Artificial leaves: Bionic photosynthesis as good as the real thing

Converting sunlight into liquid fuel through artificial photosynthesis would be a huge environmental victory – and the latest prototypes look surprisingly effective

By Katharine Sanderson

Our insatiable appetite for energy has got us into a mess, with the burning of fossil fuels releasing greenhouse gases that are heating the atmosphere. It is enough to make you envious of plants, which produce their own energy – through photosynthesis – in a way that actually uses up the greenhouse gas carbon dioxide. If we could learn to mimic this trick on a grand scale, it would enable us to effectively liquefy sunlight to create a clean, green fuel.

Unfortunately, photosynthesis is a tough chemical reaction to copy. It involves many processes, including capturing sunlight, splitting apart water molecules to yield protons, and joining these protons with carbon atoms from CO₂ to ultimately produce fuel in the form of sugars. In nature, these jobs are performed by proteins that have had hundreds of millions of years to evolve – and they still only manage to turn energy from sunlight into fuel with an efficiency of 1 per cent at best.

A decade ago, chemist Daniel Nocera at Harvard University made a big stride forwards when he developed catalysts based on nickel and cobalt that could break apart water. That is just one part of recreating photosynthesis, however, and progress has since stuttered.

Then people started to realise that instead of recreating photosynthesis from scratch, we could combine the best bits of chemistry and biology in a bionic leaf. Such leaves typically employ materials that efficiently absorb sunlight as well as natural proteins that excel at stitching together fuel molecules. A team led by Erwin Reisner at the University of Cambridge recently used a material called a perovskite …