Copper oxide–graphene oxide nanocomposite: efficient catalyst for hydrogenation of nitroaromatics in water

SHOKOUHIMEHRMOHAMMADREZA,Rajender S. Varma,장호원,Ji-Won Choi,Joo Hwan Cha,Tae Hyung Lee,Jun Min Suh,Kaiqiang Zhang 나노기술연구협의회 2019 Nano Convergence Vol.6 No.6

A low-cost nanocomposite catalyst containing copper oxide (CuO) nanoparticles (NPs) on graphene oxide (GO) was fabricated by a facile hydrothermal self-assembly process. The segregated CuO NPs and GO exhibited negligible catalytic activities for the reduction of nitroaromatics. However, their hybrid composite accomplished facile reduction with high conversions for several substituted nitroaromatics in aqueous NaBH4 solution; synergetic coupling effect of CuO NPs with GO in the nanocomposite catalyst provided excellent catalytic activity. The nanocomposite catalyst could be separated from the reaction mixture and recycled consecutively.

+Iron hexacyanocobaltate metal-organic framework: Highly reversible and stationary electrode material with rich borders for lithium-ion batteries

Zhang, Kaiqiang,Varma, Rajender S.,Jang, Ho Won,Choi, Ji-Won,Shokouhimehr, Mohammadreza Elsevier 2019 Journal of Alloys and Compounds Vol.791 No.-

<P><B>Abstract</B></P> <P>Metal-organic frameworks (MOFs) are attractive electrode material candidates for lithium-ion batteries (LIBs) and are garnering significant interest due to their tunable pore size and intriguing electrochemical properties. A border-rich iron (Fe<SUP>3+</SUP>) hexacyanocobaltate (FeHCCo) MOF is synthesized via a facile and low-cost co-precipitation method and evaluated as a cathode material for LIBs. The MOF delivered reversible capacities corresponding to 136 and 57 mAh g<SUP>−1</SUP> at 0.63 and 6.25C, respectively. Furthermore, a lithiation capacity of 116 mAh g<SUP>−1</SUP> at 1.25C was maintained with a Coulombic efficiency of 99.6%. The high electrochemical performance can be attributed to the highly reversible open-framework crystal texture of border-rich FeHCCo, which may provide new insights on the application of MOFs as viable electrode materials in rechargeable LIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Iron hexacyanocobaltate exhibits an improved rate-performance of 42%. </LI> <LI> Iron hexacyanocobaltate displays a coulombic efficiency of ∼99.6%. </LI> <LI> Iron hexacyanocobaltate shows isotropic and negligible lattice strain during Li<SUP>+</SUP> ion intercalation/extraction process. </LI> <LI> Border-rich feature plays a key role in the formation of solid electrolyte interface. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced photo-Fenton assisted photocatalytic degradation of atenolol using a novel rGO embedded double Z-scheme nano-heterojunction: Mechanism, kinetics and toxicity studies

M. Raaja Rajeshwari,Asad Syed,Ali H. Bahkali,Abdallah M. Elgorban,M. Kalil Rahiman,Rajender S. Varma,S. Sudheer Khan 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

In this work, rGO-based ternary dual Z-scheme heterojunction (rGO/CuFe2O4/CdS/Bi2S3 QDs) was formulatedfor the effective photo-Fenton assisted photocatalytic degradation of a b-blocker, atenolol. The catalystwas synthesised via a simple co-precipitation/hydrothermal method and was characterized usingXRD, XPS, FT-IR, SEM, TEM, PL, EIS, ESR, Raman and DRS. It exhibited about 76.5% degradation of atenololin 360 min under visible light irradiation with a rate constant of 0.004 min1 wherein the mechanism ofenhanced activity was attributed to the formation of OH, h+ and photo-Fenton reaction; a possible mechanismwas drafted. The intermediates were determined using GC–MS analysis delineating a plausibledegradation pathway, the mineralization of atenolol being confirmed by TOC analysis. The catalyst wasreusable and highly stable up to six cycles of degradation, as affirmed via XRD and XPS analysis. Further, the toxicity of the catalyst has been studied using the root cells of Allium cepa, and the degradedproduct and intermediates were assessed deploying ECOSAR software. Thus, the proposed work haspotential which can be implemented in future for the large-scale purification of wastewater.

Fabrication of ternary nano-heterojunction via hierarchical deposition of a-Fe2O3 and b-La2S3 on cubic CoCr2O4 for enhanced photodegradation of doxycycline

P.R. Sivaranjani,Asad Syed,Abdallah M. Elgorban,Ali H. Bahkali,R. Balakrishnaraja,Rajender S. Varma,S. Sudheer Khan 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.118 No.-

The current study offers the design of a novel photocatalyst for the effective removal of pharmaceuticalswherein the heterojunction was constructed with the objective of capturing maximum solar spectrumand to ensure effective separation of photogenerated charge carriers. The nano-heterojunction was fabricatedthrough ultrasonication-assisted co-precipitation method by the hierarchical deposition of a-Fe2O3 and b-La2S3 on cubic CoCr2O4 spinel. The fabricated nanomaterials were extensively characterizedby using XRD, Raman, FTIR, XPS, SEM, TEM, EDAX, PL, EIS, BET, and DRS. The photoluminescence and EISanalysis revealed the mitigated charge carrier recombination in CoCr2O4/a-Fe2O3/b-La2S3 (CFL) thatresulted in superior photodegradation of doxycycline (DOX) (92.83 %) under visible light irradiation. Mineralization percentage of 92.5 % was affirmed by TOC analysis. Further, the influence of pH, ions, concentrationof DOX and CFL dosage on the photodegradation process was studied. The active participationof the reactive species involved in the reaction were identified by scavenging assay and ESR. Finally, apossible photocatalytic mechanism of CFL for the degradation of DOX with underlying pathway is proposedwith the help of GC–MS/MS analysis. The study highlights the great promise of CFL photocatalystas well as the potential of n-n-p heterojunction for appliances in the photodegradation of organicpollutants.

MOF-derived NiFe2O4 nanoparticles on molybdenum disulfide: Magnetically reusable nanocatalyst for the reduction of nitroaromatics in aqueous media

Jinghan Wang,김재현,Jeewon Bu,Dokyoon Kim,Soo Young Kim,남기태,Rajender S. Varma,Rajender S. Varma,Ho Won Jang,Rafael Luque,쇼코히메르모하메드레자 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.107 No.-

Metal organic framework (MOF)-derived nanocatalysts on various nanostructured supports are generallyefficient heterogeneous catalysts employable for organic transformations. Herein, nickel Prussian blue(PB) nanoparticles were deployed to form NiFe2O4 nanocatalysts supported on 2D molybdenum disulfide(MoS2) through a facile heat treatment. NiFe2O4 nanocatalysts could be uniformly dispersed on the highspecific-area MoS2 surface, representing a highly efficient, inexpensive, and magnetically recoverablenanocomposite catalyst. The semiconductor property of MoS2 ensures a high electric conductivity, thusenhancing electron transfer between the reductant and the reactant. Furthermore, the strong magneticcharacteristics enable its convenient separation from the reaction mixture. NiFe2O4 nanoparticles onMoS2-supported produces multiple electron transfer pathways and overcomes known drawbacks of catalyticmethods that use metals alone, endowing long-term cycle stability. Overall, MoS2/NiFe2O4 exhibitedan excellent catalytic activity and high yields in the reduction of nitrobenzene in water, maintainedeven after five cycles.

Electrochemical activity of Samarium on starch-derived porous carbon: rechargeable Li- and Al-ion batteries

Zhang Kaiqiang,Lee Tae Hyung,최민주,RAJABI ABHARI ARAZ,Choi Seokhoon,Choi Kyung Soon,Varma Rajender S.,Choi Ji-Won,장호원,Shokouhimehr Mohammadreza 나노기술연구협의회 2020 Nano Convergence Vol.7 No.11

Rechargeable metal-ion batteries are considered promising electric storage systems to meet the emerging demand from electric vehicles, electronics, and electric grids. Thus far, secondary Li-ion batteries (LIBs) have seen great advances in terms of both their energy and their power density. However, safety issues remain a challenge. Therefore, rechargeable Al-ion batteries (AIBs) with a highly reliable safety advantage and active electrochemical performances have gathered intensive attention. However, the common issue for these two metal-ion batteries is the lack of cathode materials. Many advanced electrode materials reported provide greatly enhanced electrochemical properties. However, their inherent disadvantages—such as complicated fabrication procedures, restricted manufacturing parameters, and the requirement of expensive instruments—limits their potential for further applications. In this work, we demonstrate the high electrochemical activity of the lanthanide element, Sm, towards storing charges when used in both LIBs and AIBs. Lanthanide elements are often overlooked; however, they generally have attractive electrochemical properties owing to their unpaired electrons. We employed starch as both a low-cost carbon source and as a three-dimensional support for Sm metal nanoparticles. The composite product is fabricated using a one-pot wet-chemical method, followed by a simultaneous carbonization process. As a result, highly improved electrochemical properties are obtained when it is used as a cathode material for both LIBs and AIBs when compared to bare starch-derived C. Our results may introduce a new avenue toward the design of high-performance electrode materials for LIBs and AIBs.

Magnetically retrievable nanocomposite adorned with Pd nanocatalysts: efficient reduction of nitroaromatics in aqueous media

Shokouhimehr, Mohammadreza,Hong, Kootak,Lee, Tae Hyung,Moon, Cheon Woo,Hong, Seung Pyo,Zhang, Kaiqiang,Suh, Jun Min,Choi, Kyoung Soon,Varma, Rajender S.,Jang, Ho Won The Royal Society of Chemistry 2018 Green chemistry Vol.20 No.16

<P>Herein, we describe the fabrication of a magnetically retrievable nanocomposite adorned with highly active Pd nanoparticles (NPs) (MRN-Pd), which is useful for the efficient reduction of nitroaromatics in aqueous solution. The polymerization of pyrrole as the monomer in the presence of Pd salt and iron nanopowder generates Pd nanocatalysts and localizes the resultant Pd NPs discretely and uniformly on the polypyrrole framework comprising strongly magnetic MRN-Pd catalyst without the need for any reducing agent. The nitrogen-containing polymer enhances the interaction between the decorated Pd nanocatalysts and the polymer scaffold, endowing stability to the Pd NPs and maintaining their monodispersity. This prevents the possible aggregation of the MRN-Pd catalyst and promotes its reactivity for fast reduction processes. The unique features exhibited by the MRN-Pd catalyst result in excellent catalytic activity for the expeditious reduction of nitroaromatics under green reaction conditions at room temperature. Furthermore, the pronounced magnetic characteristics of the MRN-Pd catalyst allow its convenient separation and recycling from the reaction mixture. In addition, the MRN-Pd catalyst can be completely separated and recycled using a small magnet and reused for seven consecutive cycles of high-yield reduction of nitrobenzene (99-95%) in water, thus affording a highly retrievable and sustainable magnetic nanocomposite catalyst suitable for environmentally friendly processes. The MRN-Pd catalyst also presents high catalytic activity in other typical catalytic transformations requiring Pd nanocatalysts, such as the Suzuki and Heck cross-coupling reactions.</P>