Role and Function of Noble-Metal/Cr-Layer Core/Shell Structure Cocatalysts for Photocatalytic Overall Water Splitting Studied by Model Electrodes

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• 作者：Masaaki Yoshida ; Kazuhiro Takanabe ; Kazuhiko Maeda ; Akio Ishikawa ; Jun Kubota ; Yoshihisa Sakata ; Yasunari Ikezawa ; Kazunari Domen
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：June 11, 2009
• 年：2009
• 卷：113
• 期：23
• 页码：10151-10157
• 全文大小：198K
• 年卷期：v.113,no.23(June 11, 2009)
• ISSN：1932-7455

文摘

The mechanism of hydrogen evolution by a core/shell noble-metal/Cr₂O₃ particulate as a highly efficient cocatalyst for overall water splitting under visible light using the photocatalyst (Ga_1−xZn_x)(N_1−xO_x) is investigated by electrochemical and in situ spectroscopic measurements of model electrodes. The electrodes are prepared by electrochemical deposition of 1.8−3.5 nm thick Cr₂O₃ films on Rh and Pt plates and are evaluated as model systems of Rh/Cr₂O₃ and Pt/Cr₂O₃ core/shell particulates, which have previously been applied effectively as cocatalysts for hydrogen evolution in this system. Proton adsorption/desorption and H₂ evolution currents are observed for both the Cr₂O₃-coated and the bare electrodes, and the infrared absorption band due to Pt−H stretching (2039 cm⁻¹) is apparent for both the coated and the bare electrodes. These observations indicate that the Cr₂O₃ layer does not interfere with proton reduction or hydrogen evolution and that proton reduction takes place at the Cr₂O₃/Pt interface. However, the reduction of oxygen to water is suppressed only in the Cr₂O₃-coated samples. The Cr₂O₃ layer is thus permeable to protons and the evolved hydrogen molecules, but not to oxygen. Cocatalyst modification by thin films with this type of functionality thus appears to be a useful strategy for improving the efficiency of photocatalytic overall water splitting.