🎤講師： Prof. Jeongsuk Seo（Associate Professor、Chonnam National University）
Prof. Jeongsuk Seo is an Associate Professor at Chonnam National University (Republic of Korea). She received her Ph.D. in Chemical Engineering from the University of Tokyo in 2014 under the supervision of Professor Kazunari Domen. After her Ph.D., she conducted postdoctoral research at the University of Tokyo on photocatalytic and photoelectrochemical water splitting. Prior to academia, she worked as a lithium-ion battery cell engineer at Samsung SDI. Her current research focuses on semiconductor and electrocatalyst materials for sustainable hydrogen production, particularly solar-driven seawater splitting and photoelectrocatalysis.

📢題目：Sunlight-driven Seawater Splitting of Perovskite Oxynitrides for Renewable Hydrogen Production

📆日時：2月12日（木）午後14：00～16：00

📍場所：広島大学工学部A3棟 1F 131会議室

🔷要旨：Photoelectrochemical (PEC) hydrogen production from seawater is an attractive strategy for solar fuel generation because seawater constitutes about 97% of Earth’s water. Perovskite-type oxynitride semiconductors, AB(O,N)₃ (A = Ca, Sr, Ba, La; B = Ti, Nb, Ta), absorb visible light up to 750 nm and possess suitable band positions for driving water and other redox reactions, enabling high theoretical solar-to-hydrogen efficiencies. However, their PEC activity in neutral electrolytes has been limited by sluggish oxygen evolution reaction (OER) kinetics. In chloride-containing seawater, the chlorine evolution reaction (CER), a two-electron oxidation process, can provide a kinetically faster alternative to OER, despite being thermodynamically less favorable. We demonstrate this concept using a highly crystalline, porous SrNbO₂N photoanode grown on a Nb substrate via oxidation and flux-assisted nitridation. In 0.2 M NaPi buffer (pH 6.4), the SrNbO₂N/Nb electrode showed measurable OER activity, while the addition of 0.5 M NaCl increased the photocurrent by a factor of three and lowered the onset potential by 0.1 V_RHE, indicating preferential CER. A more stable and photoactive BaTaO₂N/Ta photoanode was further evaluated in artificial seawater across different pH values. Product analysis (H₂, O₂, and HOCl/ClO⁻) and the use of electrocatalysts revealed conditions that enhance both seawater splitting efficiency and CER selectivity. These results highlight oxynitride photoelectrodes as promising platforms for efficient PEC hydrogen production from neutral seawater.