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Ag2-xO with highly exposed{111}crystal facets for efficient electrochemical oxygen evolution:Activity and mechanism

Chinese Journal of Catalysis 2020年第11期41卷 1706-1714页

作者： Xiao-Feng Zhang Jian-Sheng Li Wan-Sheng You Zai-Ming Zhu School of Chemistry and Chemical Engineering Liaoning Normal UniversityDalian 116029LiaoningChina

A series of Ag2–xO/FTO-i electrodes(where i denotes the current density during the electrodeposition, and i = 0.5, 1, 2, 3, 4, or 7) was fabricated in 0.1 M K2B4O7 electrolyte containing Ag+ ions by galvanostatic electrocrystallization. The electrode composition and morphology were characterized using X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results reveal that the electrode films consist of Ag2O, but some of the Ag+ ions on the {111} crystal facets are oxidized into Ag2+ ions. Furthermore, the Ag2–xO/FTO-1 electrode shows a triangular slice shape of a parallel matrix with a larger exposed area of {111} crystal facets than other Ag2–xO/FTO-i(i = 0.5, 2, 3, 4, or 7) electrodes. Electrocatalytic experiments prove that the Ag2–xO/FTO-1 electrode produces the highest oxidative current density, has an overpotential of 417 m V at 10 m A cm–2, and has a Tafel slope of 47 m V dec–1 in 0.1 M K2B4O7. Electrochemical impedance spectra indicate that Ag2–xO/FTO-1 electrodes have the best ability for charge transfer. In addition, in the I-t test over 10 h, the current density decreased 4%. Fortunately, both O–O and Ag2+ species were detected after electrocatalysis and a possible mechanism for the oxygen evolution reaction is proposed in which the formation of Ag2+ and O–O species on {111} facets plays a critical role.

关键词： Ag2O crystal facet Ag2+ions Electrocatalysis Water oxidation Oxygen evolution reaction

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Ultrahigh quantum efficiency photodetector and ultrafast reversible surface wettability transition of square In2O3 nanowires

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Nano Research 2017年第8期10卷 2772-2781页

作者： Ming Meng Xinglong Wu Xiaoli Ji Zhixing Gan Lizhe Liu Jiancang Shen Paul K. Chu School of Physics and Telecommunication Engineering Zhoukou Normal University Zhoukou 466001 China Key Laboratory of Modern Acoustics MOE Institute of Acoustics Collaborative Innovation Center of Advanced Microstructures Notional Laboratory of Solid State Microstructures Nanjing University Nonjing 210093 China School of Electronic Science and Engineering Nanjing University Nanjing 210093 China Key Laboratory of Optoelectronic Technology of Jiangsu Province School of Physical Science and Technology Nanjing Normal University Nanjing 210023 China Department of Physics and Materials Science City University ofHong Kong Tat Chee Avenue Kowloon Hong Kong China

Due to a large surface-to-volume ratio, the optoelectronic performance of low- dimensional semiconductor nanostructure-based photodetectors depends in principle on chemisorption/photodesorption at the exposed surface, but practical examples that show such an effect are still unavailable. Some theoretical calculations have predicted that the {001} facets of In2O3 can effectively accumulate photogenerated holes under irradiation, providing a model material to examine whether the facet cutting of nanowires （NWs） can boost their optoelectronic performance. Herein, we present the design and construction of a novel nanowire-based photodetector using square In2O3 NWs with four exposed {001} crystal facets. The photodetector delivers excellent optoelectronic performance with excellent repeatability, fast response speed, high spectral responsivity （Rλ）, and high external quantum efficiency （EQE）. The Rλ and EQE values are as high as 4.8 × 10^6 A/W and 1.46 × 10^9%, respectively, which are larger than those of other popular semiconductor photodetectors. In addition, the square In2O3 NWs show hydrophobic wettability as manifested by a contact angle of 118° and a fast photoinduced reversible switching behavior is observed.

关键词： square In2O3 nanowires crystal facet photodetector reversible wettability transition

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Meaningful comparison of photocatalytic properties of {001} and {101} faceted anatase TiO2 nanocrystals

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Science Bulletin 2016年第13期61卷 1003-1012页

作者： Yang Lu Yipeng Zang Haimin Zhang Yunxia Zhang Guozhong Wang Huijun Zhao Key Laboratory of Materials Physics Centre for Environmentaland Energy Nanomaterials Anhui Key Laboratory of Nanomaterials and Nanotechnology Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China University of Science and Technology of China Hefei 230026China Centre for Clean Environment and Energy Griffith UniversityGold Coast Campus Gold Coast QLD 4222 Australia

The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distinction in the photocatalytic oxidation activities between the {001}and {101} facets of anatase TiO_2 nanocrystals is still unclear and under debate. In this work, a simple photoelectrochemical method was employed to meaningfully quantify the intrinsic photocatalytic activities of {001} and{101} faceted TiO_2 nanocrystal photoanodes. The effective surface areas of photoanodes with different facets were measured based on the monolayer adsorption of phthalic acid on TiO_2 photoanode surface by an ex situ photoelectrochemical method, which were used to normalize the photocurrents obtained from different faceted photoanodes for meaningful comparison of their photocatalytic activities. The results demonstrated that the {001} facets of anatase TiO_2 nanocrystals exhibited much better photocatalytic activity than that of {101} facets of anatase TiO_2 nanocrystals toward photocatalytic oxidation of water and organic compounds with different functional groups(e.g.,–OH, –CHO, –COOH). Furthermore, the instantaneous kinetic constants of photocatalytic oxidation of pre-adsorbates on {001} faceted anatase TiO_2 photoanode are obviously greater than those obtained at {101} faceted anatase TiO_2 photoanode, further verifying the higher photocatalytic activity of {001} facets of anatase TiO_*** work provided a facile photoelectrochemical method to quantitatively determine the photocatalytic oxidation activity of specific exposed crystal facets of a photocatalyst, which would be helpful to uncover and meaningfully compare the intrinsic photocatalytic activities of different exposed crystal facets of a photocatalyst.

关键词： Anatase TiO2 crystal facet Photocatalysis Structure-activity relationships

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Photo-depositing Ru and RuO2 on Anatase TiO2 Nanosheets as Co-catalysts for Photocatalytic O2 Evolution from Water Oxidation

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Chinese Journal of Chemical Physics 2016年第5期29卷 585-590,I0002页

作者：米诗阳刘园旭汪文栋中国科学技术大学化学物理系中国科学院能量转换材料重点实验童合肥230026

TiO2 nanosheets mainly exposed （001） facet were prepared through a hydrothermal process with HF as the morphology-directing agent. Ru and RuO2 species were loaded by photo-deposition methods to prepare the photocatalysts. The structural features of the catalysts were characterized by X-ray di raction, transmission electron microscopy, inductively cou-pled plasma atomic emission spectrum, and H2 Temperature-programmed reduction. The photocatalytic property was studied by the O2 evolution from water oxidation, which was examined with respect to the in uences of Ru contents as well as the oxidation and reduction treatments, suggesting the charge separation effect of the Ru species co-catalysts on di erent facets of TiO2 nanosheets. In contrast to Ru/TiO2 and RuO2/TiO2 with the single deposited co-catalyst, the optimized catalyst 0.5%Ru-1.0%RuO2/TiO2 with dual co-catalysts achieved a much improved catalytic performance, in terms of the synergetic effect of dual co-catalysts and the enhanced charge separation effect.

关键词： Anatase TiO2 nanosheets Photocatalytic O2 evolution crystal facet Ru co-catalyst Charge separation

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Enhanced Visible-light-driven Photocatalytic Performance of In2O3-10aded TiO2 Nanocubes with Exposed （001） facet

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Chemical Research in Chinese Universities 2017年第6期33卷 934-938页

作者： GAO Bifen WAN Jianfeng HU Desheng CHEN Yilin LIN Bizhou Department of Applied Chemistry College of Materials Science and Engineering Huaqiao University Xiamen 361021 R R. China

The heterostructures of In2O3 nanoparticle loaded on anatase TiO2 nanocube with exposed （001） facet （In2O3/TiO2-nanocube） were fabricated via a two-step hydrothermal process. The crystal phase, morphology, mi- cro-stnmture and photo-absorption property of the products were characterized by FESEM, TEM, XRD, and UV-Vis diffuse reflectance spectroscopy. The results showed that the percentage of exposed （001） facet of TiO2 nanocube was about 33%. In2O3 nanoparticles were successfully decorated on the surface of TiO2 nanocube to form the In2O3/TiO2 heterojtmction. Photocurrent measurements confirmed that （001） faceted surface was advantageous for the charge carrier migration and separation in the composites. In comparison with bare TiO2 nanocube and In2O3/TiO2-nanoparticle, the In2O3/TiO2-nanocube heterostructures exhibited enhanced activity toward the degradation of rhodamine B and tetracycline under visible light irradiation, which was attributed to the synergic effect of In2O3/TiO2 heterojunction and the exposure of （001） facet.

关键词： Photocatalytic activity Heterojunction crystal facet In2O3-10aded TiO2 nanocube

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基于g-C3N4的Z-型光催化剂体系的构建及其光催化性能的研究

基于g-C3N4的Z-型光催化剂体系的构建及其光催化性能的研究

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作者：杨晴四川大学

学位级别：硕士

石墨相氮化碳(g-C3N4)具有利于电子传输的平面共轭结构,合适的能带结构,吸收可见光的能力以及可以在酸碱环境中稳定存在。这些性能使它成为了优异的光催化分解水制氢的催化剂。然而,由于它的可见光响应范围较窄,其价带(VB)电位相对较负... 详细信息

石墨相氮化碳(g-C3N4)具有利于电子传输的平面共轭结构,合适的能带结构,吸收可见光的能力以及可以在酸碱环境中稳定存在。这些性能使它成为了优异的光催化分解水制氢的催化剂。然而,由于它的可见光响应范围较窄,其价带(VB)电位相对较负,氧化能力较弱,导致光催化全分解水(产生H2和O2)的效果不理想。钨基含氧化合物(如WO3,Bi2WO6等)是产氧光催化剂。然而,Bi2WO6、WO3半导体依然有对可见光吸收有限、光诱导电荷易于复合、比表面积低等问题。通过掺杂、构建复合物、控制结晶度、缺陷设计、调控晶面等策略,可以优化半导体材料的催化性能。而将用于制氢的催化剂和制氧的催化剂,以及含有氧化还原电对的电子媒介溶液组成Z-型体系,可以同时实现光催化分解水制氢和制氧。本论文工作采用一步合成法制备氮缺陷g-C3N4,通过熔盐合成法控制Bi2WO6、WO3晶面暴露,阻碍了光生电荷重新复合,从而优化了光催化性能。在合适的电子媒介存在下,构建基于g-C3N4的Z-型体系,实现了光催化产氢和产氧。研究内容主要包括:(1)氮缺陷g-C3N4(CN)的制备及光催化产氢活性研究。以硫酸与三聚氰胺反应所得三聚氰胺硫酸盐为原料,通过控制其热聚合升温速率或热解时间来调节g-C3N4中的氮缺陷,研究了含有缺陷的CN在三乙醇胺(TEOA,10 vol%)(2)牺牲试剂以及3%Pt存在下的分解水制氢能力。结果表明,低升温速率或延长热解时间都能将更多的氮空位和末端悬挂氨基引入g-C3N4结构中,从而导致样品光吸收波长红移。此外,缺陷有利于优化g-C3N4催化剂的光催化分解水能力。在升温速率为0.03℃/min或600℃热解125小时,所得样品的产氢活性达到905 μmol·g-1·h-1,是升温速率为1℃/min、600℃下加热4小时条件下合成的g-C3N4活性的2倍。(2)(00l)面暴露单晶Bi2WO6/多晶BiOCl复合物(BWO-PMS)的制备及其光催化性能研究。采用聚四氟乙烯(PTFE)辅助熔盐法(NaCl/KCl)处理化学共沉淀所得前驱体,制备了 BWO-PMS复合光催化剂,对样品进行了形貌结构、光电性能表征,研究了其光生电荷迁移机制。结果表明,BWO-PMS是(006)面暴露的片状单晶Bi2WO6/多晶BiOCl复合物,而采用了无PTFE的熔盐法和固相合成法制备的样品(分别记为BWO-MS和BWO)只有Bi2WO6相。光催化降解RhB结果显示,BWO-PMS的光降解效率分别是BWO-MS、BWO的17倍和70倍。光催化性能提高由于光生电子在BWO-PMS的两种组分间的迁移抑制了光生电荷复合。(3)基于g-C3N4的Z-型光催化剂体系的构建及全分解水性能研究。分别采用溶剂热处理缺陷g-C3N4、4,4,'4"-(1,3,5-三嗪-2,4,6-三基)三苯胺(TA)和2,4,6-三羟基-1,3,5-苯三甲醛(TP)制备了g-C3N4/共价有机框架化合物(COF)复合物(CN-COF)和水热法制备了方形WO3;以CN-COF为产氢光催化剂,WO3、BWO-PMS为用于水氧化的催化剂,加入电子媒介后,形成Z-型光催化剂体系,研究了这个体系的光催化能力。结果表明,CN-COF、WO3(质量比为1:1)和I-/IO3-溶液组成的Z-型体系中分解水的H2产率为13.5 μmol·g-1·h-1,O2产率为5.8μmol·g-1·h-1,H2和O2的物质的量之比为2:1。

关键词： g-C3N4 photocatalytic water splitting defect Bi2WO6 photodegaradation crystal facet

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