Manipulation of charge carrier flow in a Bi 4 NbO 8 Cl nanoplate with metal loading for water splitting photocatalysis Kanta Ogawa 1 , Ryota Sakamoto 2 , Chengchao Zhong 2 , Hajime Suzuki 2 , Kosaku Kato 3 , Osamu Tomita 2 , Kouichi Nakashima 4 , Akira Yamakata 3 , Takashi Tachikawa 5 , Akinori Saeki 6 , Hiroshi Kageyama 2 , Ryu Abe 2 1 Imperial College London, UK, 2 Graduate School of Engineering, Kyoto University, Japan, 3 Toyota Technological Institute, Japan, 4 College of Engineering, Japan 5. Kobe University, Japan, 6 Osaka University, Japan Semiconductor photocatalysis will serve as one of the important platforms for futuristic hydrogen production, where the separation of photoexcited charge carriers in semiconductors is essential for efficient solar energy conversion. However, underlying mechanisms therein and their control strategies are still not fully established. In this study, we successfully manupulate carrier flows in Sillén-Aurivillius layered oxychloride Bi 4 NbO 8 Cl for efficient charge separation. Despite the band positions of Bi 4 NbO 8 Cl suitable for H 2 production 1 , the H 2 evolution activity of Bi 4 NbO 8 Cl was negligible. We reveal that, in the absence of a cocatalyst, both photoexcited electrons and holes travel along the in-plane direction based on the band dispersions, resulting in recombination at the edge of the nanoplate (Fig. A). On the other hand, site-selective deposition of a Rh cocatalyst on the edge of the Bi 4 NbO 8 Cl plate crystal realizes the in-plane and out-of-plane flows of photoexcited electrons and holes (“orthogonal” carrier flows), respectively, thus enabling spatial charge separation (Fig. B). As a result, a significant improvement in the H 2 generation is achieved with Rh-modified Bi 4 NbO 8 Cl. 2
References 1. H. Fujito, H. Kunioku, D. Kato, H. Suzuki, M. Higashi, H. Kageyama and R. Abe, J. Am. Chem. Soc. , 2016, 138 , 2082–2085. 2. K. Ogawa, R. Sakamoto, C. Zhong, H. Suzuki, K. Kato, O. Tomita, K. Nakashima, A. Yamakata, T. Tachikawa, A. Saeki, H. Kageyama and R. Abe, Chem. Sci., 2022, 13 , 3118–3128
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