Artificial photosynthesis device improves its own efficiency over time

Scientists have carried out a research that demonstrates a new form of technology that can replicate the natural process of photosynthesis as it also experiences morphological changes during use to improve performance.

The demonstration using an artificial photosynthesis device showed that the device reproduced the process to generate clean hydrogen fuel, reports New Atlas.

Scientists from  University of Michigan (UM) and Lawrence Livermore National Laboratory were experimenting with an artificial photosynthesis system that UM engineer Zetian Mi had previously created.

By harnessing sunlight to break fresh and salt water and produce hydrogen for use in fuel cells, the system promised a cleaner method of hydrogen production, which usually involves using natural gas or electrical energy.

By harnessing sunlight to break fresh and salt water and produce hydrogen for use in fuel cells, the system promised a cleaner method of hydrogen production, which usually involves using natural gas or electrical energy.

The unit, which was made of silicon and gallium nitride, common materials in electronics and solar cells, had a three-percent solar-to-hydrogen performance, compared to the one-percent efficiency provided by previous devices.

It achieved this through a "cityscape" of gallium nitride towers on a silicon backing that turned sunlight into free electrons, which in turn split the water into hydrogen and oxygen.

These results were published back in 2018, but the scientists have continued studying the device to better understand the reasons behind its superior efficiency. 

In the latest study, the team used a range of advanced microscopy and spectroscopy techniques to observe the materials in action, and uncovered some surprises.

While an artificial photosynthesis device would normally be expected to decline in performance in a matter of hours as the materials wear out, this one actually grew more efficient over time. 

The scientists' observations revealed that as the system was used, the very tops of the gallium nitride towers formed new sites for hydrogen production by absorbing oxygen and taking on new properties, becoming a material known as gallium oxynitride.

"We discovered an unusual property in the material that enables it to become more efficient and stable," says Francesca Toma, senior author of the paper. "Our discovery is a real game-changer. I've never seen such stability."

For their next steps, the scientists will experiment with the material as part of a complete photoelectrochemical cell for splitting water, which will include exploring how similar materials might make these systems even more stable.

"The collaboration helped to identify the fundamental mechanisms behind why this material gets more robust and efficient instead of degrading," says Mi. "The findings from this work will help us design and build more efficient artificial photosynthesis devices at a lower cost."

The research was published in the journal Nature Materials.