This piece spotlights a study exploring the photoelectrochemical water splitting mechanism on a Si photoanode fortified with a TiOx layer of varying defect densities. The study was conducted in the labs of Dr. Ansoon Kim from the Korea Research Institute of Standards & Science (KRISS). Credit: Korea Research Institute of Standards and Science (KRISS)
KRISS demonstrated the carrier transport mechanism of a photoanode protected by a film, aiming to bolster green hydrogen production. This development could support the creation of carbon-neutral green hydrogen and synthetic photosynthesis.
Hydrogen, increasingly recognized as a clean and potent energy source, raises questions about its environmental impact. Presently, the most common hydrogen variant is “grey hydrogen,” derived from fossil fuels. Given the greenhouse gas emissions associated with its production, grey hydrogen cannot truly be considered eco-friendly. The emergence of “green hydrogen,” free from carbon emissions, remains an impending development.
Under President Hyun-min Park’s guidance, the Korea Research Institute of Standards and Science (KRISS) has demonstrated a potential solution for a durable, efficient photoanode protected by a film, essential for hydrogen production via solar water splitting. This is anticipated to accelerate the advent of eco-friendly “green hydrogen.”
Green hydrogen is carbon-emission free, being produced with renewable energy. A typical method for green hydrogen production is photoelectrochemical water splitting using a photoanode. The photoanode, submerged in electrolytes and able to absorb sunlight, directly splits water into hydrogen and oxygen using the absorbed solar energy. However, the photoanode’s direct contact with the electrolyte makes it vulnerable to surface corrosion, leading to the application of protective coatings on its surface.
Oxide materials like titanium dioxide (TiO2) often serve as protective films for photoanodes. While these materials are poor conductors of electricity, they can be manipulated to improve conductivity by introducing oxygen defects to facilitate charge transport. Extending the longevity of photoanodes hinges on developing a robust protective film that can prevent electrode corrosion while maintaining optimal electrical conductivity.
Credit: Korea Research Institute of Standards and Science (KRISS)
KRISS has pioneered a technique to systematically adjust the oxygen defect levels in a titanium dioxide (TiO2) protective film on a photoanode, to optimize hydrogen production efficiency. The research team identified the ideal defect levels to maximize photoanode longevity and hydrogen production, through X-ray photoelectron spectroscopy and electrochemical analysis, thereby deciphering the role of oxygen defects in charge transfer mechanisms.
This research innovatively proposes a direct production method that controls oxygen defect levels, in contrast to previous studies that relied on randomly formed oxygen defects during manufacturing. Experimentally, photoanodes lacking protective films exhibited rapid degradation within an hour, causing hydrogen production efficiency to plunge below 20% of the original state. However, photoanodes with optimized protective films sustained a hydrogen production efficiency of over 85%, even after 100 hours.
This breakthrough could enhance photoanode efficiency and longevity and could be leveraged in other clean technologies employing photoanodes. An example includes artificial photosynthesis technology that harnesses solar energy to capture carbon dioxide and convert it into a chemical energy source.
Dr. Ansoon Kim, a lead researcher at KRISS Interdisciplinary Materials Measurement Institute, noted, “This approach can extend the photoanode lifespan nearly tenfold, significantly promoting the commercialization of green hydrogen.”
KRISS aims to conduct additional research to ascertain the optimal oxygen defect levels and fundamental principles to maximize the lifespan of photoanodes.
The reference for this study is: “Role of defect density in the TiOx protective layer of the n-Si photoanode for efficient photoelectrochemical water splitting” by Songwoung Hong, Woo Lee, Yun Jeong Hwang, Seungwoo Song, Seungwook Choi, Hyun Rhu, Jeong Hyun Shimbe, and Ansoon Kim, 13 January 2023, Journal of Materials Chemistry A.
DOI: 10.1039/D2TA07082K
The study received funding from the National Research Foundation of Korea.
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Frequently Asked Questions (FAQs) about Green Hydrogen Production
What is the main focus of the research conducted by KRISS?
The research conducted by the Korea Research Institute of Standards & Science (KRISS) mainly focuses on improving the process of photoelectrochemical water splitting. They have developed a mechanism that enhances the production of green hydrogen by optimizing the protective film on a photoanode, a crucial component for hydrogen production via solar water splitting.
What is green hydrogen, and how does it differ from grey hydrogen?
Green hydrogen is a form of hydrogen that is produced using renewable energy sources, and it does not produce any carbon emissions during its production. On the other hand, grey hydrogen, currently the most common form of hydrogen, is derived from fossil fuels. The process of producing grey hydrogen leads to greenhouse gas emissions, making it not as environmentally friendly as green hydrogen.
What is the importance of the protective film on a photoanode?
The protective film on a photoanode plays a critical role in preventing surface corrosion. Because the photoanode is in direct contact with an electrolyte during the process of photoelectrochemical water splitting, it’s prone to surface corrosion. The protective film, often made of oxide materials such as titanium dioxide (TiO2), helps to maintain the lifespan and efficiency of the photoanode.
What is the potential impact of the research findings on the future of clean energy?
The findings from the research could significantly impact the future of clean energy by enhancing the efficiency and lifespan of photoanodes, which are essential in the production of green hydrogen. The approach developed by KRISS could also be applied to other clean technologies that rely on photoanodes, such as artificial photosynthesis technology that captures carbon dioxide and converts it into a chemical energy source using solar energy.
Who funded the research conducted by KRISS?
The research conducted by KRISS was funded by the National Research Foundation of Korea.
More about Green Hydrogen Production
- Korea Research Institute of Standards and Science
- National Research Foundation of Korea
- Journal of Materials Chemistry A
- Green Hydrogen: A Guide to Understanding its Production and Uses
- Artificial Photosynthesis
- Photoelectrochemical Water Splitting
