Designer catalyst with enzyme-like cavity splits water almost as fast as plants

Using molecular design, researchers have developed a synthetic water oxidation catalyst with an enzyme-like cavity to speed up the reaction. This unusual catalytic system achieves the challenging oxidative water-splitting reaction at a comparable rate to the photosystems found in photosynthesis.

Water oxidation is a key step in photosynthesis and involves splitting two water molecules into molecular oxygen and protons using solar energy. While this process is crucial in nature to sustain life, the ability to cheaply reproduce this reaction could help meet humanity’s energy needs by creating a steady stream of oxygen and hydrogen. Synthetic mimics of the natural oxygen evolving complex are known, but generally suffer from low catalytic activity or short lifetimes. ‘It is very hard to oxidise water,’ explains Stefan Bernhard, a renewable energy chemist at Carnegie Mellon University, US. ‘The process requires the transfer of four electrons and so needs a lot of electrochemical or photochemical energy. One of the particularly tricky aspects is ensuring that the catalyst isn’t just “burnt up” by these demanding conditions.’