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High-Efficiency Photocatalytic Degradation of Tannic Acid Using TiO₂ Heterojunction Catalysts.

ABSTRACT: Photocatalysts have been extensively used for hydrogen evolution or organic degradation. In this work, two different heterojunction types of composite photocatalysts, 1T-MoS₂@TiO₂ with Schottky heterojunction and 2H-MoS₂@TiO₂ with type-II heterojunction, are synthesized via hydrothermal synthesis. These two composite materials exhibit excellent photocatalytic activity toward the degradation of tannic acid, which is a typical organic in nuclear wastewater. At an optimal loading of 16% 1T-MoS₂, the 1T-MoS₂@TiO₂ shows the highest degradation capacity of 98%, which is 3.2 times higher than that of pure TiO₂. The degradation rate of 16% 1T-MoS₂@TiO₂ is much higher than that of 13% 2H-MoS₂@TiO₂. The enhanced photocatalytic activity might be attributed to the improved charge transfer according to the mechanism investigation, supported by the X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) analyses. This work provides new opportunities for constructing highly efficient catalysts for nuclear waste disposal.

SUBMITTER: Liu R

PROVIDER: S-EPMC8567273 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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High-Efficiency Photocatalytic Degradation of Tannic Acid Using TiO2 Heterojunction Catalysts.

Liu Ruixi R Wu Linzhen L Liu Hao H Zhang Youkui Y Ma Jianjun J Jiang Cairong C Duan Tao T

ACS omega 20211022 43

Photocatalysts have been extensively used for hydrogen evolution or organic degradation. In this work, two different heterojunction types of composite photocatalysts, 1T-MoS2@TiO2 with Schottky heterojunction and 2H-MoS2@TiO2 with type-II heterojunction, are synthesized via hydrothermal synthesis. These two composite materials exhibit excellent photocatalytic activity toward the degradation of tannic acid, which is a typical organic in nuclear wastewat ...[more]

PMID: 34746549

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Project description:In this study, a variety of ZnO-based heterojunctions with disparate wt.% doping of WO3 and BiOI have been prepared for the photodestruction of methyl orange (MO) dye in aqueous solution. The composites were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, optical studies, and nitrogen adsorption-desorption isotherms. The SEM images revealed non-uniform surfaces of the ZnO-BiOI based composites while mostly nodular morphology was observed for all three samples of ZnO-WO3. As the WO3 loading increased, more clustering was detected. The analysed samples exhibited characteristic peaks representative of the triclinic phase of WO3 and the hexagonal wurtzite structure of ZnO, while the diffractogram observed from the materials displayed distinct peaks corresponding to the crystalline phases of both BiOI and ZnO in their pure forms. Further evidence of the samples' characteristics includes the presence of distinct crystalline patterns without any impurity peaks, a red shift in the absorption spectra of the heterostructure, the detection of only the reference elements, and mostly Type IV isotherm adsorption. This study identified the ZnO-[10%]BiOI and ZnO-[10%]WO3 heterojunctions as the best performing photocatalysts, as MO was completely destroyed in 120 and 90 min, respectively. Thus, confirming 10% wt. as the optimal doping concentration for the best photo-activity in this study. The impact of varying process parameters demonstrates that at an elevated photocatalyst mass of 40 mg, both heterojunctions effectively degraded MO. The photodegradation efficiency of MO was more pronounced in strong acidic conditions (pH 2) when compared to high alkaline conditions (pH 11) for the ZnO-[10%]BiOI heterostructure. However, a decrease in performance was observed for both strong acidic and high alkaline pH values when the ZnO-[10%]WO3 heterostructure was applied. The kinetic analysis of the photodegradation study reveals that all the photodegradation experiments can be represented by the pseudo-first-order kinetic model. The findings from this investigation propose that the ZnO-[10%]BiOI heterojunction photocatalyst holds significant potential for the effective treatment of dye-contaminated wastewater.

Project description:Perfluorooctanoic acid (PFOA), a typical perfluorinated carboxylic acid, is an emerging type of permanent organic pollutants that are regulated by the Stockholm Convention. The degradation of PFOA, however, is quite challenging largely due to the ultra-high stability of C-F bonds. Compared with other techniques, photocatalytic degradation offers the potential advantages of simple operation under mild conditions as well as exceptional decomposition and defluorination efficiency. Titanium dioxide (TiO2) is one of the most frequently used photocatalysts, but so far, the pristine nanosized TiO2 (e.g., the commercial P25) has been considered inefficient for PFOA degradation, since the photo-generated hydroxyl radicals from TiO2 are not able to directly attack C-F bonds. Mesoporous Sb2O3/TiO2 heterojunctions were therefore rationally designed in this work, of which the confined Sb2O3 nanoparticles in mesoporous TiO2 framework could not only tune the band structure and also increase the number of active sites for PFOA degradation. It was found that, after loading Sb2O3, the absorption of UV light was enhanced, indicating a higher efficiency of light utilization; while the band gap was reduced, which accelerated the separation of photo-generated charge carriers; and most importantly, the valence band edge of the Sb2O3/TiO2 heterojunction was significantly lifted so as to prevent the occurrence of hydroxyl radical pathway. Under the optimal ratio of Sb2O3-TiO2, the resulting catalysts managed to remove 81.7% PFOA in 2 h, with a degradation kinetics 4.2 times faster than the commercial P25. Scavenger tests and electron spin resonance spectra further revealed that such improvement was mainly attributed to the formation of superoxide radicals and photo-generated holes, in which the former drove the decarboxylation from C7F15COOH-C7F15 •, and the latter promoted the direct electron transfer for the conversion of C7F15COO--C7F15COO•. The Sb2O3/TiO2 photocatalysts were highly recyclable, with nearly 90% of the initial activity being retained after five consecutive cycles, guaranteeing the feasibility of long-term operation.

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High-Efficiency Photocatalytic Degradation of Tannic Acid Using TiO₂ Heterojunction Catalysts.

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High-Efficiency Photocatalytic Degradation of Tannic Acid Using TiO<sub>2</sub> Heterojunction Catalysts.

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