Hydrogen generated by solar pixels

Researchers from the University of Cambridge and Imperial College London have utilized a photoactive material as a non-toxic alternative to semiconductors for the production of green hydrogen.

Due to the importance of hydrogen fuel in the transition to full decarbonisation and the goal of attaining net zero emissions by 2050, it was demonstrated that easily available oxide and carbon-based materials may be used to produce long-lasting, clean hydrogen from water.

Considering that the majority of hydrogen is derived from fossil fuels, it is essential to find alternatives, such as devices that capture sunlight and split water. Current earth-abundant light-absorbing materials, such as perovskites, are limited in terms of performance or stability, therefore the team sought to enhance the generation of solar fuel in a sustainable manner.

Oxide-based materials are excellent choices for energy applications due to their resistance to air and water. Bismuth oxyiodide (BiOI), which had not been previously attempted for solar fuel applications, was utilized here as an efficient light harvester. BiOI possesses the correct energy levels for water splitting, as well as fabrication simplicity, minimal toxicity, and beneficial stability.

The researchers developed artificial leaf devices that mimic the natural photosynthesis process in plant leaves, but produce fuels like hydrogen instead of carbohydrates. The devices were constructed from BiOI and other eco-friendly substances, and they harvested sunlight to make O2, H2 and CO. The light absorber’s effectiveness and stability were greatly enhanced by sandwiching it between layers of robust oxide and carbon, and then coating the structure with a water-repellent graphite paste to prevent moisture infiltration.

The oxide layers boost the ability to create hydrogen when compared to BiOI alone, whereas artificial leaf devices comprised of several light-harvesting areas, or pixels, performed better than conventional devices with a single bigger pixel of the same total size. The method increased the BiOI light-absorbing pixels’ stability from minutes to many months.

Any defective pixels can be isolated without affecting the rest, allowing them to maintain the performance of the small pixels over a greater region. This enhanced performance permits these devices to not only produce hydrogen, but also convert CO2 into synthesis gas, a crucial intermediary in the commercial production of chemicals and pharmaceuticals.