Solar Pixels Abundant On Earth Found To Produce Hydrogen For Weeks, Says Study

According to a study, devices made of commonly available oxide and carbon-based materials can manufacture pure hydrogen from water for weeks. The discovery could aid in overcoming one of the major challenges in solar fuel production: present earth-abundant light-absorbing materials are limited in terms of performance or stability. The move to full decarbonisation and the UK's target of net-zero emissions by 2050 will rely heavily on hydrogen fuel. Because the majority of hydrogen is currently produced using fossil fuels, scientists are now attempting to develop more environmentally friendly methods of producing hydrogen.

Making devices that can capture sunlight and split water to produce green hydrogen is one approach to accomplish this. Although numerous light-absorbing materials have been explored for green hydrogen production, the majority of them disintegrate fast when submerged in water.

The most efficient light-harvesting materials, for example, are perovskites, which are unstable in water and contain lead. Because of the risk of leakage, scientists have been working to develop lead-free alternatives.

Bismuth oxyiodide (BiOI) is one such alternative. So far, it was overlooked as a non-toxic semiconductor option for solar fuel applications due to its low water stability. But based on previous studies into the material's potential, the researchers chose to pick BiOI for creating green hydrogen.

The study's findings were published in Nature Materials.

The researchers created devices that mimicked the natural photosynthesis process in plant leaves. These artificial leaf devices, made of BiOI and other eco-friendly materials, absorb sunlight and produce O2, H2, and CO.

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 was applied to the strong oxide-based device structure. As a result, BiOI's light-absorbing pixels' stability was increased from minutes to a few months.

This is a major discovery that elevates BiOI to the status of a feasible light harvester capable of producing stable green hydrogen.

Dr Virgil Andrei, a Research Fellow at St John's College, University of Cambridge, and scientists from Imperial College London, who co-led the research, said that even if certain pixels were incorrect, they were able to separate them so that they didn't influence the remainder. This meant the researchers could maintain the little pixel's performance over a greater area.

These findings show that these novel devices have the potential to outperform conventional light absorbers. The new methods for improving the stability of BiOI artificial leaf devices can now be applied to other unique systems, assisting in their commercialisation.