Photoelectrochemical Properties and Photostabilities of High Surface Area CuBi2O4 and Ag-Doped CuBi2O4 Photocathodes

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• 作者：Donghyeon Kang ; James C. Hill ; Yiseul Park ; Kyoung-Shin Choi
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：June 28, 2016
• 年：2016
• 卷：28
• 期：12
• 页码：4331-4340
• 全文大小：540K
• 年卷期：0
• ISSN：1520-5002

文摘

Electrochemical synthesis methods were developed to produce CuBi<sub>2sub>O<sub>4sub>, a promising p-type oxide for use in solar water splitting, as high surface area electrodes with uniform coverage. These methods involved electrodepositing nanoporous Cu/Bi films with a Cu:Bi ratio of 1:2 from dimethyl sulfoxide or ethylene glycol solutions, and thermally oxidizing them to CuBi<sub>2sub>O<sub>4sub> at 450 °C in air. Ag-doped CuBi<sub>2sub>O<sub>4sub> electrodes were also prepared by adding a trace amount of Ag<sup>+sup> in the plating medium and codepositing Ag with the Cu/Bi films. In the Ag-doped CuBi<sub>2sub>O<sub>4sub>, Ag<sup>+sup> ions substitutionally replaced Bi<sup>3+sup> ions and increased the hole concentration in CuBi<sub>2sub>O<sub>4sub>. As a result, photocurrent enhancements for both O<sub>2sub> reduction and water reduction were achieved. Furthermore, while undoped CuBi<sub>2sub>O<sub>4sub> electrodes suffered from anodic photocorrosion during O<sub>2sub> reduction due to poor hole transport, Ag-doped CuBiO<sub>4sub> effectively suppressed anodic photocorrosion. The flat-band potentials of CuBi<sub>2sub>O<sub>4sub> and Ag-doped CuBi<sub>2sub>O<sub>4sub> electrodes prepared in this study were found to be more positive than 1.3 V vs RHE in a 0.1 M NaOH solution (pH 12.8), which make these photocathodes highly attractive for use in solar hydrogen production. The optimized CuBi<sub>2sub>O<sub>4sub>/Ag-doped CuBi<sub>2sub>O<sub>4sub> photocathode showed a photocurrent onset for water reduction at 1.1 V vs RHE, achieving a photovoltage higher than 1 V for water reduction. The thermodynamic feasibility of photoexcited electrons in the conduction band of CuBi<sub>2sub>O<sub>4sub> to reduce water was also confirmed by detection of H<sub>2sub> during photocurrent generation. This study provides new understanding for constructing improved CuBi<sub>2sub>O<sub>4sub> photocathodes by systematically investigating photocorrosion as well as photoelectrochemical properties of high-quality CuBi<sub>2sub>O<sub>4sub> and Ag-doped CuBi<sub>2sub>O<sub>4sub> photoelectrodes for photoreduction of both O<sub>2sub> and water.