Concentrated photosynthesis device promises cheap green hydrogen

We are a solar-powered planet; the vast majority of energy needed for life on Earth comes from the sun – and a lot of it, including food and fossil fuels, is the result of plant-based photosynthesis – the conversion of sunlight, water and carbon dioxide into oxygen and sugars. The first chemical step in photosynthesis happens in the chlorophyll that gives leaves their green color – and this step is effectively a water-splitting operation that breaks H₂O into oxygen, which is released into the air (thanks, plants), and positively charged hydrogen ions, which drive the remainder of the process and eventually allow plants to store energy in carbohydrate form.

Evolution has delivered an extraordinary gift in photosynthesis, and as humanity works to free itself from the harmful side-effects of fossil fuels, researchers are working to replicate, and even improve on, this first step, hoping to develop artificial photosynthesis techniques that some predict will eventually be the cheapest way to produce green hydrogen, for use as an energy storage medium.

“In the end, we believe that artificial photosynthesis devices will be much more efficient than natural photosynthesis, which will provide a path toward carbon neutrality,” says Zetian Mi, a University of Michigan professor in electrical and computer engineering.

Mi and his team have just published a paper in Natureon what they consider to be a major leap in artificial photosynthesis. The team has demonstrated a new photocatalytic water-splitting semiconductor that harnesses a broad spectrum of sunlight, including the infrared spectrum, to split water at a solid 9% efficiency – nearly a tenfold improvement from other devices of its kind – and it's a tiny and relatively affordable device that improves rather than degrades over time.

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