A device made from commonly used oxide and carbon-based materials can produce pure hydrogen from water within weeks, according to a study. The discovery could help overcome one of the main challenges in solar fuel production: the currently abundant light-absorbing materials on Earth are limited in performance or stability. The transition to full decarbonisation and the UK’s target of net-zero emissions by 2050 will rely heavily on hydrogen fuel. Since most hydrogen is currently produced using fossil fuels, scientists are now trying to develop more environmentally friendly hydrogen production methods.
Building devices that capture sunlight and split water to produce green hydrogen is one way to achieve this. Although many light-absorbing materials for green hydrogen production have been explored, most of them decompose rapidly when immersed in water.
For example, the most efficient light-harvesting materials are perovskites, which are unstable in water and contain lead. Scientists have been working hard to develop lead-free alternatives because of the risk of leakage.
Bismuth oxyiodide (BiOI) is one such alternative. So far, it has been neglected as a nontoxic semiconductor option for solar fuel applications due to its low water stability. But based on previous studies of the material’s potential, the researchers chose to choose BiOI to make green hydrogen.
The results of the study were published in Nature Materials.
Researchers have created devices that mimic the natural photosynthesis process of plant leaves. Made of BiOI and other eco-friendly materials, these artificial leaf devices absorb sunlight and generate O2, H2 and CO.
The researchers were able to improve the stability of these artificial leaf devices by sandwiching BiOI between two oxide layers. To prevent moisture infiltration, a water-repellent graphite paste is applied to the strong oxide-based device structure. As a result, the stability of BiOI’s light-absorbing pixels increased from minutes to months.
This is a major discovery that elevates BiOI to the status of a viable light collector capable of producing stable green hydrogen.
Dr Virgil Andrei, a researcher at St John’s College, University of Cambridge, and scientists at Imperial College London, who led the study, said that even if some pixels were incorrect, they were able to separate them so that they had no t to affect the remainder. This means that researchers can maintain the performance of small pixels over a larger area.
These findings suggest that these novel devices have the potential to outperform conventional light absorbers. The new method to improve the stability of the BiOI artificial leaf device can now be applied to other unique systems, facilitating their commercialization.