Enhancing Charge Separation in Metallic Photocatalysts: A Case Study of the Conducting Molybdenum Dioxide |
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Authors: | Zhuofeng Hu Gang Liu Xingqiu Chen Zhurui Shen Jimmy C Yu |
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Affiliation: | 1. Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China;2. Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China;3. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China;4. Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin, China |
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Abstract: | A new visible‐light responsive metallic photocatalyst, nanostructured MoO2, has been discovered. The metallic nature of MoO2 is confirmed by valance X‐ray photoelectron spectroscopy spectrum and theoretical calculations. However, MoO2 itself shows only moderate activity due to the serious charge recombination, a general disadvantage of metallic photocatalysts. The findings suggest that its effective charge diffusion length Lp is smaller than 1.0 nm while the separation efficiency ηsep is less than 10%. Therefore, only the periphery of the metallic MoO2 can effectively contribute to photocatalysis. This limitation is overcome by integrating MoO2 in a hydrothermal carbonation carbon (HTCC) matrix (mainly contains semiconductive polyfuran). This simple chemical modification brings two advantages: (i) an internal electric field is formed at the interface between MoO2 and HTCC due to their appropriate band alignment; (ii) the nanostructured MoO2 and the HTCC matrix are intertwined with each other intimately. Their small size and large contact area promote charge transfer, especially under the internal electric field. Therefore, the separation rate of photoexcited charge carrier in MoO2 is greatly enhanced. The activity increases by 2.4, 16.8, and 4.0 times in photocatalytic oxygen evolution, dyes degradation, and photoelectrochemicl cell, respectively. The new approach is helpful for further development of metallic photocatalysts. |
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Keywords: | charge separation HTCC metallic photocatalysts MoO2 |
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