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      Enhanced performance of doped BiOCl nanoplates for photocatalysis: understanding from doping insight into improved spatial carrier separation

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          Abstract

          Doped BiOCl nanoplates enclosed with (001) and (110) facets were fabricated to demonstrate the role of doping in promoting spatial carrier separation.

          Abstract

          The spatial carrier separation of semiconductor photocatalysts with different crystal facets has been utilized for improving photocatalytic efficiency. However, the efficiency of spatial carrier separation is restricted in these facet-based semiconductor photocatalysts. Herein, we aim to steer spatial separation of photoexcited carriers by implementing a doping strategy and select BiOCl nanoplates as a model photocatalyst to investigate spatial carrier separation and photocatalytic performance. High-resolution transmission electron microscopy shows that doped BiOCl single crystalline nanoplates have (001) crystal facets on their top and bottom surfaces, while they have (110) crystal facets at their four side surfaces. The photoelectrochemical results show that doping enhances the separation efficiency of the photoexcited carriers. Meanwhile, the phenomenon that the valence band decreases gradually while photocatalytic degradation efficiency increases with increasing dopant concentration implies that the increase of photocatalytic efficiency originates from the effective separation of the photoexcited carriers. Furthermore, photodeposition results of BiOCl and doped BiOCl nanoplates indicate an enhanced spatial separation of photoexcited electrons and holes between (001) and (110) crystal facets. The doped BiOCl nanoplates exhibit significant efficiency for pollutant degradation under visible light. The results obtained demonstrate the rational design of spatial carrier separation with different crystal orientations for more efficient solar-driven photocatalytic conversion.

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          Most cited references43

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          Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4.

          Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.
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            All-solid-state Z-scheme in CdS-Au-TiO2 three-component nanojunction system.

            Natural photosynthesis, which achieves efficient solar energy conversion through the combined actions of many types of molecules ingeniously arranged in a nanospace, highlights the importance of a technique for site-selective coupling of different materials to realize artificial high-efficiency devices. In view of increasingly serious energy and environmental problems, semiconductor-based artificial photosynthetic systems consisting of isolated photochemical system 1 (PS1), PS2 and the electron-transfer system have recently been developed. However, the direct coupling of the components is crucial for retarding back reactions to increase the reaction efficiency. Here, we report a simple technique for forming an anisotropic CdS-Au-TiO2 nanojunction, in which PS1(CdS), PS2(TiO2) and the electron-transfer system (Au) are spatially fixed. This three-component system exhibits a high photocatalytic activity, far exceeding those of the single- and two-component systems, as a result of vectorial electron transfer driven by the two-step excitation of TiO2 and CdS.
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              Steering charge kinetics in photocatalysis: intersection of materials syntheses, characterization techniques and theoretical simulations.

              Charge kinetics is highly critical in determining the quantum efficiency of solar-to-chemical conversion in photocatalysis, and this includes, but is not limited to, the separation of photoexcited electron-hole pairs, utilization of plasmonic hot carriers and delivery of photo-induced charges to reaction sites, as well as activation of reactants by energized charges. In this review, we highlight the recent progress on probing and steering charge kinetics toward designing highly efficient photocatalysts and elucidate the fundamentals behind the combinative use of controlled synthesis, characterization techniques (with a focus on spectroscopic characterizations) and theoretical simulations in photocatalysis studies. We first introduce the principles of various processes associated with charge kinetics that account for or may affect photocatalysis, from which a set of parameters that are critical to photocatalyst design can be summarized. We then outline the design rules for photocatalyst structures and their corresponding synthetic approaches. The implementation of characterization techniques and theoretical simulations in different steps of photocatalysis, together with the associated fundamentals and working mechanisms, are also presented. Finally, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields.
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                Author and article information

                Journal
                JMCAET
                Journal of Materials Chemistry A
                J. Mater. Chem. A
                Royal Society of Chemistry (RSC)
                2050-7488
                2050-7496
                2017
                2017
                : 5
                : 24
                : 12542-12549
                Affiliations
                [1 ]State Key Laboratory for Powder Metallurgy
                [2 ]Central South University
                [3 ]Changsha 410083
                [4 ]People's Republic of China
                [5 ]School of Materials Science and Engineering
                [6 ]University of New South Wales
                [7 ]Sydney 2052
                [8 ]Australia
                Article
                10.1039/C7TA02724A
                b5091e48-68dd-4ef6-99a3-e28fc1b8df68
                © 2017
                History

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