Solvent-driven morphology-controlled synthesis of highly efficient long-life ZnO/graphene nanocomposite photocatalysts for the practical degradation of organic wastewater under solar light

Nguyen, Van Quang,Baynosa, Marjorie Lara,Nguyen, Van Hoa,Tuma, Dirk,Lee, Yong Rok,Shim, Jae-Jin Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.486 No.-

<P><B>Abstract</B></P> <P>Metal oxide/graphene photocatalysts have been attracting considerable attention in solving environmental pollution problems because of the limitations of the semiconductor-based photocatalysts. In this study, highly efficient and inexpensive zinc oxide (ZnO) nanoparticles with three different morphologies, such as nanospheres, nanodisks, and nanorods, anchored on reduced graphene oxide (RGO) were synthesized in solvent mixtures with different ethanol to water ratios. Among the three morphologies, the nanospherical ZnO/RGO (sZG) composite exhibited the highest methylene blue (MB) and rhodamine B removal efficiencies at 99% and 98%, respectively, after only 60 min under low-power (40 W) ultraviolet irradiation at a low catalyst loading of 0.1 g L<SUP>−1</SUP>. This nanocomposite also showed excellent photocatalytic stability under UV irradiation, retaining 96% efficiency even after 15 cycles of MB degradation. Moreover, the sZG composite exhibited a high MB degradation efficiency of approximately 99% after 100 min at a low catalyst loading of 0.2 g L<SUP>−1</SUP> under solar light illumination. The excellent photocatalytic performance and high stability of this low-cost nanospherical ZnO/RGO composite exemplarily highlights the potential of sustainable next-generation photocatalysis for treating wastewater containing organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Size/morphology of ZnO particles were controlled by the water-ethanol solvent ratio </LI> <LI> The critical roles of ZnO seed and HMTA in forming the particles were investigated. </LI> <LI> Catalytic performance was controlled by the morphology of ZnO nanoparticles and RGO </LI> <LI> Nanospherical ZnO/RGO showed an excellent MB photodegradation efficiency of 99%. </LI> <LI> Nanospherical ZnO/RGO exhibited a remarkable stability (96% after 15 cycles). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Heterogeneous activation of peroxymonosulfate by a novel magnetic 3D γ-MnO₂@ZnFe₂O₄/rGO nanohybrid as a robust catalyst for phenol degradation

Mady, Amr Hussein,Baynosa, Marjorie Lara,Tuma, Dirk,Shim, Jae-Jin Elsevier 2019 Applied Catalysis B Vol.244 No.-

<P><B>Abstract</B></P> <P>Three-dimensional (3D) γ-MnO<SUB>2</SUB>@ZnFe<SUB>2</SUB>O<SUB>4</SUB>/reduced graphene oxide (rGO) nanohybrids were synthesized using a one-pot hydrothermal self-assembly method. The morphology and properties of the nanohybrids were investigated. The synergistic interactions among γ-MnO<SUB>2</SUB>, ZnFe<SUB>2</SUB>O<SUB>4</SUB>, and rGO resulted in 3D nanoflakes distributed uniformly in the rGO structure with a thickness of approximately 2–5 nm, leading to a high surface area. The nanohybrid containing 10 wt. % rGO exhibited superior catalytic activities for phenol degradation through the activation of peroxymonosulfate (PMS) to generate active sulfate radicals ( S O 4 • – ). Typically, 50 mL of a 20 ppm phenol solution was degraded completely and 85% of the carbon content had been mineralized in 30 min at 25 °C using 10 mg of the nanohybrid. The nanohybrid could be recovered easily using a magnet and reused, maintaining high stability during catalytic oxidation. The 3D γ-MnO<SUB>2</SUB>@ZnFe<SUB>2</SUB>O<SUB>4</SUB>/rGO nanohybrid catalyst could be applied to the removal of hard-to-degrade waste materials owing to its high efficiency and excellent reusability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3D γ-MnO<SUB>2</SUB>@ZnFe<SUB>2</SUB>O<SUB>4</SUB>/rGO nanohybrid was synthesized by one-pot hydrothermal method. </LI> <LI> The hybrid had a very large surface area and showed very high performance. </LI> <LI> The hybrid decomposed 20 ppm phenol in 30 min in the presence of PMS. </LI> <LI> 95% of the carbon content was mineralized in 3 h. </LI> <LI> The hybrid showed excellent recyclability and reusability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facile microwave-assisted green synthesis of Ag-ZnFe₂O₄@rGO nanocomposites for efficient removal of organic dyes under UV- and visible-light irradiation

Mady, Amr Hussein,Baynosa, Marjorie Lara,Tuma, Dirk,Shim, Jae-Jin Elsevier BV 2017 Applied Catalysis B Vol.203 No.-

<P><B>Abstract</B></P> <P>Nanocomposites of Ag-ZnFe<SUB>2</SUB>O<SUB>4</SUB>@reduced graphene oxide (rGO) were synthesized using a one-pot microwave-assisted self-assembly method. The morphology and structure of the Ag-ZnFe<SUB>2</SUB>O<SUB>4</SUB>@rGO nanocomposites were characterized. The nanocomposites formed with 15.2wt% rGO showed excellent adsorption properties and high photocatalytic activity for the degradation of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO). The synergistic interactions between Ag, ZnFe<SUB>2</SUB>O<SUB>4</SUB>, and rGO decreased the aggregation of the nanoparticles (NPs) and increased the surface area, resulting in better absorption in both UV and visible light. Such a structure was helpful for separating the photo-excited electron-hole pairs and accelerating electron transfer. Electrochemical impedance spectroscopy (EIS) revealed a smaller resistance in the solid-state interface layer and charge transfer on the composite surface than that of the bare ZnFe<SUB>2</SUB>O<SUB>4</SUB> NPs and ZnFe<SUB>2</SUB>O<SUB>4</SUB>@rGO nanocomposite. The Ag-ZnFe<SUB>2</SUB>O<SUB>4</SUB>@rGO nanocomposite could be recovered easily by a magnet and reused five times with no significant decrease in photocatalytic activity. The as-prepared Ag-ZnFe<SUB>2</SUB>O<SUB>4</SUB>@rGO nanocomposite catalyst could be applied to the removal of hard-to-degrade waste materials owing to its high efficiency in both UV and visible light and its excellent reusability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag-ZnFe<SUB>2</SUB>O<SUB>4</SUB>@rGO composite was synthesized by one-pot microwave method in 10min. </LI> <LI> The composite had a very large surface area and showed very high performance. </LI> <LI> The composite decomposed 20ppm MB very fast within 30min under visible light only. </LI> <LI> The composite showed excellent recyclability and reusability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hierarchical mesoporous carbon sphereνickel cobalt sulfide core-shell structures and their electrochemical performance

Lamiel, C.,Nguyen, V.H.,Baynosa, M.,Huynh, D.C.,Shim, J.J. Elsevier Sequoia 2016 Journal of Electroanalytical Chemistry Vol.771 No.-

<P>The pursuit for renewable sources of energy has increased rapidly due to the continuous depletion of nonrenewable sources. Supercapacitors have attracted considerable attention because they can store electrical energy. In this study, a hierarchical mesoporous carbon sphere@nickel cobalt sulfide (CS@Ni-Co-S) core-shell was synthesized using a facile hydrothermal method. The reaction involved green synthesis without further sulfurization or post-heat treatment. The CS@Ni-Co-S core-shell microstructures exhibited a high capacitance of 724.4 F g(-1) at 2 A g(-1) in a 6 M KOH electrolyte. Good specific retention of 86.1% and high Coulombic efficiency of 97.9% were obtained after 2000 charge-discharge cycles. High energy density (58.0 Wh kg(-1) at 1440 W kg(-1)) and high power density (34.2 Wh kg(-1) at 7200W kg(-1)) were observed. Through this study, a cost-effective and simple synthesis of CS@Ni-Co-S as an active electrode showed favorable electrochemical performance. (C) 2016 Elsevier B.V. All rights reserved.</P>

Potentiodynamic formation of diaminobenzene films on an electrochemically reduced graphene oxide surface: Determination of nitrite in water samples

Kesavan, Srinivasan,Kumar, Deivasigamani Ranjith,Baynosa, Marjorie Lara,Shim, Jae-Jin Elsevier 2018 Materials science & engineering. C, Materials for Vol.85 No.-

<P><B>Abstract</B></P> <P>An electrode comprised of a polydiaminobenzene (p-DAB) film formed on electrochemically reduced graphene oxide (ERGO) on a glassy carbon (GC) (p-DAB@ERGO/GC) was fabricated using a potentiodynamic method for the sensitive and selective determination of nitrite in the presence of a common interference. The p-DAB@ERGO/GC film-modified electrode surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The film fabrication was initiated via the NH<SUB>2</SUB> groups of DAB, which was confirmed by XPS from the peaks corresponding to NH (396.7eV), NH (399.4eV), NN (400.2eV), and N<SUP>+</SUP>H (402.2eV). The Raman spectra revealed the characteristic D and G bands at 1348 and 1595cm<SUP>−1</SUP>, respectively, which confirmed the fabrication of GO on the GC electrode, and the ratio of the D and G bands was increased after the electrochemical reduction of GO. The surface coverage of the modified electrode was 8.16×10<SUP>−11</SUP> molcm<SUP>−2</SUP>. The p-DAB@ERGO/GC film-modified electrode was used successfully for the determination of nitrite ions. The p-DAB@ERGO/GC film-modified electrode exhibited superior activity for the determination of nitrite compared to the bare GC and p-DAB@GC electrodes. The amperometric current increased linearly with increasing nitrite concentration from 7.0×10<SUP>−6</SUP> to 2.0×10<SUP>−2</SUP> M. The detection limit was 30nM (S/N=3). In addition, the modified electrode was used successfully to determine the nitrite ion concentration in the presence of a 100-fold excess of common interferents. The practical application of the modified electrode was demonstrated by determining the nitrite ion concentration in water samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel diaminobenzene film on ERGO was fabricated by potentiodynamic method. </LI> <LI> p-DAB@ERGO/GC shows excellent activity towards nitrite. </LI> <LI> The proposed sensor exhibits lowest detection limit and wide linear range. </LI> <LI> Modified electrode was successfully applied to the analysis in water samples. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Flower-like Cu_1.8S nanostructures for high-performance flexible solid-state supercapacitors

Ranjith Kumar, Deivasigamani,Kesavan, Srinivasan,Baynosa, Marjorie Lara,Shim, Jae-Jin Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.448 No.-

<P><B>Abstract</B></P> <P>In wearable and portable electronic devices, small size, light weight, flexibility, and easy operability are necessary for energy storage systems, such as battery and supercapacitor. To improve the performance, high specific capacity and high energy and power densities are also required. In this study, flower-like Cu<SUB>1.8</SUB>S nanostructures are synthesized from a single source tris(thiourea)copper(I) chloride complex precursor. The different-sized Cu<SUB>1.8</SUB>S nanostructures with flower-like petal morphology are successfully synthesized by addition of capping agents such as sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid (EDTA) with ethylene glycol (EG) as a solvent. The petal thicknesses vary from 60 to 30 nm, resulting in the increase in its specific surface area. The as-prepared nanostructures are tested for their supercapacitor performances in KOH electrolyte medium. The EDTA-Cu<SUB>1.8</SUB>S electrode provides a high specific capacitance of 1050.0 F g<SUP>−1</SUP> as compared with SDS-Cu<SUB>1.8</SUB>S (773.0 F g<SUP>−1</SUP>) and EG-Cu<SUB>1.8</SUB>S (625.4 F g<SUP>−1</SUP>). Flexible solid-state symmetric supercapacitors are also fabricated from EDTA-Cu<SUB>1.8</SUB>S which deliver a high volumetric capacitance (4.5 F cm<SUP>−3</SUP>) and energy density (0.5 mWh cm<SUP>−3</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flower-like Cu<SUB>1.8</SUB>S was synthesized from tris(thiourea)copper(I)chloride complex. </LI> <LI> Flower-like Cu<SUB>1.8</SUB>S with different petal morphology was prepared. </LI> <LI> A flexible SSC decorated with 3D flower-like Cu<SUB>1.8</SUB>S was prepared. </LI> <LI> Flower-like Cu<SUB>1.8</SUB>S SSC with thinner petal thickness showed high capacitance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Flower-like Bi₂S₃ nanostructures grown on nitrogen-doped reduced graphene oxide for electrochemical determination of hydrogen peroxide

Kumar, Deivasigamani Ranjith,Kesavan, Srinivasan,Baynosa, Marjorie Lara,Nguyen, Van Quang,Shim, Jae-Jin Elsevier 2018 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.530 No.-

<P><B>Abstract</B></P> <P>This paper reports a facile solvothermal method for the synthesis of Bi<SUB>2</SUB>S<SUB>3</SUB> flower-like nanostructures grown <I>in situ</I> on a nitrogen-doped reduced graphene oxide (Bi<SUB>2</SUB>S<SUB>3</SUB>@N-G) surface. Thiourea was used as the nitrogen source and reducing agent for graphene oxide. The surface morphology of the as-prepared Bi<SUB>2</SUB>S<SUB>3</SUB>@N-G composites was analyzed by field emission scanning electron microscopy and transmission electron microscopy. The crystalline structure and surface chemical states were examined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The as-prepared Bi<SUB>2</SUB>S<SUB>3</SUB>@N-G composite was deposited on a glassy carbon (GC) electrode, and the modified electrode was employed for the electrocatalytic detection of H<SUB>2</SUB>O<SUB>2</SUB>. The calculated diffusion coefficient and catalytic rate constant of the Bi<SUB>2</SUB>S<SUB>3</SUB>@N-G modified electrode were 4.9 × 10<SUP>−6</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP> and 5671 M<SUP>−1</SUP> s<SUP>−1</SUP>, respectively. The Bi<SUB>2</SUB>S<SUB>3</SUB>@N-G/GC electrode demonstrated a wide concentration range for H<SUB>2</SUB>O<SUB>2</SUB>, from 10 to 42,960 μM, with a sensitivity of 0.1535 μA μM<SUP>−1</SUP> and an obtained limit of detection of 1.9 μM.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

3,5-Diamino-1,2,4-triazole@electrochemically reduced graphene oxide film modified electrode for the electrochemical determination of 4-nitrophenol

Kumar, Deivasigamani Ranjith,Kesavan, Srinivasan,Baynosa, Marjorie Lara,Shim, Jae-Jin Elsevier 2017 ELECTROCHIMICA ACTA Vol.246 No.-

<P><B>Abstract</B></P> <P>In this study, an eco-friendly benign method for the modification of electrochemically reduced graphene oxide (ERGO) on glassy carbon (GC) surface and electrochemical polymerized 3,5-diamino-1,2,4-triazole (DAT) film composite (pDAT@ERGO/GC) electrode was developed. The surface morphologies of the pDAT@ERGO/GC modified electrode were analyzed by field emission scanning electron microscopy (FESEM). FESEM images indicated that the ERGO supported pDAT has an almost homogeneous morphology structure with a size of 70 to 80nm. It is due to the water oxidation reaction occurred while pDAT@ERGO/GC fabrication peak at +1.4V leads to O<SUB>2</SUB> evolution and oxygen functional group functionalization on ERGO, which confirmed by X-ray photoelectron spectroscopy (XPS). In contrast, the bare GC modified with pDAT showed randomly arranged irregular bulky morphology structure compared to those of pDAT@ERGO/GC. Electrochemical reduction of graphene oxide was confirmed by Raman spectroscopy, XPS, and electrochemical impedance spectroscopy (EIS). The pDAT@ERGO/GC modified electrode was used for the electrochemical determination of 4-nitrophenol (4-NP). The 4-NP oxidation peak was observed at +0.25V, and the differential pulse voltammetry demonstrated wide concentration range (5–1500μM), high sensitivity (0.7113μA μM<SUP>−1</SUP>), and low limit of detection (37nM). Moreover, the pDAT@ERGO/GC electrode was applied to real water sample analysis by standard addition method, where in good recoveries (97.8% to 102.4%) were obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Triazole film was formed on electrochemically reduced graphene oxide. </LI> <LI> pDAT@ERGO/GC was utilized for the electrochemical determination of 4-nitrophenol. </LI> <LI> pDAT@ERGO/GC electrode offered wide concentration and nanomolar detection limit. </LI> <LI> The fabricated electrode was employed in water sample analyses. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Solar light-active S-scheme TiO2/In2S3 heterojunction photocatalyst for organic pollutants degradation

Manjiri A. Mahadadalkar,Ganesh Dhakal,Sumanta Sahoo,Deivasigamani Ranjith Kumar,Marjorie Lara Baynosa,Van Quang Nguyen,Mostafa Saad Sayed,Abdelrahman M. Rabie,Woo Kyoung Kim,Jae-Jin Shim 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.124 No.-

Heterojunction TiO2/In2S3 composite photocatalyst was prepared using a simple low-temperature onestephydrothermal method. In2S3 nanosheets with a thickness of 1–5 nm were decorated with 20–30 nm TiO2 nanoparticles, forming a stable heterojunction. The electron transfer mechanism and bandalignment between TiO2 and In2S3 was studied using X-ray photoelectron spectroscopy and UV–visiblespectroscopy, which suggested the formation of an S-scheme heterojunction in TiO2/In2S3 composite. The TiO2/In2S3 composite with a 1:1 mole ratio showed 99.9% photocatalytic degradation ofRhodamine B within 20 minutes of solar light irradiation, which was better than the results for pristineTiO2, pristine In2S3, and their physical mixture, as well as any other previously reported materials of thesame kind. The as-prepared TiO2/In2S3 composite showed excellent stability (98% for Rhodamine B) evenafter five successive reuse cycles. This excellent performance of TiO2/In2S3 was attributed to the S-schemeheterojunction because of an internal electric field, columbic attraction, and band bending. A radical trappingstudy showed that superoxide radicals O2 contribute the most to the photocatalytic degradationof Rhodamine B followed by hydroxyl radicals (OH) and holes (hVB+ ). The use of a low synthesis temperatureand a simple, one-step formation method, with no secondary pollutants generated, makes this processan environmentally friendly and sustainable solution for cost-effective wastewater treatment,highlighting its future commercial applications.