artificial leaf contains a pair of solar cells that power an infinitely more complex version of the electrolysis you learned about in high school science. Energy from the sun is used to catalyze a reaction with various obscure compounds like nanoflake tungsten diselenide (which is a transition metal dichalcogenide). Synthetic gas comes out of the other side, which can either be used directly by vehicles that can take it, or converted further into diesel.
But this isn't the first time we've seen artificial photosynthesis being used as a potential weapon in the war on climate change. Early last year, we saw a team from Berkeley using a similar process, albeit with genetically-modified E. coli bacteria at the heart of the system. That version didn't output synthetic gas but acetate, a building block of several compounds like biofuel, anti-malaria drugs and biodegradable plastics.
Should UIC's newer process prove to be cost-effective, it could spell the end of traditional gasoline production as we know it. Instead, a network of these cells would be installed at a solar farm, creating fuel and reducing the quantity of atmospheric carbon dioxide at the same time. The only downside is that we'd still be re-releasing the deadly gas back into the atmosphere, but it's a decent stop-gap while we work on reducing our carbon emissions more permanently.