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Chinese Journal of Catalysis
2020, Vol. 41, No. 10
Online: 18 October 2020

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Cover: The special issue focuses on the latest experimental and theoretical research advances in environmental photocatalysis, which mainly includes an overview on current research of simultaneous photocatalytic antibiotics degradation and H2 evolution as reported by Shangguan and co-workers, the study that significantly improved photocatalytic activity of ZnO by the modification of Au-Ag alloy for ethylene degradation reported by Huang and co-workers, and the study that greatly improved photocatalytic performance of virus/bacterial inactivation by constructing surficial oxygen vacancies reported by Wang and co-workers.

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Table of Contents for VOL.41 No.10 2020, 41 (10):  0-0.  Abstract ( 24 )   PDF (6421KB) ( 38 )

Editorial

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Special issue: Environmental photocatalysis Liqiang Jing, Chuncheng Chen, Taicheng An 2020, 41 (10):  1439-1439.  DOI: 10.1016/S1872-2067(20)63645-2 Abstract ( 73 )   [Full Text(HTML)] () PDF (385KB) ( 197 )

Reviews

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A review on photocatalysis in antibiotic wastewater: Pollutant degradation and hydrogen production Zhidong Wei, Junying Liu, Wenfeng Shangguan 2020, 41 (10):  1440-1450.  DOI: 10.1016/S1872-2067(19)63448-0 Abstract ( 694 )   [Full Text(HTML)] () PDF (1261KB) ( 929 )   Surveys on antibiotics have become one of the most popular topics in the recent two decades. From 1998 to 2018, more than 5,000 articles concentrated on the research of antibiotic wastewater treatment have been published. Among them, photocatalysis has received much attention due to its green and environmental-friendly properties. In this mini-review, the recent progress of photocatalysis in antibiotic wastewater was summarized, including antibiotics degradation and hydrogen energy conversion. The photocatalysts commonly used were also discussed. It can be mainly classified as TiO2-based materials, sulfides and polymeric carbon nitride-based materials and bismuth-contained materials. Four major types of antibiotics, tetracycline, sulfonamide, β-lactam and quinolone, were involved. Furthermore, perspectives concentrated on future development and challenges, especially converting antibiotics into hydrogen energy, were also proposed.

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Effects of fluorine on photocatalysis Xiaofang Li, Xiaofeng Wu, Shengwei Liu, Yuhan Li, Jiajie Fan, Kangle Lv 2020, 41 (10):  1451-1467.  DOI: 10.1016/S1872-2067(20)63594-X Abstract ( 223 )   [Full Text(HTML)] () PDF (1756KB) ( 560 )   Tailoring the microstructure of pristine TiO2 is essential to narrow its band gap and prolong the charge lifetime. In particular, strategies involving fluorine have been used successfully to tune the surface chemistry, electronic structure, and morphology of TiO2 photocatalysts to improve their photocatalytic activity based on the strong complexation between fluoride ions and TiO2 and the high electronegativity of fluorine. In this review, we summarize the strategies involving fluorine to establish highly efficient TiO2 photocatalytic systems or fabricate highly efficient TiO2 photocatalysts. The main fluorine effects (i.e. the effects of fluorine on photocatalysis) include the following four aspects:(1) Surface effects of fluoride on TiO2 photocatalysis, (2) effects of fluorine doping on TiO2 photocatalysis, (3) fluoride-mediated tailoring of the morphology of TiO2 photocatalysts, and (4) the effects of fluorine on non-TiO2 photocatalysis. Additionally, the unique applications of these fluorine effects in photocatalysis, including selective degradation of pollutants, selective oxidation of chemicals, water-splitting to produce H2, reduction of CO2 to produce solar fuels, and improvement of the thermostability of TiO2 photocatalysts, are reviewed.

Communications

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Visible-light photocatalytic selective aerobic oxidation of thiols to disulfides on anatase TiO2 Hui Xu, Ji-Long Shi, Shaoshuai Lyu, Xianjun Lang 2020, 41 (10):  1468-1473.  DOI: 10.1016/S1872-2067(20)63640-3 Abstract ( 122 )   [Full Text(HTML)] () PDF (511KB) ( 283 )   Supporting Information This work presents the visible-light photocatalytic selective oxidation of thiols to disulfides with molecular oxygen (O2) on anatase TiO2. The high specific surface area of anatase TiO2 proved to be especially critical in conferring high photocatalytic activity. Herein, surface complexation between thiol and TiO2 gives rise to photocatalytic activity under irradiation with 520 nm green light-emitting diodes (LEDs), resulting in excellent reaction activity, substrate scope, and functional group tolerance. The transformation was extremely efficient for the selective oxidation of various thiols, particularly with substrates bearing electron-withdrawing groups (reaction times of less than 10 min). To date, the longest wavelength of visible light that this system can utilize is 520 nm by the surface complex of substrate-TiO2. Importantly, O2 was found to act as the electron and proton acceptor, rather than to incorporate into the substrates. Our findings regarding this surface complex-based photocatalytic system can allow one to understand the interaction between the conduction band electrons and O2.

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Light-driven activation of carbon-halogen bonds by readily available amines for photocatalytic hydrodehalogenation Di Meng, Qian Zhu, Yan Wei, Shengli Zhen, Ran Duan, Chuncheng Chen, Wenjing Song, Jincai Zhao 2020, 41 (10):  1474-1479.  DOI: 10.1016/S1872-2067(20)63582-3 Abstract ( 319 )   [Full Text(HTML)] () PDF (533KB) ( 550 )   Supporting Information A straightforward protocol using readily available aromatic amines, N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine, as photocatalysts was developed for the efficient hydrodehalogenation of organic halides, such as 4'-bromoacetophenone, polyfluoroarenes, cholorobenzene, and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollutant). The strongly reducing singlet excited states of the amines enabled diffusion-controlled dissociative electron transfer to effectively cleave carbon-halogen bonds, followed by radical hydrogenation. Diisopropylethylamine served as the terminal electron/proton donor and regenerated the amine sensitizers.

Articles

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Molecular oxygen activation enhancement by BiOBr0.5I0.5/BiOI utilizing the synergistic effect of solid solution and heterojunctions for photocatalytic NO removal Mingpu Kou, Yu Deng, Rumeng Zhang, Li Wang, Po Keung Wong, Fengyun Su, Liqun Ye 2020, 41 (10):  1480-1487.  DOI: 10.1016/S1872-2067(20)63607-5 Abstract ( 197 )   [Full Text(HTML)] () PDF (1149KB) ( 253 )   Supporting Information To improve the photocatalytic oxidation reaction activity for NO removal, photocatalysts with excellent activity are required to activate molecular oxygen. Solid solution and heterojunction were suggested as effective strategies to enhance the molecular oxygen activation viaexciton and carrier photocatalysis. In this study, a solid solution and heterojunction containing BiOBr0.5I0.5/BiOI catalyst was synthesized, and it showed improved photocatalytic activity for removing NO. The photocatalytic NO removal mechanism indicated that synergistic effects between the solid solution and heterojunction induced the enhanced activity for molecular oxygen activation. The photogenerated holes, superoxide, and singlet oxygen generated by the carrier and exciton photocatalysis supported the high photocatalytic NO removal efficiency. This study provides new ideas for designing efficient Bi-O-X (X=Cl, Br, I) photocatalysts for oxidation reactions.

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Microwave-assisted synthesis of defective tungsten trioxide for photocatalytic bacterial inactivation: Role of the oxygen vacancy Wenquan Gu, Wanjun Wang, Guiying Li, Haojing Xie, Po Keung Wong, Taicheng An 2020, 41 (10):  1488-1497.  DOI: 10.1016/S1872-2067(19)63409-1 Abstract ( 239 )   [Full Text(HTML)] () PDF (1724KB) ( 437 )   Supporting Information Surface defect modulation has emerged as a potential strategy for promoting the photocatalytic activity of photocatalysts for various applications, while the impact of the oxygen vacancy on bacterial inactivation is still debated. In this study, oxygen vacancies were introduced to tungsten trioxide nanosheets (WO3-x) via a microwave-assisted route. The as-prepared WO3-x nanosheets exhibited excellent visible-light-driven photocatalytic activity toward E. coli K-12 inactivation, and 6 log orders of the bacterial cells could be completely inactivated within 150 min. The obtained bacterial inactivation rate constant was 15.2 times higher than that of pristine WO3 without oxygen vacancies, suggesting that the surface oxygen vacancy could significantly promote the bacterial inactivation efficiency. The mechanism study indicated that the inactivation of bacterial cells occurs via a direct h+ oxidation pathway. In addition, the role of the oxygen vacancy was studied in detail; the oxygen vacancy was found to not only promote interfacial charge separation but also tune the band structure of WO3, thereby leading to increased h+ oxidation power. Finally, a possible oxygen vacancy-dominated photocatalytic bacterial inactivation mechanism is proposed. This work is expected to offer new insights into the microwave-assisted synthesis of defective photocatalysts and the use of the oxygen vacancy for promoting photocatalytic antibacterial activities.

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Br-doping of g-C3N4 towards enhanced photocatalytic performance in Cr(VI) reduction Mian Wang, Yubin Zeng, Guohui Dong, Chuanyi Wang 2020, 41 (10):  1498-1510.  DOI: 10.1016/S1872-2067(19)63435-2 Abstract ( 157 )   [Full Text(HTML)] () PDF (966KB) ( 346 )   Semiconductor photocatalytic technology is widely recognized as one of the most promising technologies to solve current energy and environmental crisis, due to its ability to make effective use of solar energy. In recent years, graphite carbon nitride (g-C3N4), a new type of non-metallic polymer semiconductor photocatalyst, has rapidly become the focus of intense research in the field of photocatalysis because of its suitable bandgap energy, unique structure, and excellent chemical stability. In order to improve its intrinsic shortages of small specific surface area, narrow visible light response range, high electron-hole pair recombination rate, and low photon quantum efficiency, a simple method was utilized to synthesize Br-doped g-C3N4 (CN-BrX, X=5, 10, 20, 30), where X is a percentage mole ratio of NH4Br to melamine. Experimental results showed that Br atoms were doped into the g-C3N4 lattice by replacing the bonded N atoms in the form of C-N=C, while the derived material retained the original framework of g-C3N4. The interaction of Br element with the g-C3N4 skeleton not only broadened the visible-light response of g-C3N4 to 800 nm with an adjustable band gap, but also greatly promoted the separation efficiency of the photogenerated charge carrier and the surface area. The photocurrent intensity of bare CN and CN-BrX (X=5, 10, 20, 30) catalysts is calculated to be 1.5, 2.0, 3.1, 6.5, and 1.9 μA, respectively. And their specific surface area is measured to be 9.086, 9.326, 15.137, 13.397, and 6.932 m2/g. As a result, this Br-doped g-C3N4 gives significantly enhanced photocatalytic reduction of Cr(VI), achieving a twice enhancement over g-C3N4, with high stability during prolonged photocatalytic operation compared to bare g-C3N4 under visible light irradiation. Furthermore, an underlying photocatalytic reduction mechanism was proposed based on control experiments using radical scavengers.

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Significant role of carbonate radicals in tetracycline hydrochloride degradation based on solar light-driven TiO2-seashell composites: Removal and transformation pathways Jiaqi Wang, Qingrong Qian, Qinghua Chen, Xin-Ping Liu, Yongjin Luo, Hun Xue, Zhaohui Li 2020, 41 (10):  1511-1521.  DOI: 10.1016/S1872-2067(19)63525-4 Abstract ( 115 )   [Full Text(HTML)] () PDF (1065KB) ( 215 )   TiO2-seashell composites prepared via a sol-gel method were used to generate carbonate radicals (·CO3-) under solar light irradiation.·CO3-, a selective radical, was employed to degrade the target tetracycline hydrochloride contaminant. A series of characterizations was carried out to study the structure and composition of the synthesized TiO2-seashell composite. This material exhibits excellent solar light-driven photochemical activity in the decomposition of tetracycline hydrochloride. The possible pathway and mechanism for the photodegradation process were proposed on the basis of high-resolution electrospray ionization time-of-flight mass spectrometry experiments. Finally, we investigated the reusability of the TiO2-seashell composite. This study is expected to provide a new facile pathway for the application of·CO3- radicals to degrade special organic pollutants in water.

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Experimental method to explore the adaptation degree of type-II and all-solid-state Z-scheme heterojunction structures in the same degradation system Zheao Huang, Shuo Zhao, Ying Yu 2020, 41 (10):  1522-1534.  DOI: 10.1016/S1872-2067(19)63495-9 Abstract ( 549 )   [Full Text(HTML)] () PDF (1155KB) ( 396 )   TiO2 nanoparticles were prepared using the hydrothermal method and modified with C3N4 to synthesize a Type-II heterojunction semiconductor photocatalyst, TiO2-C3N4. In addition, a carbon layer was coated onto the TiO2 nanoparticles and the obtained material was uniformly covered on the surface of C3N4 to form an all-solid-state Z-scheme semiconductor photocatalyst, TiO2-C-C3N4. Through characterization by XRD, XPS, SEM, TEM, BET, photoelectrochemical experiments, UV-visible diffuse reflection, and PL spectroscopy, the charge transfer mechanism and band gap positions for the composite photocatalysts were analyzed. The Type-II and all-solid-state Z-scheme heterojunction structures were compared. By combining microscopic internal mechanisms with macroscopic experimental phenomena, the relationship between performance and structure was verified. Experimental methods were used to explore the adaptation degree of different photocatalytic mechanisms using the same degradation system. This study highlights effective photocatalyst design to meet the requirements for specific degradation conditions.

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Preparation of BiOCl0.9I0.1/β-Bi2O3 composite for degradation of tetracycline hydrochloride under simulated sunlight Xiong Ma, Kaiyi Chen, Bin Niu, Yan Li, Lei Wang, Jingwei Huang, Houde She, Qizhao Wang 2020, 41 (10):  1535-1543.  DOI: 10.1016/S1872-2067(19)63486-8 Abstract ( 149 )   [Full Text(HTML)] () PDF (3187KB) ( 333 )   Supporting Information A novel and effective BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst was synthesized through a precipitation method. The structure, morphology, and optical properties of the samples were certified by X-ray diffraction, UV-Vis diffuse reflectance, scanning electron microscopy, and X-ray photoelectron spectroscopic characterizations. Photocatalytic experiments demonstrated that the synthesized BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst exhibited excellent photocatalytic performance toward the degradation of tetracycline hydrochloride (TCH) under simulated sunlight. Furthermore, the TCH degradation rate of BiOCl0.9I0.1/15%β-Bi2O3 increased by 27.6% and 61.4% compared with those of the pure BiOCl0.9I0.1 and pure β-Bi2O3, respectively. Due to the multiple vacancies and valence states possessed by BiOCl0.9I0.1/x%β-Bi2O3, namely Bi5+, Bi(3-x)+, Bi5+-O, Bi3+-O, I- and I3-, the charge separation in photocatalysis reactions can be effectively promoted. The Mott-Schottky measurements indicate that the conduction band (CB) level of BiOCl0.9I0.1/15%β-Bi2O3 becomes more negative relative to that of BiOCl0.9I0.1, guaranteeing an advantageous effect on the redox ability of the photocatalyst. This study provides a new bright spot for the construction of high-performance photocatalysts.

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Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization Shengyao Wang, Zhongliang Xiong, Nan Yang, Xing Ding, Hao Chen 2020, 41 (10):  1544-1553.  DOI: 10.1016/S1872-2067(19)63506-0 Abstract ( 288 )   [Full Text(HTML)] () PDF (1244KB) ( 308 )   In this work, the tunable introduction of oxygen vacancies in bismuth tungstate was realized via a simple solvothermal method with the assistance of iodine doping. With the predictions afforded by theoretical calculations, the as-prepared bismuth tungstate was characterized using various techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The different concentrations of the oxygen vacancies on bismuth tungstate were found to be intensely correlated with iodine doping, which weakened the lattice oxygen bonds. Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as a result of iodine doping, the molecular oxygen activation was remarkably enhanced, thus endowing bismuth tungstate with high activity for the photocatalytic degradation of sodium pentachlorophenate. More encouraging is the total organic carbon removal rate of sodium pentachlorophenate over iodine-doped bismuth tungstate that exceeded 90% in only 2 h and was 10.6 times higher than that of the pristine bismuth tungstate under visible light irradiation. Moreover, the mechanism, through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tungstate is enhanced, was speculated based on the results of radical detection and capture experiments. This work provides a new perspective for the enhanced photocatalytic degradation of organochlorine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-doped bismuth tungstate.

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In-situ fabrication SnO2/SnS2 heterostructure for boosting the photocatalytic degradation of pollutants Ying Liu, Donglai Pan, Mingwen Xiong, Ying Tao, Xiaofeng Chen, Dieqing Zhang, Yu Huang, Guisheng Li 2020, 41 (10):  1554-1563.  DOI: 10.1016/S1872-2067(19)63498-4 Abstract ( 132 )   [Full Text(HTML)] () PDF (3015KB) ( 290 )   Supporting Information Heterostructure photocatalysts with a built-in electric field have become one of the most promising strategies to enhance photogenerated electron-hole pair separation. However, close contact between the two active components of heterogeneous photocatalysts remains a problem. Herein, the in-situ fabrication of an SnO2/SnS2 heterostructure photocatalyst was performed; the structure showed enhanced photocatalytic performance resulting from the tight-contact heterostructures. The results of photoelectrochemical measurements further verified that a tight-contact heterostructure improved the separation of photogenerated electron-hole pairs. The results of EIS Bode plots also demonstrated that such in-situ fabricated SnO2/SnS2 samples exhibited the longest carrier lifetime (41.6 μs) owing to the intimate interface of SnO2/SnS2 heterostructures.

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The photocatalytic performance and active sites of g-C3N4 effected by the coordination doping of Fe(III) Guimei Liu, Guohui Dong, Yubin Zeng, Chuanyi Wang 2020, 41 (10):  1564-1572.  DOI: 10.1016/S1872-2067(19)63518-7 Abstract ( 107 )   [Full Text(HTML)] () PDF (881KB) ( 383 )   Element doping is a simple and effective method to improve photocatalytic activity of g-C3N4. However, the doping model and mechanism of metal elements are still uncharacterized. In this study, we found that Fe(III) can be doped into g-C3N4 through the coordination between amidogen and Fe(III). After activity tests, it was found that this coordination doping of Fe(III) could enhance the RhB oxidation and Cr(VI) reduction activities of g-C3N4 in interesting ways, but it is not helpful for the NO-removal performance of g-C3N4. Characterization and calculation results show that the coordination of Fe(III) can not only improve the transfer of photogenerated electrons, but it also can passivate the carbon site of triazine rings, which is the active site of NO-removal. This study revealed some doping mechanisms and effect mechanisms of elemental metal in photocatalysis.

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Thermo-responsive functionalized PNIPAM@Ag/Ag3PO4/CN-heterostructure photocatalyst with switchable photocatalytic activity Linlin Sun, Yaju Zhou, Xin Li, Jinze Li, Dong Shen, Shikang Yin, Huiqin Wang, Pengwei Huo, Yongsheng Yan 2020, 41 (10):  1573-1588.  DOI: 10.1016/S1872-2067(20)63554-9 Abstract ( 120 )   [Full Text(HTML)] () PDF (5047KB) ( 402 )   It is extremely important for photocatalysts to exhibit intelligent responsiveness to their environment. Herein, a poly N-isopropyl acrylamide (PNIPAM)-modified Ag/Ag3PO4-20/CN hybrid material with excellent convertible photocatalytic activity is prepared. PNIPAM has good hydrophilicity below the lower critical solution temperature (LCST); this increases the capacity of the photocatalyst for adsorbing tetracycline (TC) molecules. In addition, the PNIPAM-modified Ag/Ag3PO4-20/CN can prevent the loss of Ag3PO4. The dispersity is improved by loading g-C3N4 nanosheets (CN) for enhancing the efficiency of photocatalytic activity. Furthermore, a Z-scheme heterostructure is formed between CN and Ag3PO4, accelerating the separation efficiency of the holes and electrons. Ag nanoparticles can be used as electron-shuttle mediators, and electrons receiving more energy are transferred via the localized surface plasmon resonance (LSPR) effect. Furthermore, the PNIPAM@Ag/Ag3PO4-20/CN photocatalyst exhibits an excellent degradation rate for the degradation of TC when the temperature is lower than the LCST. The photoluminescence spectra and photocurrent curves prove that the carrier-separation efficiency of PNIPAM@Ag/Ag3PO4-20/CN is higher than those of Ag/Ag3PO4/CN and CN. The main active species of·O2- and h+ are detected to reveal the plausible mechanism of the PNIPAM@Ag/Ag3PO4-20/CN hybrid material system. This work provides a way to develop intelligent materials for switchable photocatalytic applications.

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Synthesis of Ni2+ cation modified TS-1 molecular sieve nanosheets as effective photocatalysts for alcohol oxidation and pollutant degradation Imran Khan, Xiaoyu Chu, Yanduo Liu, Salman Khan, Linlu Bai, Liqiang Jing 2020, 41 (10):  1589-1602.  DOI: 10.1016/S1872-2067(20)63555-0 Abstract ( 165 )   [Full Text(HTML)] () PDF (1130KB) ( 452 )   Supporting Information Improvement of the charge separation of titanosilicate molecular sieves is critical to their use as photocatalysts for oxidative organic transformations. In this work, MFI TS-1 molecular sieve nanosheets (TS-1 NS) were synthesized by a low-temperature hydrothermal method using a tailored diquaternary ammonium surfactant as the structure-directing agent. Introducing Ni2+ cations at the ion-exchange sites of the TS-1 NS framework signi?cantly enhanced its photoactivity in aerobic alcohol oxidation. The optimized Ni cation-functionalized TS-1 NS (Ni/TS-1 NS) provide impressive photoactivity, with a benzyl alcohol (BA) conversion of 78.9% and benzyl aldehyde (BAD) selectivity of 98.8% using O2 as the only oxidant under full light irradiation; this BAD yield is approximately six times greater than that obtained for bulk TS-1, and is maintained for five runs. The excellent photoactivity of Ni/TS-1 NS is attributed to the significantly enlarged surface area of the two-dimensional morphology TS-1 NS, extra mesopores, and greatly improved charge separation. Compared with bulk TS-1, Ni/TS-1 NS has a much shorter charge transfer distance. The as-introduced Ni species could capture the photoelectrons to further improve the charge separation. This work opens the way to a class of highly selective, robust, and low-cost titanosilicate molecular sieve-based photocatalysts with industrial potential for selective oxidative transformations and pollutant degradation.

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In-situ decoration of metallic Bi on BiOBr with exposed (110) facets and surface oxygen vacancy for enhanced solar light photocatalytic degradation of gaseous n-hexane Qingqing Yu, Jiangyao Chen, Yanxu Li, Meicheng Wen, Hongli Liu, Guiying Li, Taicheng An 2020, 41 (10):  1603-1612.  DOI: 10.1016/S1872-2067(19)63496-0 Abstract ( 127 )   [Full Text(HTML)] () PDF (1159KB) ( 282 )   Supporting Information Photocatalytic degradation of gaseous pollutants on Bi-based semiconductors under solar light irradiation has attracted significant attention. However, their application in gaseous straight-chain alkane purification is still rare. Here, a series of Bi/BiOBr composites were solvothermally synthesized and applied in solar-light-driven photocatalytic degradation of gaseous n-hexane. The characterization results revealed that both increasing number of functional groups of alcohol solvent (from methanol and ethylene glycol to glycerol) and solvothermal temperature (from 160 and 180 to 200℃) facilitated the in-situ formation of metallic Bi nanospheres on BiOBr nanoplates with exposed (110) facets. Meanwhile, chemical bonding between Bi and BiOBr was observed on these exposed facets that resulted in the formation of surface oxygen vacancy. Furthermore, the synergistic effect of optimum surface oxygen vacancy on exposed (110) facets led to a high visible light response, narrow band gap, great photocurrent, low recombination rate of the charge carriers, and strong·O2- and h+ formation, all of which resulted in the highest removal efficiency of 97.4% within 120 min of 15 ppmv of n-hexane on Bi/BiOBr. Our findings efficiently broaden the application of Bi-based photocatalysis technology in the purification of gaseous straight-chain pollutants emitted by the petrochemical industry.

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ZnO nanorod decorated by Au-Ag alloy with greatly increased activity for photocatalytic ethylene oxidation Huishan Zhai, Xiaolei Liu, Zeyan Wang, Yuanyuan Liu, Zhaoke Zheng, Xiaoyan Qin, Xiaoyang Zhang, Peng Wang, Baibiao Huang 2020, 41 (10):  1613-1621.  DOI: 10.1016/S1872-2067(19)63473-X Abstract ( 165 )   [Full Text(HTML)] () PDF (1380KB) ( 414 )   Supporting Information In recent years, the preservation of fruits and vegetables in cold storage has become an issue of increasing concern, ethylene plays a leading role among them. We found ZnO has the effect of degrading gaseous ethylene, however its effect is not particularly satisfactory. Therefore, we used simple photo-deposition procedure and low-temperature calcination method to synthesize Au, Ag, and AuAg alloy supported ZnO to improve the photocatalytic efficiency. Satisfactorily, after ZnO loaded with sole Au or Ag particles, the efficiency of ethylene degradation was 17.5 and 26.8 times than that of pure ZnO, showing a large increase in photocatalytic activity. However, the photocatalytic stability of Ag/ZnO was very poor, because Ag can be easily photooxidized to Ag2O. Surprisingly, when ZnO was successfully loaded with the AuAg alloy, not only the photocatalytic activity was further improved to 94.8 times than that of pure ZnO, but also the photocatalytic stability was very good after 10 times of cycles. Characterization results explained that the Au-Ag alloy NPs modified ZnO showed great visible-light absorption because of the surface plasmon resonance (SPR) effect. Meanwhile, the higher photocurrent density showed the effective carrier separation ability in AuAg/ZnO. Therefore, the cooperative action of plasmonic AuAg bimetallic alloy NPs and efficient carrier separation capability result in the outstanding photoactivity of ethylene oxidation. At the same time, the formation of the alloy produced a new crystal structure different from Au and Ag, which overcomes the problem of poor stability of Ag/ZnO, and finally obtains AuAg/ZnO photocatalyst with high activity and high stability. This work proposes a new concept of using metal alloys to remove ethylene in actual production.

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High-humidity tolerance of porous TiO2(B) microspheres in photothermal catalytic removal of NOx He Ma, Changhua Wang, Songmei Li, Xintong Zhang, Yichun Liu 2020, 41 (10):  1622-1632.  DOI: 10.1016/S1872-2067(19)63508-4 Abstract ( 109 )   [Full Text(HTML)] () PDF (1424KB) ( 283 )   Semiconductor oxides are widely used to achieve photocatalytic removal of NOx (NO and NO2) species. These materials also exhibit enhanced oxidation ability in thermally assisted photocatalysis; however, many of them tend to be deactivated at high relative humidity (RH) levels. In the case of the benchmark P25 TiO2 photocatalyst, we observe a significant decrease in non-NO2 selectivity from 95.02% to 58.33% when RH increases from 20% to 80%. Interestingly, the porous TiO2(B) microspheres synthesized in this work exhibit 99% selectivity at 20% RH; the selectivity remains as high as 96.18% at 80% RH. The high humidity tolerance of the TiO2(B) sample can be ascribed to its strong water desorption capacity and easy O2 adsorption at elevated temperatures, which reflects the fact that the superoxide radical is the main active species for the deep oxidation of NOx. This work may inspire the design of efficient photothermal catalysts with application in NOx removal in hot and humid environments.

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Density functional theory calculations on single atomic catalysis: Ti-decorated Ti3C2O2 monolayer (MXene) for HCHO oxidation Junhui Zhou, Guanlan Liu, Quanguo Jiang, Weina Zhao, Zhimin Ao, Taicheng An 2020, 41 (10):  1633-1644.  DOI: 10.1016/S1872-2067(20)63571-9 Abstract ( 166 )   [Full Text(HTML)] () PDF (984KB) ( 523 )   Supporting Information Formaldehyde (HCHO) is a common indoor pollutant, long-term exposure to HCHO may harm human health. Its efficient removal at mild conditions is still challenging. The catalytic oxidation of HCHO molecules on a single atomic catalyst, Ti-decorated Ti3C2O2 (Ti/Ti3C2O2) monolayer, is investigated by performing the first principles calculations in this work. It demonstrates that Ti atoms can be easily well dispersed at the form of single atom on Ti3C2O2 monolayer without aggregation. For HCHO catalytic oxidation, both Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms are considered. The results show that the step of HCHO dissociative adsorption on Ti/Ti3C2O2 with activated O2 can release high energy of 4.05 eV based on the ER mechanism, which can help to overcome the energy barrier (1.04 eV) of the subsequent reaction steps. The charge transfer from *OH group to CO molecule (dissociated from HCHO) not only promotes *OH group activation but also plays an important role in the H2O generation along the ER mechanism. Therefore, HCHO can be oxidized easily on Ti/Ti3C2O2 monolayer, this work could provide significant guidance to develop effective non-noble metal catalysts for HCHO oxidation and broaden the applications of MXene-based materials.

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Facile synthesis and photoelectrochemical properties of novel TiN/C3N4/CdS nanotube core/shell arrays Changzhi Ai, Li Tong, Zhipeng Wang, Xidong Zhang, Guizhen Wang, Shengjue Deng, Jin Li, Shiwei Lin 2020, 41 (10):  1645-1653.  DOI: 10.1016/S1872-2067(19)63512-6 Abstract ( 114 )   [Full Text(HTML)] () PDF (702KB) ( 286 )   Supporting Information Recently, the g-C3N4-based heterojunctions have been widely investigated for their greatly enhanced photogenerated carrier separation efficiency. However, most studies are based on the study of g-C3N4 powders. In this study, a novel TiN/C3N4/CdS nanotube arrays core/shell structure is designed to improve the photoelectrochemical catalytic performance of the g-C3N4-based heterojunctions. Among them, TiN nanotube arrays do not respond to simulated solar light, and thus only serve as an excellently conductive nanotube arrays backbone for supporting g-C3N4/CdS heterojunctions. g-C3N4 prepared by simple liquid atomic layer deposition, which possesses appropriate energy band position, mainly acts as the electron acceptor to transport and separate electrons. Deposited CdS quantum dots obtained by successive ionic layer adsorption reaction can effectively absorb visible light and thus act as a light absorber. The TiN/C3N4/CdS nanotube arrays core/shell structure could be verified by X-ray diffractions, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy elemental mappings and X-ray photoelectron spectroscopy. Compared with TiN/C3N4 nanotube arrays, the TiN/C3N4/CdS samples greatly improve the photoelectrochemical performance, which can be evaluated by photoelectrochemical tests and photoelectrochemical catalytic degradation. Especially, the optimized photocurrent density of TiN/C3N4/CdS has almost 120 times improvement on TiN/C3N4 at 0 V bias under simulated sunlight, which can be ascribed to the effective expansion of the light absorption range and separation of electron-hole pairs.

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Hierarchical cobalt phenylphosphonate nanothorn flowers for enhanced electrocatalytic water oxidation at neutral pH Mei-Rong Liu, Yang-Peng Lin, Kai Wang, Shumei Chen, Fei Wang, Tianhua Zhou 2020, 41 (10):  1654-1662.  DOI: 10.1016/S1872-2067(19)63513-8 Abstract ( 138 )   [Full Text(HTML)] () PDF (666KB) ( 274 )   Supporting Information Cobalt-based phosphate/phosphonates are a class of promising water oxidation catalysts at neutral pH. Herein, we reported a facile hydrothermal synthesis of various nanostructured cobalt phenylphosphonates. It is found that the number of hydroxyl group of structure-directing reagent is crucial for the construction of 3D hierarchical structures including hierarchical nanosheet flower-like assemblies and nanothorn microsphere. These samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared, and X-ray photoelectron spectroscopy techniques. They can act as highly efficient electrocatalysts for the oxygen evolution reaction at neutral pH. Among these, hierarchical cobalt phenylphosphonate nanothorn flowers present excellent performance, affording a current density of 1 mA cm-2 required a small overpotential of 393 mV. This work offers a new clue to develop high-performance metal phosphonate/phosphate catalysts toward electrochemical water oxidation.

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Composition-tunable ZnS1-xSex nanobelt solid solutions for efficient solar-fuel production Pan Li, Sajjad Hussain, Lu Li, Lingju Guo, Tao He 2020, 41 (10):  1663-1673.  DOI: 10.1016/S1872-2067(20)63537-9 Abstract ( 71 )   [Full Text(HTML)] () PDF (1334KB) ( 202 )   Supporting Information Band engineering based on the construction of solid solutions is an effective approach to enhance the efficiency of semiconductor photocatalysts, via which the balance between light absorption and driving force can be well achieved by continuously tuning the band structure. Here the ZnS1-xSex nanobelt solid solutions have been prepared via thermal treatment of ZnS1-xSex(en)0.5 precursors. The compositions are adjusted by changing the mole ratio of Se to S powder in the starting materials, resulting in continuously modulating the alignment of energy levels of the obtained solid solutions. The band structure is also studied via theoretical calculation. Accordingly, the light harvesting can be tuned too, as confirmed by the UV-vis absorption spectra. XPS valence spectra are used to determine the valence band maximum. Transient photoluminescence spectra are employed to study the separation of photogenerated charge carriers. BET specific surface area and CO2 adsorption isotherms of different catalysts are measured. The obtained ZnS1-xSex nanobelts exhibit different photocatalytic activity for solar-fuel production, dependent on many factors like the light harvesting and alignment of energy levels. The related mechanism is studied in detail.

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Pyroelectricity effect on photoactivating palladium nanoparticles in PbTiO3 for Suzuki coupling reaction Jieya Wen, Lili Ling, Yao Chen, Zhenfeng Bian 2020, 41 (10):  1674-1681.  DOI: 10.1016/S1872-2067(20)63581-1 Abstract ( 188 )   [Full Text(HTML)] () PDF (836KB) ( 323 )   Supporting Information Combining microwave radiation with photocatalytic systems is a promising method to inhibit photogenerated electron-hole recombination and enhance the photocatalytic reaction performance. In this study, we have designed Pd/PbTiO3 catalysts that can use both microwave fields and photocatalysis. Benefiting from the synergistic effect of microwave field and UV light, the PbTiO3 crystals convert thermal energy into electrical energy via the pyroelectricity effect, generating positive and negative charges (q+ and q-), while Pd nanoparticles significantly improve the quantum efficiency of the photocatalytic process. The composite catalyst significantly enhances the reaction rate and selectivity of the model Suzuki coupling reaction performed with bromobenzene. Microwave fields can directly act on chemical systems, promoting or changing various chemical reactions in unique ways.