Plants do it right. They’ve evolved to use the sun as their main energy source, converting solar energy into chemical energy in a process known as photosynthesis. The result, finely honed over billions of years, is a fast, efficient system that splits water (H2O) up into its component parts. Such a method would be the ideal clean-energy technology, using the sun’s rays to convert water into oxygen and hydrogen, the cleanest natural gas. Scientists have been trying to mimic the system for decades, but they always fell short. It was nearly impossible to split water fast enough for the process to be efficient.
Now, a group of researchers at the Royal Institute of Technology in Stockholm, Sweden, has developed a method that, for the first time, approaches speeds that approximate nature’s own process. The sticking point has always been finding the right catalyst, a molecule that could speed up the chemical reaction in just the right way.
"Splitting water into hydrogen and oxygen isn’t easy—it needs high energy," says Licheng Sun, the organic chemist who led the research. The chemical reactions that are required need chemical prompting, and the catalysts that had been created just weren’t efficient enough. "The reported catalysts are too slow. Two hundred orders of magnitude slower than nature, and they couldn’t speed up the process enough for efficient splitting."
Sun and his colleagues developed a catalyst that, at least when put into solution, split water at close to the same pace as that found in grass and leaves. They’re now working to integrate it into a device that can be commercialized. "I have been working in the field for more than 20 years, and on this catalyst for five years," Sun says. "This can replace fossil fuels. We don’t need coal, petroleum, or natural gas. We’re only keeping them for energy. But we can use sunlight to drive the whole world."