New Precursor Route Using a Compositionally Flexible Layered Oxide and Nanosheets for Improved Nitrogen Doping and Photocatalytic Activity

• Published in: ACS applied energy materials Vol. 1; no. 4; pp. 1734 - 1741
• Main Authors: Maeda, Kazuhiko, Tokunaga, Yuki, Hibino, Keisuke, Fujii, Kotaro, Nakaki, Hiroyuki, Uchiyama, Tomoki, Eguchi, Miharu, Lu, Daling, Ida, Shintaro, Uchimoto, Yoshiharu, Yashima, Masatomo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.04.2018
• Subjects: artificial photosynthesis; mixed anion compounds; water splitting; layered materials; heterogeneous photocatalysis; nanosheets
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.8b00256

Nitrogen doping into a metal oxide is a conventional method to prepare a visible-light-responsive photocatalyst. However, the charge imbalance that results from aliovalent anion substitution (i.e., O2–/N3– exchange) generally limits the concentration of nitrogen that can be introduced into a metal oxide, which leads to insufficient visible-light absorption capability. Here we report an effective route to synthesize nitrogen-doped metal oxide using KTiNbO5, which is a compositionally flexible layered oxide and can be exfoliated into nanoscale sheets. KTiNbO5 has a unique layered structure, in which Ti4+ and Nb5+ coexist in the same two-dimensional sheet, and controllable Ti4+/Nb5+ ratios while maintaining the original KTiNbO5-type structure. The use of a Nb-rich oxide precursor could allow for the improvement in the introduction of nitrogen compared with stoichiometric KTiNbO5 during thermal ammonolysis with ammonia gas. Reassembled KTiNbO5 nanosheets with a larger surface area were found to be more useful as a precursor than the layered precursor in terms of nitrogen introduction and thus yielded more pronounced visible-light absorption and photocatalytic activity for water oxidation.