Microwave-mediated synthesis of spinel CuAl2O4 nanocomposites for enhanced electrochemical and catalytic performance

Article abstract of DOI:10.1007/s11164-017-3213-z

Abstract: The present study explores synthesis of spinel copper aluminate nanocomposites (CuAl₂O₄ NCs) for electrochemical applications and solvent-free synthesis of xanthanedione derivatives. CuAl₂O₄ NCs were s

Full text of DOI:10.1007/s11164-017-3213-z

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Res Chem Intermed
https://doi.org/10.1007/s11164-017-3213-z
Microwave-mediated synthesis of spinel CuAl2O4
nanocomposites for enhanced electrochemical
and catalytic performance
Ratiram Gomaji Chaudhary1
Vaishali N. Sonkusare2
•
•
Ganesh S. Bhusari3 Aniruddha Mondal4 Dadamia PMD Shaik5
Harjeet D. Juneja2
•
•
•
Received: 8 September 2017 / Accepted: 17 November 2017
Ó Springer Science+Business Media B.V., part of Springer Nature 2017
Abstract The present study explores synthesis of spinel copper aluminate nanocom-
posites (CuAl2O4 NCs) for electrochemical applications and solvent-free synthesis of
xanthanedione derivatives. CuAl2O4 NCs were synthesized from copper nitrate and
aluminum nitrate with/without use of sodium dodecyl sulfate (SDS) by aqueous pre-
cipitation and microwave-assisted (MW) technique. As-synthesized CuAl2O4 NCs were
characterized structurally and morphologically using X-ray diffraction (XRD) analysis,
Fourier-transform infrared (FT-IR) spectroscopy, diffuse reflectance spectroscopy
(DRS), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy
(XPS), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron
microscopy (TEM), and atomic force microscopy (AFM). Formation of cubic spinel
structure after calcination at 900 °C was confirmed by XRD analysis, while Raman, XPS,
and EDS validated the composition and purity. TEM revealed that the particles had uni-
form nanosphere shape with average size of 10 nm for microwave-assisted with surfactant
(MWS-CuAl2O4), while aqueous precipitation with surfactant (APS-CuAl2O4) NCs
exhibited nanograins with particle size of 17 nm. AFM revealed higher surface roughness
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11164-
017-3213-z) contains supplementary material, which is available to authorized users.
&
Ratiram Gomaji Chaudhary
chaudhary_rati@yahoo.com
1
2
3
4
5
Post Graduate Department of Chemistry, Seth Kesarimal Porwal College of Arts, Commerce
and Science, Kamptee 441001, India
Post Graduate Teaching Department Chemistry, Rashtrasant Tukadoji Maharaj Nagpur
University, Nagpur 440033, India
Department of Chemistry, Visvesvaraya National Institute Technology (VNIT),
Nagpur 440010, India
Discipline of Inorganic Materials and Catalysis, Academy of Scientific and Innovative
Research, CSIR-Central Salt and Marine Chemical Research Institute, Bhavnagar 364002, India
Department of Physics, Sree Vidhyaniketan Engineering College, Tirupati 517102, India
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R. G. Chaudhary et al.
for MWS-CuAl2O4 NCs than APS-CuAl2O4 NCs. The electrochemical performance of the
CuAl2O4 NCs was examined in aqueous Na2SO4 (1 M) as electrolyte using cyclic
voltammetry (CV), revealing that the MWS-CuAl2O4 NCs demonstrated high specific
capacitance (125 F g-1 at current density of 0.5 mA cm-2). Furthermore, one-pot, facile,
eco-friendly MWS-CuAl2O4 NC-catalyzed synthesis of xanthanediones was developed,
exhibiting excellent yield and reusability with negligible reduction in efficiency even after
four consecutive cycles.
Graphical Abstract MWS-CuAl2O4 NCs showed enhanced electrochemical and
catalytic performance.
Keywords Spinel CuAl2O4 NCs Á Microwave-assisted technique Á Electron
microscopy Á Nanospheres Á Electrochemical performance Á Heterogeneous
catalyst
Introduction
Nowadays, heterogeneous catalysts are attracting much attention from the scientific
community due to their diverse properties and applications [1–8]. Among such
materials, spinel copper aluminate nanocomposites (CuAl2O4 NCs) are materials of
interest due to their non-toxic nature, low-cost, high thermal stability, high
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Microwave-mediated synthesis of spinel CuAl2O4…
mechanical strength, hydrophobicity, and low surface acidity [9], characteristics
that make them widely applicable in various fields, e.g., as photocatalysts for
degradation of organic pollutants, as magnetic materials, in rechargeable batteries,
for organic transformations, in medicine, and for recycling of nuclear fuel [10–12].
Various methods, including solid-state, co-precipitation, hydrothermal, sono-
chemical, reverse microemulsion, sol–gel reaction, and microwave technique, have
been employed for preparation of CuAl2O4 NCs [13–18]. Among these methods, the
microwave approach is a valuable and attractive technique for preparation of
CuAl2O4 NCs, due to its high reaction rate, short reaction time, high yield, and
selectivity [18]. Also, it produces pure and ultrafine powder at relatively low
temperature because of its different heating mechanism compared with conventional
techniques, opening up prospects for manufacture of diverse materials in very short
time with high energy efficiency [19]. Numerous researchers have prepared
different aluminate nanocomposites, including CoAl2O4, Co:ZnAl2O4, ZnAl2O4,
MgAl2O4, ZnAl2O4/ZnO, Ni–MgX–Al2O3, SrAl2O4, etc., using microwave-assisted
technique [20–25].
Synthesis of xanthenediones is an ongoing hot topic of research, due to their use
as pharmacophores and valuable reactive intermediates in both synthetic and
medicinal chemistry [26]. However, development of eco-friendly methods for
synthesis of xanthenedione derivatives remains a challenge. Various researchers
have reported CuAl2O4 NCs for photocatalytic degradation of methyl orange
[9, 27]. Kwak et al. synthesized CuAl2O4 NCs via a sol–gel method for
hydrogenolysis of glycerol [13]. However, there is only a single report on
microwave combustion preparation of spinel CuAl2O4 NCs for catalytic oxidation
of benzyl alcohol [18]. To the best of the authors’ knowledge, the electrochemical
properties of CuAl2O4 NCs also remain unexplored. Furthermore, no reports are
available on solvent-free green synthesis of xanthanediones using microwave-
irradiated CuAl2O4 NCs as catalyst.
The authors previously reported preparation of new, efficient, reusable copper
and alumina as nanocatalysts for fabrication of chromene derivatives and
dihydropyrimidinones, respectively [28, 29]. In the work presented herein, spinel
CuAl2O4 NCs were synthesized by adopting aqueous precipitation (AP) and
microwave-assisted (MW) techniques with/without use of SDS as surfactant. As-
synthesized NCs were characterized by various techniques including XRD analysis,
FT-IR spectroscopy, DRS, EDS, XPS, Raman spectroscopy, SEM, TEM, and AFM.
Furthermore, the electrochemical performance of the synthesized NCs was
investigated. The prepared MWS-CuAl2O4 NCs were then used as nanocatalyst
for synthesis of xanthenediones, and reaction conditions including time, temper-
ature, and solvents were optimized, and their reusability investigated.
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R. G. Chaudhary et al.
Experimental
Materials and methods
Copper nitrate trihydrate [Cu(NO3)2Á3H2O], aluminum nitrate nonahydrate
[Al(NO3)2Á9H2O], sodium hydroxide (NaOH), sodium dodecyl sulfate (SDS), and
sodium sulfate (Na2SO4) were procured from Sigma-Aldrich (Germany).
Polyvinylidene fluoride (PVDF), acetone, ethanol, ethyl acetate, chloroform, N-
methyl-2-pyrrolidone (NMP), and dichloroethane were purchased from Merck
(India). All chemical reagents were of analytical grade and used without further
purification.
Synthesis of CuAl2O4 NCs
CuAl2O4 NCs were synthesized from Cu(NO3)2Á3H2O and Al(NO3)2Á9H2O at molar
ratio of Cu/Al = 1:2 with/without use of SDS as surfactant by AP and MW-assisted
methods. Aqueous solution of Cu(NO3)2Á3H2O (0.1 M) and Al(NO3)2Á9H2O
(0.2 M) was prepared by dissolving separately in deionized water. Then, both
solutions were transferred into a round-bottomed flask (RBF), and stirred well by
magnetic stirrer until clear blue solution formed. Afterward, freshly prepared NaOH
(0.6 M) and SDS (0.1 N) solution was added, and the reaction mixture was
maintained at 60 °C for 2 h. Then, chocolate-brown precipitate was obtained, which
was separated by centrifugation and further washed with distilled water, ethanol,
and acetone. NCs synthesized by aqueous precipitation technique with and without
SDS are denoted as APS-CuAl2O4 and AP-CuAl2O4, respectively.
In addition, Cu(NO3)2Á3H2O (0.1 M) and Al(NO3)2Á9H2O (0.2 M), NaOH
(O.6 M), and SDS (0.1 M) were taken in a RBF. Then, the mixture was placed in
a microwave (Sinero, 1 kW) for 10 min for irradiation. Chocolate-brown precipitate
was obtained, which was separated using the above-mentioned filtration and
washing procedures. NCs prepared with and without use of SDS by MW-assisted
technique are denoted as MWS-CuAl2O4 and MW-CuAl2O4, respectively. After
washing, as-synthesized NC precipitates were dried in a vacuum oven at 80 °C for
24 h. Then, vacuum oven-dried CuAl2O4 NCs (AP-CuAl2O4), APS-CuAl2O4, MW-
CuAl2O4, and MWS-CuAl2O4) were calcined at 900 °C for 2 h to achieve
nanosized dimension. A flowchart of the synthesis of CuAl2O4 NCs through AP and
MW-assisted techniques is presented in Scheme 1.
Characterization techniques
X-ray diffraction (XRD) measurement was performed on a Bruker AXS D8
Advance diffractometer in the 2h range from 20° to 80° using Cu Ka radiation at
k = 0.154 nm. Fourier-transform infrared (FT-IR) spectra were recorded in the
range from 400 to 4000 cm-1 on a Bruker IFS 66v spectrophotometer having
4.0 cm-1 resolution by KBr pellet technique. Qualitative elemental analysis was
performed using energy-dispersive X-ray spectroscopy (EDS; Oxford Instrument).
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