Semiconductor-based ‘artificial plant’ turns CO2 into fuel

For decades, scientists have been endeavoring to mimic plants’ ability to turn the energy of light, water and CO₂ into fuels. But whereas plants make sugars, which are sizable and complex molecules, researchers are happy with simple hydrocarbon compounds. Even linking together just two carbon (C) atoms from two CO₂ molecules makes for useful products that can be fed into chemical plants to be turned into fuels or plastics.

Researchers at the University of Michigan have done just that. Their artificial photosynthesis system based on a semiconductor surpasses previous attempts by a significant margin in terms of efficiency, yield and longevity. Moreover, the device functions under realistic circumstances: submerged in CO₂-enriched water while being exposed to light equivalent to the sun at noon.

From afar, the underlying chemical transformation boils down to splitting water into hydrogen and oxygen gas, stripping oxygen atoms from CO₂ and reshuffling the intermediates to ethylene (C₂H₄) gas. The water-splitting part falls to gallium nitride (GaN) nanowires, which capture light to provide the energy needed for this chemical reaction as well as the hydrogen (H) that ends up in ethylene. The carbon-linking part happens on tiny copper clusters that dot the nanowires. These capture and partially disassemble CO₂ before adding hydrogen.