According to the current study, devices comprised of commonly accessible oxide and carbon-based materials can manufacture pure hydrogen from water for weeks.
The findings, led by Dr. Virgil Andrei, a Research Fellow at St John’s College, University of Cambridge, in collaboration with Imperial College London academics, could help solve one of the key issues in solar fuel production: current earth-abundant light-absorbing materials are limited by either their performance or stability.
Materials for light-harvesting that have yet to be discovered
The move to full decarbonization and the UK’s target of net-zero emissions by 2050 will rely heavily on hydrogen fuel. Because the majority of hydrogen is presently 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 generate green hydrogen is one approach to do this.
Although numerous light-absorbing materials have been explored for green hydrogen generation, the majority of them disintegrate fast when submerged in water. Perovskites, for example, are the most efficient light-harvesting materials, although they are unstable in water and contain lead. As a result of the potential of leaking, scientists have been attempting to produce lead-free alternatives.
Because of its low water stability, bismuth oxyiodide (BiOI) has been disregarded as a non-toxic semiconductor option for solar fuel applications. Researchers opted to review the promise of BiOI for the generation of green hydrogen based on earlier studies into the material’s potential.
Dr. Robert Hoye, a lecturer in Imperial College London’s Department of Materials, explained: “Bismuth oxyiodide is an intriguing photoactive material with the correct energy levels for water splitting. We proved a few years ago that solar cells made of BiOI are more stable than those made of state-of-the-art perovskite light absorbers. We wanted to investigate if we could apply that stability to the creation of green hydrogen.”
Professor Judith Driscoll of the University of Cambridge’s Department of Materials Science and Metallurgy said: “We’ve been working on this material for a while because of its broad range of possible uses, as well as its ease of production, low toxicity, and high stability. It was fantastic to bring together the experience of several research groups from around Cambridge and Imperial.”
Solar fuel manufacturing makes a breakthrough
The researchers developed gadgets that mirrored the natural photosynthesis process in plant leaves, but instead of carbohydrates, they produce fuels like hydrogen. These artificial leaf gadgets, composed of BiOI and other environmentally friendly materials, capture sunlight and create O2, H2, and CO.
By sandwiching BiOI between two oxide layers, researchers were able to improve the stability of these artificial leaf devices. The water-repellent graphite paste was applied to the strong oxide-based device construction to avoid moisture penetration. The stability of the bismuth oxyiodide light-absorbing pixels was extended from minutes to a few months as a result of this, including the period the devices were stored.
This is a major discovery that elevates BiOI to the status of a feasible light harvester capable of producing stable green hydrogen.
One of the co-led authors, Dr. Robert Jagt (Department of Materials Science and Metallurgy, University of Cambridge), remarked, “These oxide layers boost the capacity to create hydrogen compared to stand-alone BiOI.”
Researchers also discovered that artificial leaf devices with several light-collecting sections (called ‘pixels’) performed better than devices with a single bigger pixel of the same overall size. This discovery might make scaling up revolutionary light harvesters for sustainable fuel generation easier and faster.
Dr. Virgil Andrei, a co-lead author from the University of Cambridge’s Department of Chemistry, explains: “Even if certain pixels are defective, we were able to isolate them so that they do not impact the remainder of the image. As a result, we were able to maintain the little pixel’s performance over a greater region.” This improved performance allowed the device to create hydrogen as well as decrease CO2 to synthesize gas, a key intermediary in the industrial synthesis of chemicals and medicines.
Considering the future
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 may now be applied to other unique systems, assisting in their commercialization.
“This is a wonderful development! At the time, only a few solar fuel systems demonstrate stability that is suitable for real-world applications. We take a step closer to developing a circular fuel economy with this study “One of the corresponding authors, Prof Erwin Reisner (Department of Chemistry, Cambridge), stated.
The findings were reported in the Nature Materials journal.
