On Feb. 6, a joint research team at the Ulsan National Institute of Science and Technology (UNIST), led by Professor Lee Jae-sung, Professor Jang Ji-wook, and Professor Seok Sang-il from the Department of Energy and Chemical Engineering and Professor Lim Han-kwon from the Graduate School of Carbon Neutrality, announced that it has developed a green hydrogen production technology utilizing solar energy, which boasts high efficiency, durability, and scalability.
The research team addressed the drawbacks of perovskite solar cells and significantly increased the size of the photoelectrodes by 10,000 times, enhancing the practicality of the technology. Solar hydrogen technology is an ideal green hydrogen production method that utilizes solar energy, the most abundant renewable energy source on Earth, to electrolyze water and obtain hydrogen.
Professor Lee Jae-sung explained, “Recent advancements have somewhat addressed efficiency issues but the developed technology has been confined to small-scale laboratory devices. To move towards practical application, scaling up is necessary.”
The UNIST research team adopted perovskite as the material for the photoelectrode, which is efficient and relatively inexpensive. Perovskite solar cells are a research and development field led by professors at UNIST, including Professor Seok Sang-il, who participated in this study.
However, perovskite solar cells have low stability against ultraviolet rays in sunlight and moisture in the air. Especially, for producing hydrogen by electrolyzing water, the photoelectrode needs to be submerged in water. The research team has addressed both of these issues.
The research team manufactured the most UV-stable perovskite by using formamidinium instead of the conventional methylammonium as the cation in perovskite. It also ensured stability in water by completely sealing the contact surface with water using nickel foil.
Typically, photoelectrodes for research and development are small, less than 1 square centimeter in size, while practical-scale ones need to be scaled up to 1 square meter, requiring about a 10,000-fold increase. During the scale-up process, hydrogen production efficiency tends to decrease, necessitating techniques to minimize this reduction.
To scale up the photoelectrode, the research team employed a module-based design wherein small photoelectrodes are interconnected and arranged in a consistent size. Similar to stacking blocks, small photoelectrodes are repeated horizontally and vertically to manufacture large-area photoelectrodes.
With this scaled-up module, the research team achieved a solar-to-hydrogen conversion efficiency of over 10 percent, meeting the minimum requirement for commercialization. This efficiency level represents the world’s highest efficiency for large-area photoelectrodes.
Dr. Dharmesh Hansora, the lead author of the study, stated, “The photoelectrode developed in this study maintained high efficiency even on a large scale.” She further remarked, “If we focus on on-site validation for the commercialization of green hydrogen production in the future, we can expect solar-based green hydrogen technology to be commercialized before 2030.”
The findings of this study were published online in Nature Energy, one of the top academic journals in the field of energy, on Jan. 23. The research was conducted with support from the Ministry of Science and ICT’s Climate Change Response Project and the BrainLink Project.
The title of the paper is “All-perovskite-based Unassisted Photoelectrochemical Water Splitting System for Efficient, Stable, and Scalable Solar Hydrogen Production.”