Artificial leaf reactor makes ethylene from CO2

BY ANTHONY KING

An artificial leaf reactor powered by sunlight could ultimately convert CO₂ into fuels for cars or planes, say researchers. For now, their lab-scale device made ethane and ethylene by combining a photo absorber with a special copper electrocatalyst (Nature Catalysis, DOI: 10.1038/s41929-025-01292-y). Ethylene (C₂H₄) is a crucial feedstock for industrial plastic production.

‘It is quite challenging to produce hydrocarbons like ethylene or ethene because typically your photoabsorber does not produce enough voltage,’ says Virgil Andrei at the University of Cambridge, UK, who visited the Berkeley lab of Peidong Yang for this research. ‘To achieve this, we developed a copper nanoflower catalyst, which requires less voltage to produce these products.’

The device had two light absorbers. First, a bismuth vanadate can capture the blue wavelengths of sunlight to oxidise water to oxygen. Then a second light absorber – lead halide perovskite – captures the remaining photons to reduce CO₂ to different products with the help of the copper catalyst.

The copper nanoflower can catalyse CO₂ and its intermediate species to steer the selectivity towards complex hydrocarbons. ‘This special copper catalyst allowed us to directly make products which have a higher energy density,’ says Andrei. These were higher value compounds such as ethylene.

In the new device, the oxygen evolution reaction was replaced by glycerol oxidation, which was achieved by coupling the photocathodes to silicon-nanowire photoanodes. This allowed glycerol to be oxidised to the compounds acetate, glycerate and lactate, value-added chemicals useful in the pharmaceutical, food and cosmetic industries.

This is a proof-of-concept demonstration ‘for simultaneous multicarbon synthesis and biomass-derived waste conversion into value-added products,’ the study states. ‘None of the separate aspects are really very new, but the breakthrough is that it is a smart combination,’ says Jennifer Strunk, a catalyst chemist at the Technical University of Munich in Germany.

‘Lots of studies optimise either reduction or oxidation side of things. Here they optimise both and put it all together in one working device that can go from light and CO₂ to C₂ chemicals,’ she adds. Also, ‘most processes nowadays have a low efficiency in making oxygen, but here they circumvent this step by oxidising glycerol,’ says Strunk.

Andrei says: ‘We still need to make more progress on stability, scalability and ease of manufacturing to move the process towards commercialisation’. Some technology and knowledge could be taken from solar cell manufacturing, but they would need to be adapted for solar fuel production.

‘This is a nice system but the conversion efficiency needs to be much improved,’ Strunk adds, with the paper reporting total hydrocarbon selectivity at around 0.2%. ‘In solar cells, we convert approximately 20% of light [to electricity]. Here, less than 1% of the light is actually converted to chemicals.