Professor Sanghan Lee's research team is the first to create high-quality monocrystalline photoanodes for efficient hydrogen production 

□ A new method of forming a monocrystalline photoanode capable of producing more hydrogen for environmentally friendly energy has been proposed at the Gwangju Institute of Science and Technology (GIST, President Seung Hyeon Moon) by Professor Sanghan Lee Sang-Hwan of the School of Materials Science and Engineering. For the first time, Professor Lee's research team has shown that a very thin, high-quality monocrystalline photoanode can be easily formed by adding a functional layer having a thickness of only several nanometers.

 

□ A photoanode is an electrode made of a material that absorbs sunlight to generate electrons with its relatively narrow bandgap. When water reacts with the electrons generated by a photoanode, hydrogen is released that can then be used as an environmentally friendly renewable energy source. Bismuth vanadate (BiVO4) has been a common photoanode material, but manufacturing a high-quality monocrystalline photoanode from it has been difficult until now because the fundamental aspects of bismuth vanadate's optical behavior has been lacking.

□ The researchers first experimentally demonstrated that a high-quality monocrystalline bismuth vanadate photoanode a few nanometers thick can be grwon. As a result, when the tungsten oxide (WO 3) was used as the interlayer, the bismuth vanadate photoanode was grown as a high-quality monocrystalline due to the decrease of the lattice mismatch. In addition, the tungsten oxide insert first acts as a charge transport layer due to a lower energy level compared to bismuth vanadate and the second surface the optical current density is improved by 10 times area due to surface energy differences. The fact that the photocurrent density is high means that the efficiency of converting light energy received from the sunlight into electric energy is high. The generated electric energy can split water to produce hydrogen. In other words, simply by adding a layer of tungsten oxide only a few nanometers thick, high quality monocrystalline bismuth vanadate photoanodes can be formed, resulting in high efficiency hydrogen production.

□ Professor Sanghan Lee said, "This study has shown that high quality monocrystalline bismuth vanadate photoanode can be formed using a interlevel layer a few nanometers thick. The results of this study are expected to provide a fundamental understanding of the photoactivity behavior of bismuth vanadate and will lead to a breakthrough in the field of eco-friendly energy production technology in the future."

□ This research was supported by the “Climate Technology Development and Application” research project through a grant provided by GIST in 2017, and their paper entitled "Template-engineered epitaxial BiVO4 photoanodes for efficient solar water splitting" was authored by Jaesun Song, Jaeseong Cha, Mi Gyoung Lee, Hye Won Jeong, Sehun Seo, Ji Ae Yoo, Taemin Ludvic Kim, Jongmin Lee, Heesung No, Do Hyun Kim, Sang Yun Jeong, Hyunji An, Byoung Hun Lee, Chung Wung Bark, Hyunwoong Park, Ho Won Jang, and Sanghan Lee and was published on August 14, 2017, in Journal of Materials Chemistry A.