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Chinese Journal of Catalysis
2019, Vol. 40, No. 5
Online: 18 May 2019


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The Bi₂O₂CO₃ absorbs only UV light and has a high carrier recombination rate, which limits the overall visible light photocatalytic efficiency in environmental remediation. Prof. Dong and co-authors used in situ DRIFTS spectra combined with ESR spectra and DFT calculation to reveal the electronic structure of oxygen vacancy and the conversion pathway of photocatalytic NO oxidation on defective Bi₂O₂CO₃. The results show that oxygen vacancies can increase the generation of active radicals and promote the conversion of NO to target products rather than toxic by-products (NO₂), thus greatly improving the selectivity. This work could provide new strategies for improving photocatalytic selectivity and understanding the gas-phase reaction mechanism (see pages 620–630).

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Table of Contents for VOL.40 No.5 2019, 40 (5):  0-0.  Abstract ( 82 )   PDF (1710KB) ( 277 )

Editorial

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Preface to Special Issue on Environmental and Energy Catalysis for Sustainable Development Fan Dong, Ying Zhou, Guidong Yang 2019, 40 (5):  619-619.  DOI: 10.1016/S1872-2067(19)63351-6 Abstract ( 161 )   [Full Text(HTML)] () PDF (176KB) ( 312 )

Articles

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Pivotal roles of artificial oxygen vacancies in enhancing photocatalytic activity and selectivity on Bi2O2CO3 nanosheets Hongjing Liu, Peng Chen, Xiaoya Yuan, Yuxin Zhang, Hongwei Huang, Li'ao Wang, Fan Dong 2019, 40 (5):  620-630.  DOI: 10.1016/S1872-2067(19)63279-1 Abstract ( 341 )   [Full Text(HTML)] () PDF (908KB) ( 794 )   Supporting Information There is an increasing interest in bismuth carbonate (Bi2O2CO3, BOC) as a semiconductor photocatalyst. However, pure BOC strongly absorbs ultraviolet light, which drives a high recombination rate of charge carriers and thereby limits the overall photocatalysis efficiency. In this work, artificial oxygen vacancies (OV) were introduced into BOC (OV-BOC) to broaden the optical absorption range, increase the charge separation efficiency, and activate the reactants. The photocatalytic removal ratio of NO was increased significantly from 10.0% for pure BOC to 50.2% for OV-BOC because of the multiple roles played by the oxygen vacancies. These results imply that oxygen vacancies can facilitate the electron exchange between intermediates and the surface oxygen vacancies in OV-BOC, making them more easily destroyed by active radicals. In situ DRIFTS spectra in combination with electron spin resonance spectra and density functional theory calculations enabled unraveling of the conversion pathway for the photocatalytic NO oxidation on OV-BOC. It was found that oxygen vacancies could increase the production of active radicals and promote the transformation of NO into target products instead of toxic byproducts (NO2), thus the selectivity is significantly enhanced. This work provides a new strategy for enhancing photocatalytic activity and selectivity.

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Ordered mesoporous Fe/TiO2 with light enhanced photo-Fenton activity Zhenmin Xu, Ru Zheng, Yao Chen, Jian Zhu, Zhenfeng Bian 2019, 40 (5):  631-637.  DOI: 10.1016/S1872-2067(19)63309-7 Abstract ( 213 )   [Full Text(HTML)] () PDF (681KB) ( 560 )   Ordered mesoporous Fe/TiO2 was prepared by an evaporation-induced self-assembly method. The iron ions were in situ embedded in the pore wall of the TiO2 framework. The catalyst has excellent light-assisted Fenton catalytic performance under UV and visible light irradiation. X-ray diffraction and transmission electron microscopy results showed that the TiO2 samples have an ordered two-dimensional hexagonal pore structure and an anatase phase structure with high crystallinity. The ordered pore structure of the TiO2 photocatalyst with a large specific surface area is beneficial to mass transfer and light harvesting. Furthermore, iron ions can be controlled by embedding them into the TiO2 framework to prevent iron ion loss and inactivation. After five cycles, the reaction rate of the ordered mesoporous Fe/TiO2 remained unchanged, indicating that the material has stable performance and broad application prospects for the purification of environmental pollutants.

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Structural effect and reaction mechanism of MnO2 catalysts in the catalytic oxidation of chlorinated aromatics Xiaole Weng, Yu Long, Wanglong Wang, Min Shao, Zhongbiao Wu 2019, 40 (5):  638-646.  DOI: 10.1016/S1872-2067(19)63322-X Abstract ( 263 )   [Full Text(HTML)] () PDF (714KB) ( 807 )   Supporting Information Various MnO2 structures have been extensively applied in catalysis. In this study, γ-MnO2, α-MnO2, and δ-MnO2 with corresponding rod, tube, and hierarchical architecture morphologies were prepared and applied for the catalytic oxidation of chlorobenzene (CB). The redox ability, H2O activation behavior, and acidity of MnO2 were analyzed using a range of techniques, including TPR, H2O-TPD, XPS, and pyridine-IR. The catalytic activities in CB oxidation were assessed; this revealed that γ-MnO2 exhibited the highest activity and best stability, owing to its enriched surface oxygen vacancies that functioned to activate O2 and H2O, and capture labile chlorine, which reacted with dissociated H2O to form HCl. All the MnO2 phases generated toxic polychlorinated by-products, including CHCl3, CCl4, C2HCl3, and C2Cl4, indicating the occurrence of electrophilic chlorination during CB oxidation. In particular, the dichlorobenzene detected in the effluents of α-MnO2 might generate unintended dioxins via a nucleophilic substitution reaction.

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The pivotal effects of oxygen vacancy on Bi2MoO6: Promoted visible light photocatalytic activity and reaction mechanism Yanjuan Sun, Hong Wang, Qian Xing, Wen Cui, Jieyuan Li, Sujuan Wu, Lidong Sun 2019, 40 (5):  647-655.  DOI: 10.1016/S1872-2067(19)63277-8 Abstract ( 386 )   [Full Text(HTML)] () PDF (1100KB) ( 823 )   Supporting Information Bi2MoO6, a typical Bi-based photocatalyst, has received increasing interests and been widely applied in various fields. However, the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles, such as limited photo-response and low charge separation efficiency. In this work, we developed a facile method to introduce artificial oxygen vacancy into Bi2MoO6 microspheres, which could effectively address these problems and realize highly efficient visible light photocatalysis. The experimental and theoretical methods were combined to explore the effects of oxygen vacancy on the electronic structure, photocatalytic activity and the reaction mechanism toward NO removal. The results showed that the addition of NaBH4 during catalyst preparation induced the formation of oxygen vacancy in Bi2MoO6, which plays a significant role in extending the visible light absorption of Bi2MoO6. The visible light photocatalytic activity of Bi2MoO6 with oxygen vacancy was obviously enhanced with a NO removal ratio of 43.5%, in contrast to that of 25.0% with the pristine Bi2MoO6. This can be attributed to the oxygen vacancy that creates a defect energy level in the band gap of Bi2MoO6, thus facilitating the charge separation and transfer processes. Hence, more reactive radicals were generated and participated in the photocatalytic NO oxidation reaction. The in situ FT-IR was used to dynamically monitor the photocatalytic NO oxidation process. The reaction intermediates were observed and the adsorption-reaction mechanism was proposed. It was found that the reaction mechanism was unchanged by introducing the oxygen vacancy in Bi2MoO6. This work could provide new insights into the understanding of the oxygen vacancy in photocatalysis and gas-phase photocatalytic reaction mechanism.

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In situ studies on ceria promoted cobalt oxide for CO oxidation Weiwei Huan, Jie Li, Jiahui Ji, Mingyang Xing 2019, 40 (5):  656-663.  DOI: 10.1016/S1872-2067(19)63282-1 Abstract ( 252 )   [Full Text(HTML)] () PDF (1013KB) ( 476 )   In situ studies of catalysts play valuable roles in observing phase transformation, understanding the corresponding surface chemistry and the mechanism of the reaction. In this paper, ceria promoted cobalt oxide was prepared by the calcination method and investigated for the CO oxidation. The microstructure and morphology of CeO2-Co3O4 were investigated by the Scanning Electron Microscope, High-resolution transmission electron microscopy, Raman and X-ray photoelectron spectroscopy characterization. The effect of CeO2 doping on Co3O4 for CO oxidation was characterized by in situ X-ray Diffraction (in situ XRD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). In situ XRD was carried out under H2 atmosphere to evaluate the redox property of catalysts. The results indicated that the ceria doping can enhance the reducibility of Co2+ and promote the Co3+-Co2+-Co3+ cycle, owing to the oxygen replenish property of CeO2. Furthermore, adsorbed carbonate species on the surface of CeO2-Co3O4 were investigated by in situ-DRIFTS experiment. It was turned out that carbonate species on ceria promoted cobalt oxide catalysts showed different IR peaks compared with pure cobalt oxide. The carbonate species on ceria promoted catalyst are more active, and similar to free state carbonate species with weak bonding to catalyst surface, which can effectively inhibit catalyst inactivation. This study revealed the mechanism of ceria promoting CO oxidation over cobalt oxide, which will provide theoretical support for the design of efficient CO oxidation catalysts.

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Density functional theory investigation of the enhanced adsorption mechanism and potential catalytic activity for formaldehyde degradation on Al-decorated C2N monolayer Yuetan Su, Wenlang Li, Guiying Li, Zhimin Ao, Taicheng An 2019, 40 (5):  664-672.  DOI: 10.1016/S1872-2067(18)63201-2 Abstract ( 453 )   [Full Text(HTML)] () PDF (843KB) ( 1000 )   Supporting Information Carbonyl compounds, in particular formaldehyde (HCHO), are among the most common indoor air pollutants that have been found to be toxic to humans. Thus, in this study, density functional theory (DFT) calculations are performed to study the adsorption properties of HCHO on pristine and Al-decorated C2N monolayer. The results indicate that Al-decorated C2N has a strong adsorption ability for HCHO molecules with an adsorption energy of -2.585 eV. Moreover, partial density of states (PDOS), Mulliken atomic charges, and electron density distributions are calculated to investigate the adsorption enhancement mechanism. The results show that the Al atom serves as a bridge to connect the adsorbed molecules and the C2N monolayer, thus strengthening the adsorption. Furthermore, we study the adsorption of H2O and O2 with the possible generation of hydroxyl (·OH) and superoxide (O2·-) radicals, which are active for HCHO degradation; the results show that both molecules can also be strongly adsorbed on the Al-decorated C2N surface. In particular, the dissociation of H2O provides an excellent precondition for the generation of hydroxyl radicals. Our findings suggest that Al-decorated C2N can be a promising material for the adsorption and subsequent catalytic degradation of HCHO molecules.

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Exploring a broadened operating pH range for norfloxacin removal via simulated solar-light-mediated Bi2WO6 process Meijuan Chen, Yu Huang, Wei Chu 2019, 40 (5):  673-680.  DOI: 10.1016/S1872-2067(19)63285-7 Abstract ( 154 )   [Full Text(HTML)] () PDF (459KB) ( 401 )   Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norfloxacin degradation over a narrow pH range. To broaden the operating pH range of the SSL/Bi2WO6 process, an NH4+ buffer system and an Fe3+ salt were introduced under extremely basic and acidic pH conditions, respectively. The NH4+ buffer system continuously supplied hydroxyl ions to generate·OH radicals and prevented acidification of the solution, resulting in improved norfloxacin removal and mineralization removal under alkaline conditions. In contrast, the Fe3+ salt offered an additional homogeneous photo-sensitization pathway. The former treatment assisted in norfloxacin decay and the latter increased the collision frequency between the photo-generated hole and hydroxyl ions. Moreover, the effect of parameters such as pH and Fe3+ dosage was optimized.

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Synergetic effect between non-thermal plasma and photocatalytic oxidation on the degradation of gas-phase toluene: Role of ozone Haoling Ye, Yiqiu Liu, Si Chen, Haiqiang Wang, Zhen Liu, Zhongbiao Wu 2019, 40 (5):  681-690.  DOI: 10.1016/S1872-2067(18)63185-7 Abstract ( 291 )   [Full Text(HTML)] () PDF (1145KB) ( 771 )   In this study, a hybrid process using non-thermal plasma (NTP) and photocatalytic oxidation (PCO) was adopted for the degradation of gas-phase toluene using TiO2 as the photocatalyst. To discover the synergetic effect between NTP and PCO, the performances of both sole (O3, UV, NTP, and PCO) and combined (O3 + TiO2, O3 + UV, NTP + UV, O3 + PCO, and NTP + PCO) processes were investigated from different perspectives, such as the toluene removal efficiency, selectivity of COx, mineralization rate, ozone utilization, and the generation of by-products. The toluene removal efficiency of the combined NTP + PCO process was 80.2%, which was much higher than that of a sole degradation process such as NTP (18.8%) and PCO (13.4%). The selectivity of CO2 and the ozone utilization efficiency also significantly improved. The amount of by-products in the gas phase and the carbon-based intermediates adsorbed on the catalyst surface dramatically reduced. The improvement in the overall performances of the combined NTP + PCO process was mainly ascribed to the efficient utilization of ozone in the photocatalytic oxidation, and the ozone further acting as an electron acceptor and scavenger, generating more hydroxyl radicals and reducing the recombination of electron-hole pairs.

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Light-induced ZnO/Ag/rGO bactericidal photocatalyst with synergistic effect of sustained release of silver ions and enhanced reactive oxygen species Yunyan Wu, Lili Zhang, Yazhou Zhou, Lili Zhang, Yi Li, Qinqin Liu, Juan Hu, Juan Yang 2019, 40 (5):  691-702.  DOI: 10.1016/S1872-2067(18)63193-6 Abstract ( 314 )   [Full Text(HTML)] () PDF (2083KB) ( 722 )   Supporting Information Silver nanoparticles (Ag NPs) can effectively address the issue of antibiotic-resistant bacterial infections to reduce the potential toxicity of Ag NPs. Although challenging, it is, therefore, necessary to achieve the sustainable release of Ag+ ions from a finite amount of Ag NPs. This study aims at designing an efficient and benign antimicrobial silver-based ternary composite composed of photocatalysis zinc oxide (ZnO) and reduced graphene oxide (rGO) as a carrier, in which the reactive oxygen species (ROS) excited from ZnO and Ag+ ions released from the Ag NPs cooperate to realize an effective antibacterial activity against E. coli and S. aureus. The constant effective bacterial performance of the ternary photocatalyst with minimum Ag content can be attributed to the increase in the available quantity of ROS, which results from the enhanced separation efficiency of the photogenerated carriers. The proposed system notably realized the long-term sustainable release of Ag+ ions with low concentration for 30 days when compared with an equivalent amount of silver nitrate. Moreover, the use of the composite prevents biotoxicity and silver wastage, and imparts enhanced stability to the long-lasting antibacterial efficacy.

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Exploration of the active phase of the hydrotalcite-derived cobalt catalyst for HCHO oxidation Mengya Lin, Xiaolin Yu, Xueqin Yang, Xiuyun Ma, Maofa Ge 2019, 40 (5):  703-712.  DOI: 10.1016/S1872-2067(19)63273-0 Abstract ( 166 )   [Full Text(HTML)] () PDF (1815KB) ( 468 )   A series of Co-based oxide catalysts were prepared by calcining hydrotalcite precursors in different atmospheres and studied for HCHO catalytic oxidation. The N2-calcined catalyst exhibits enhanced HCHO oxidation and superior stability. On the basis of H2-TPR, X-ray photoelectron spectroscopy, and Raman characterizations, this can be ascribed to better redox ability, octahedrally coordinated Co2+ ions derived from the CoO phase, and other surface oxygen species, such as O2- or O-. The extra octahedrally coordinated Co2+ ions may reside in a more open framework site than the inactive tetrahedrally coordinated Co2+ ions. This species of Co2+ can easily make contact with oxygen and oxidize. The surface oxygen species, along with the octahedrally coordinated Co2+ ions, and a part of the Co3+ species constitute the Co2+-oxygen species-Co3+ sites, which enhance the catalytic activities. According to DRIFTS, Co2+-oxygen species-Co3+ makes oxidation of HCHO and conversion of DOM to formate easier.

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Pt/Bi24O31Cl10 composite nanosheets with significantly enhanced photocatalytic activity under visible light irradiation Boran Xu, Juan Li, Lu Liu, Yandong Li, Shaohui Guo, Yangqin Gao, Ning Li, Lei Ge 2019, 40 (5):  713-721.  DOI: 10.1016/S1872-2067(18)63156-0 Abstract ( 352 )   [Full Text(HTML)] () PDF (781KB) ( 808 )   Efficient composite semiconductor photocatalysts are highly desirable for the visible-light-driven degradation of organic pollutants. In this study, Bi24O31Cl10 photocatalyst was prepared via a hydrothermal method and modified with Pt nanoparticles (NPs) through a facile deposition procedure. The composite photocatalyst was characterized by X-ray diffraction, transmission electronic microscopy, X-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, photoluminescence spectroscopy, and electron spin resonance. The 1.0 wt% Pt/Bi24O31Cl10 photocatalyst showed the highest activity for the degradation of methyl orange under visible light (source:300 W Xe lamp coupled with a UV-cutoff filter), and the photocatalytic degradation efficiency improved about 2.2 times compared to that of pure Bi24O31Cl10. The composite photocatalyst could maintain most of its activity after four runs of the photocatalytic experimental cycle. This study could provide a novel insight for the modification of other desirable semiconductor materials to achieve high photocatalytic activities.

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Three-dimensional ordered macroporous perovskite-type La1-xKxNiO3 catalysts with enhanced catalytic activity for soot combustion: the Effect of K-substitution Xuelei Mei, Jing Xiong, Yuechang Wei, Chujun Wang, Qiangqiang Wu, Zhen Zhao, Jian Liu 2019, 40 (5):  722-732.  DOI: 10.1016/S1872-2067(18)63269-9 Abstract ( 157 )   [Full Text(HTML)] () PDF (1706KB) ( 681 )   Three-dimensional ordered macroporous (3DOM) La1-xKxNiO3 perovskite-type catalysts were successfully prepared by a colloidal crystal template method and characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray scattering elemental mapping, X-ray diffraction, Raman and X-ray photoelectron spectroscopy, and temperature-programmed reduction of H2. Further, their catalytic activity in soot combustion was determined by temperature-programmed oxidation reaction. K substitution into the LaNiO3 lattice led to remarkably improved catalytic activity of this catalyst in soot combustion. Amongst various catalysts, La0.95K0.05NiO3 exhibited the highest activity in soot combustion (with its T50 and SCO2 values being 338℃ and 98.2%, respectively), which is comparable to the catalytic activities of Pt-based catalysts under the condition of poor contact between the soot and the catalyst. K-substitution improves the valence state of Ni and increases the number of oxygen vacancies, thereby leading to increased density of surface-active oxygen species. The active oxygen species play a vital role in catalyzing the elimination of soot. The perovskite-type La1-xKxNiO3 nanocatalysts with 3DOM structure without noble metals have potential for practical applications in the catalytic combustion of diesel soot particles.

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Doping effect of cations (Zr4+, Al3+, and Si4+) on MnOx/CeO2 nano-rod catalyst for NH3-SCR reaction at low temperature Xiaojiang Yao, Jun Cao, Li Chen, Keke Kang, Yang Chen, Mi Tian, Fumo Yang 2019, 40 (5):  733-743.  DOI: 10.1016/S1872-2067(18)63204-8 Abstract ( 138 )   [Full Text(HTML)] () PDF (1009KB) ( 544 )   Supporting Information Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano-rods (i.e., CeO2-NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano-rods were used as supports to prepare MnOx/CeO2-NR, MnOx/CZ-NR, MnOx/CA-NR, and MnOx/CS-NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, Raman and N2-physisorption analyses, hydrogen temperature-programmed reduction, ammonia temperature-programmed desorption, in situ diffuse reflectance infrared Fourier-transform spectroscopic analysis of the NH3 adsorption, and X-ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3-selective catalytic reduction (NH3-SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS-NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS-NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2-NR catalyst.

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Improved visible light photocatalytic activity of mesoporous FeVO4 nanorods synthesized using a reactable ionic liquid Hanxiang Chen, Jie Zeng, Mindong Chen, Zhigang Chen, Mengxia Ji, Junze Zhao, Jiexiang Xia, Huaming Li 2019, 40 (5):  744-754.  DOI: 10.1016/S1872-2067(19)63272-9 Abstract ( 133 )   [Full Text(HTML)] () PDF (722KB) ( 405 )   Supporting Information Mesoporous FeVO4 nanorods were successfully synthesized by calcining the precursor FeVO4·1.1H2O nanorods, which were obtained via a simple hydrothermal method in the presence of a reactable metal-ion-containing ionic liquid, 1-octyl-3-methylimidazolium tetrachloride ferrate(Ⅲ) ([Omim]FeCl4). The structure and morphology of the prepared samples were examined using various characterization techniques. During the synthetic process,[Omim]FeCl4 acted as the solvent, reactant, and capping agent simultaneously. Moreover, the porous FeVO4 nanorods as the heterogeneous photo-Fenton-like semiconductor catalyst for the degradation of tetracycline and rhodamine B under visible light irradiation exhibited excellent photocatalytic activity. This excellent photocatalytic activity of the porous FeVO4 nanorods can be attributed to the synergistic effect of their high electron-hole pair separation rate, suitable band gap structure, and large specific surface area. The possible photocatalytic degradation mechanism of FeVO4/H2O2 photocatalytic systems was also discussed in detail.

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SPR effect of bismuth enhanced visible photoreactivity of Bi2WO6 for NO abatement Li Zhang, Chao Yang, Kangle Lv, Yachao Lu, Qin Li, Xiaofeng Wu, Yuhan Li, Xiaofang Li, Jiajie Fan, Mei Li 2019, 40 (5):  755-764.  DOI: 10.1016/S1872-2067(19)63320-6 Abstract ( 350 )   [Full Text(HTML)] () PDF (977KB) ( 798 )   Bi2WO6 is a typical visible-light-responsive semiconductor photocatalyst with a layered structure. However, the relatively large bandgap (2.6-2.8 eV) and quick recombination of photo-generated carriers result in its low quantum efficiency. In this paper, Bi-nanospheres-modified flower-like Bi2WO6 was successfully prepared by solvothermal treatment of Bi2WO6 powders in Bi(NO3)3 solution using ethylene glycol as reductant. The photoreactivity of this photocatalyst was evaluated by the oxidation of NO in a continuous-flow reactor under irradiation by a visible LED lamp (λ > 400 nm). It was found that both Bi nanospheres and flower-like Bi2WO6 precursor exhibit very poor photocatalytic activity with NO removal rates of only 7.7% and 8.6%, respectively. The photoreactivity of Bi/Bi2WO6 was found to steadily increase from 12.3% to 53.1% with increase in the amount of Bi nanospheres from 0 to 10 wt%. However, with further increase in the loading amount of Bi nanospheres, the photoreactivity of Bi/Bi2WO6 hybridized photocatalyst begins to decrease, possibly due to the light filtering by the Bi nanospheres. The enhanced visible photoreactivity of Bi/Bi2WO6 towards NO abatement was attributed to surface plasmon resonance driven interfacial charge separation. The excellent stability of Bi/Bi2WO6 hybridized photocatalyst towards NO oxidation demonstrates its potential for applications such as air purification.

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Simultaneous formation of a C/N-TiO2 hollow photocatalyst with efficient photocatalytic performance and recyclability Yingguan Xiao, Xiaodong Sun, linyu Li, Juanrong Chen, Shidong Zhao, Caiguo Jiang, Luyao Yang, Li Cheng, Shunsheng Cao 2019, 40 (5):  765-775.  DOI: 10.1016/S1872-2067(19)63286-9 Abstract ( 151 )   [Full Text(HTML)] () PDF (1060KB) ( 436 )   Herein, we report a unique approach towards the preparation of C-modified and N-doped TiO2 hollow spheres (C/N-TiO2). TEM, SEM, and XPS analyses were used to confirm that the carbon and nitrogen co-decorated TiO2 photocatalyst was formed. Carbon-decoration improves the visible-light absorption and speeds up the separation of the photo-generated electron-hole pairs. C/N-TiO2 not only narrows the band gap of TiO2, but also exhibits excellent photocatalytic activity for the degradation of tetracycline and tetracycline hydrochloride. In addition, the C/N-TiO2 photocatalyst shows excellent recyclability for water decontamination, making it a promising candidate to purify aquatic contaminants.

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Unique electronic structure of Mg/O co-decorated amorphous carbon nitride enhances the photocatalytic tetracycline hydrochloride degradation Xiaolu Wu, Min Fu, Peng Lu, Qiuyan Ren, Cheng Wang 2019, 40 (5):  776-785.  DOI: 10.1016/S1872-2067(19)63300-0 Abstract ( 107 )   [Full Text(HTML)] () PDF (842KB) ( 559 )   g-C3N4 is a hot visible light photocatalyst. However, the fast recombination of photogenerated electron-hole pairs leads to unsatisfactory photocatalytic efficiencies. In this study, Mg/O co-decorated amorphous carbon nitride (labeled as MgO-CN) with a unique electronic structure was designed and prepared via a combined experimental and theoretical approach. The results showed that the MgO-CN exhibited an increased light absorption ability and promoted charge separation efficiency. The Mg and O co-decoration created a unique structure that could generate localized electrons around O atoms and enhance the reactant activation capacities via the C→O←Mg route. This could dramatically promote the O2 molecule activation on the catalyst surface to generate reactive species (·O2-/·OH). The optimized MgO-CN exhibited a high photocatalytic activity for the degradation of tetracycline hydrochloride in water, which was five times higher than that of pristine g-C3N4. The present work could provide a new strategy for modifying the electronic structure of g-C3N4 and enhancing its performance for environmental applications.

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Preparation of amphiphilic TiO2 Janus particles with highly enhanced photocatalytic activity Yanting Shi, Qiaoling Zhang, Youzhi Liu, Junbo Chang, Jing Guo 2019, 40 (5):  786-794.  DOI: 10.1016/S1872-2067(19)63332-2 Abstract ( 177 )   [Full Text(HTML)] () PDF (1313KB) ( 452 )   Stearic-acid-modified TiO2 (STA-TiO2) particles were prepared via the impregnation approach and used as a precursor for preparing TiO2 Janus particles. The morphology, structure, and properties of the TiO2 Janus particles were characterized using Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, thermogravimetric analysis, fluorescence microscopy, high-resolution transmission electron microscopy, contact angle analysis, dynamic light scattering, biological microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy measurements. The results show that TiO2 Janus particles can be successfully prepared via toposelective surface modification. STA grafted on the surface of TiO2 enhances its hydrophobicity, promotes charge separation, and improves its adsorption capacity for organic compounds. The TiO2 Janus particles strongly adsorb on an oil-water interface to form a stable Pickering emulsion. The degradation rates of high-concentration kerosene and nitrobenzene wastewaters when the photocatalyst is pure TiO2, STA-TiO2, or TiO2 Janus particles are discussed and compared. The degradation rates were determined using an ultraviolet-visible spectrophotometer. It was found that the Pickering emulsion stabilized by the TiO2 Janus particles exhibited the best photocatalytic performance; these Janus particles show promising potential for catalytic application.