Currentevoltage characteristics of electrochemically synthesized multi layer graphene with polyaniline

The ACNPs catalyst was synthesized based on the CuFe2O4nanoparticles by the incorporation of Ag atoms, which showed an excellent 97% photocatalytic activity as compared to the host CuFe2

Original Article

cyclic voltammetry and photocatalytic studies

B.S Surendra

Department of Chemistry, East West Institute of Technology, Bengaluru 560 091, India

a r t i c l e i n f o

Article history:

Received 17 December 2017

Received in revised form

25 January 2018

Accepted 27 January 2018

Available online 6 February 2018

Keywords:

Jatropha-oil

AgeCuFe 2 O 4

CuFe 2 O 4

CV and EIS

Photocatalysis

a b s t r a c t

Ag-doped CuFe2O4nanoparticles (ACNPs) with cubic and tetragonal spinel structures were synthesized

by the Jatropha-oil assisted combustion method and their properties were well characterized The ACNPs catalyst was synthesized based on the CuFe2O4nanoparticles by the incorporation of Ag atoms, which showed an excellent (97%) photocatalytic activity as compared to the host CuFe2O4(85%) under UV-light for the decomposition of Malachite green (MG) dye Electrochemical properties of CNPs were studied by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) Our study provides some new insights into the design of materials for multifunctional long-term applications The prepared photocatalysts exhibited reusability with an excellent efficiency

© 2018 The Author Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

The non-edible plant seed cakes are the most abundant

renewable biomasses and sustainable alternative source for

chemicals The non-edible plant seeds like, Jatropha, Pongamia,

Simarubha etc were used in the production of biodiesel by

extracting the oil During this process, it released huge amount of

seed cake, which contains little oil, proteins, carbohydrates,fiber

and inorganic compounds[1e5] Therefore, it has been used for

extracting the smaller percentage of oil and used as a fuel for the

synthesis AgeCuFe2O4using the combustion method

Nowadays many industries and laboratories use carcinogenic

coloring reagents, releasing waste water and thus causing a lot of

problems to the environment Mainly the dye discharge into water

from industries is extremely toxic to microorganisms, aquatic life

photo-catalysts used for the treatment of organic pollutants can utilize

ultraviolet radiations due to their intrinsic limitations of band gap

(> 3.1 eV) To deal with this issue, we need to develop a

photo-catalyst that efficiently extends its visible light response in catalytic

activities for environmental remediation This has become a great

task and one of the most dynamic research topics in photocatalysis

[11e13] In this regard, spinel ferrites MFe2O4(M¼ Mn, Zn, Cu etc.)

and their related structures have been researched for their photo-catalysis and magnetic properties [14e16] Also, ferrite

technological importance in high density magnetic storage, tele-communication equipment, gas sensors, and etc.[17,18] Doping adds intentional defects into the host particles that may have a

reflective effect in a photocatalysis reaction Potential toxicity of metals is one of the fundamental concerning issues while deciding the doping substances However, Ag metal possesses an eco-friendly, antimicrobial and antioxidant property, which affects the properties of CuFe2O4nanoparticles by doping of Ag, therefore a combination of these two may yield an excellent photocatalytic activity A material that possesses properties like good stability, high reactivity and ability to be magnetically separated can be applied in a wide range offields

In the present investigation, Ag-doped CuFe2O4and host CuFe2O4 photocatalysts were fabricated by the combustion method and the properties were well characterized by various techniques These photocatalysts are promising for multifunctional applications

2 Experimental 2.1 Extraction of Jatropha oil The Jatropha oil was extracted by Soxhlet extraction method

E-mail address: surendramysore2010@gmail.com

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2018.01.005

2468-2179/© 2018 The Author Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license

Journal of Science: Advanced Materials and Devices 3 (2018) 44e50

heating mantle till up to 45 cycles at 70C followed by distillation

composition of extracted Jatropha oil was analyzed using BTH/QL1/

161 instrument and the details were given inTable 1

2.2 Synthesis of Ag-doped CuFe2O4nanoparticles (ACNPs)

The CuFe2O4NPs was prepared by using stoichiometric amounts

of analytic grade Cu (NO3)2$3H2O and Fe (NO3)3$9H2O and an

optimal amount of extracted Jatropha oil was used as a green fuel

The above mentioned materials were taken in a crucible with

minimum quantity of double distilled water and magnetic stirrer,

mixed thoroughly to attain homogeneity and placed in a preheated

preparation, the optimum amounts of Ag(NO3) (2 wt%)[20]were

obtained by using Jatropha oil as a green fuel, and the same

pro-cedure was followed to get thefinal product

2.3 Characterization

The phase investigation of the prepared materials was carried

out in Shimadzu Powder X-ray diffractometer (PXRD) using nickel

filter in the range 20e70with Cu Ka(1.541 Å) radiation at a scan

rate of 2 min1 Using AXIS ULTRA from AXIS 165, the surface

morphology was studied using SEM, Hitachie 3000 FT-IR studies

were performed with a Spectrum-1000 (Perkin Elmer)

spectro-photometer UVeVisible absorption was recorded using Shimadzu

UV 2600 UVeVisible Spectrophotometer The surface area and pore

using Quanta chrome Nova-1000 surface analyzer under a liquid

nitrogen temperature regime

2.4 Photocatalytic activity studies

The photocatalytic decomposition of dye was carried out under

UV-light for the synthesized ACNPs and CNPs by degrading

Mala-chite green (MG) dye Here, 30 mg of synthesized ACNPs dispersed

in 250 ml of MG dye solution was taken in a glass reactor During the

experiment, 5 ml of dye solution was pipetted out at regular

in-tervals until a complete decomposition of the dye solution and

finally the adsorption was observed using UVeVisible

spectropho-tometer In order to check the endurance of the synthesized ACNPs,

the experiment was repeated by using the same photocatalyst after

washing and drying it with fresh dye The concentration of MG was

analyzed by monitoring the absorbance at 617 nm

3 Results and discussion 3.1 PXRD analysis The PXRD patterns of the prepared ACNPs and CNPs are shown in

Fig 1 The PXRD pattern shows the major reflection peaks indexed as (220), (311), (111), (400), (200), (422), (511) and (440), and these peaks well matched with JCPDS card No 034-0425 having the cubic and tetragonal spinel structures[21] In ACNPs, the existence of the extra peaks indicated that the Ag has been incorporated in the host CuFe2O4NPs The crystallization process proceeded along the (311) and (440) crystal planes and the intensity of these planes was found

to be minimum for the CNPs as compared to the ACNPs Scherer's method was employed to observe the variation in crystallite size for the prepared ACNPs[22] The estimated results showed that the average crystallite size is ~16 and ~20 nm for the prepared CNPs and ACNPs, respectively

3.2 Morphological studies

Fig 2shows the SEM micrographs of the ACNPs and CNPs pre-pared by the combustion method In this method, the temperature was uniformly distributed and transferred to the interior of the sample, which made the evolution of gases and release of enor-mous amount of heat to form spinel ferrites[23].Fig 2(a) shows the spinel structure with porousflakes and agglomeration of particles, whereas in case of the Ag-doped sample it showed the change in morphology by the formation of numerous trapped pores, and spherical shaped agglomerations were observed [Fig 2(b)] When ferric nitrate was mixed with copper ferrite in the presence

of Jatropha oil extract, the Cu2þand Fe2þions distributed uniformly and formed a complex structure with active fatty acids like oleic acid (Fig 3) After the complex structure reacted with proteins at a low temperature to form the superstructure When subjected to heat treatment, this network underwent slow decomposition In sum-mary, fatty acid molecules that interacted with divalent Cu2þcations forming bridges between two hydroxyl groups from two different chains came in close contact This polymeric binding was responsible for the conjugation of all these families of compounds present in the oil extract and expected to get different structures

3.3 FT-IR studies

In order to confirm the phase transformation of the prepared Ag-doped CNPs and CNPs, the FT-IR spectra were recorded in the

Table 1

Percentage composition of acid present in Jatropha oil.

Methyl esters of

range of 400e4000 cm1 (Fig 4) The two prominent absorption

tetrahedral and octahedral complexes The bond observed at

~528 cm1was attributed to the stretching vibration of the

tetra-hedral group Cu2þeO2and the bond observed at ~418 cm1was

attributed to the octahedral complex Fe3þeO2 vibrations[24,25].

attributed to the OeH bending vibration of adsorbed water

mole-cules The bond around 1100 cm1due to CeC bending frequencies

and that may correspond to the fuel Jatropha oil

3.4 Electrochemical studies

Cyclic voltammetry (CV) was examined to study the

electro-chemical properties of the synthesized Ag-doped CNPs and CNPs

carried out with a conventional three electrode system in 1 M

NaNO3electrolyte, and the results are shown inFig 5 It is worth

noting that the synthesized Ag-doped CNPs modified the electrode

Fig 2 SEM micrographs of the synthesized ACNPs and host CNPs.

Fig 3 The probable mechanism of formation of the ACNPs and host CNPs.

Fig 4 FT-IR spectra of the synthesized ACNPs and host CNPs B.S Surendra / Journal of Science: Advanced Materials and Devices 3 (2018) 44e50

46

possess redox peak with an enhanced peak current as compared to

the host CNPs, and this can be ascribed to its good photocatalytic

activity From the above explanation, it is clear that the

CNPs> the host CNPs

Fig 6 shows typical EIS (Electrochemical Impendence

Spec-troscopy) Nyquist plots of the prepared Ag-doped CNPs and CNPs

The arc radius of the EIS spectra reflects the interface layer

resis-tance arising outside the electrode The smaller the arc radius, the

higher the charge transfer effectiveness The arc radii for the

Ag-doped CNPs and CNPs were found to be 8 and 14U, respectively

This suggests that the Ag-doped CNPs has a lower charge transfer

resistance than that of the CNPs, which can accelerate the

interfa-cial charge-transfer process The smaller charge-transfer resistance

provides more contribution to the enhanced photocatalytic activity

via the easy transfer of charge Thus, the Ag-doped CNPs possess a

smaller arc radius with an enhanced photocatalytic activity as

compared to the host CNPs

3.5 Diffuse reflectance spectroscopy (DRS) analysis

Fig 7shows the DRS of the Ag-doped CNPs and CNPs tofind

(equivalent to the absorption coefficient) in Y-axis and energy in

repre-sented as follows:

FðRÞ ¼ð1  RÞ2

electron excitation from the valance band to conduction, which is determined by the following relation:

where n¼ 2 for a direct allowed transition, n ¼ 1/2 for an indirect allowed transition, A is the constant and hyis the photon energy

In order to get the direct band gap, the linear part of the curve was extrapolated to (F(R) hy)2 ¼ 0 The band gap energy (Eg) values are estimated from the plot and found to be 1.6 and 2.15 eV for the Ag-doped CNPs and host CNPs, respectively The expected changes in the band gap values in the Ag-doped CNPs are due to

BursteineMoss effect[27] 3.6 BET analysis

The N2adsorptionedesorption measurement at a liquid nitro-gen temperature of 77 K was used to study the porosity and textural properties of the synthesized Ag-doped CNPs and CNPs The combustion-derived products usually have a large surface area due

to liberation of heat (exothermicity) During combustion reaction, the temperature is just enough to form nuclei but too short for grain growth The BET surface area of the Ag-doped CNPs and CNPs were found to be 15 m2/g and 30 m2/g, respectively, as shown in

Fig 8 The large surface area of the formed sample is due to the uniform distribution of nanosized particles as observed in the SEM images, and the same may also be supported by the XRD analysis Inset ofFig 8shows the average pore diameter and isotherms for the Ag-doped CNPs and CNPs, respectively It is clear that all isotherm curves reach a plateau as the relative pressure reaches unity[28] This indicates that the materials prepared have no pores

in the macropore region (i.e., 500 Å) and means pores are in the mesopore region, and the sample is mesoporous

Fig 5 CV plots for the prepared ACNPs and host CNPs.

Fig 7 Wood and Tauc's plot to find band gap and the variation of the band gap of the ACNPs and host CNPs Inset shows the transmittance vs wavelength of the ACNPs and host CNPs.

3.7 Photocatalytic activity

The photocatalytic decomposition of MG dye was carried out for

the prepared Ag-doped CNPs and CNPs (Fig 9a and b) The

Ag-doped CNPs photocatalyst displays the best performance due to

the uniform structure with less particle size, the increase in amount

of dispersion of particles per volume, the increase in number of active sites as compared to other samples Hence, the particle size also plays an important role in the catalytic activity[29] It was found that the photo-decolorization of MG for CNPs (GCR) was 97%, whereas it was only 85% for CNPs (Fig 9c) As band gap decreases there will be an increase in the redox potential of the photo-excited electronehole pairs, thus significantly increasing the activity of the photocatalyst

3.7.1 Mechanism of MG dye decolorization The mechanism involved in the photocatalytic activity of MG dye under UV light is proposed inFig 10 On the surface of the photocatalyst, oxygen molecules (O2) and water molecules (H2O) are absorbed easily owing to the porous spinel structures under UV light irradiation These molecules are not only adsorbed on the outer surface but also adsorbed on the internal surface of the CNPs

As mentioned above, the porous structure is mainly responsible for the absorption of the aforementioned molecules and the capture of incident light When CNPs absorb photons with sufficient energy, these electrons (e) jump into the conduction band (CB) from the valence band (VB), leaving behind the same number of holes (hþ)

in the VB If these photogenerated electrons and holes become free, they automatically move towards the surface of the CNPs and are got captured by absorbed O2, OH Of course, the absorbed MG molecules can also capture the carriers to ionize it After that, a lot

of superoxide radicals (O2) and hydroxyl radicals (OH) are formed These produced active radicals react with the ionized MG mole-cules to decompose them into the harmless H2O, CO2, and mineral

Fig 9 (a) % decomposition of MG under UV light for the synthesized host CNPs; (b) % decomposition of MG under UV light for the synthesized ACNPs; and (c) Spectral absorbance

Fig 8 Nitrogen adsorption and desorption isotherms and pore volume distribution

curves (inset) of the synthesized ACNPs and host CNPs.

B.S Surendra / Journal of Science: Advanced Materials and Devices 3 (2018) 44e50 48

acids (NO2 , NO

3

, or SO

4 )[30e32]During this step, partial strong oxidizing holes (hþ) can also directly participate in the

decompo-sition of the MG molecules According to the results obtained, the

self decomposition of MG molecules is very negligible

4 Conclusion

The present work demonstrated the efficient ability of preparing

the Ag-doped CNPs with enhanced photocatalytic properties by

using the Jatropha-oil assisted low temperature combustion

method The PXRD analysis clearly confirms the formation of cubic

and tetragonal phases with an average crystallite size of around

12 nm The energy band gap (Eg) values of the Ag-doped CNPs and

host CNPs samples were found to be 1.6 and 2.15 eV, respectively The

electrochemical properties of the synthesized samples possess the

redox peak with an enhanced peak current, and the arc radii of the

Ag-doped CNPs and CNPs were found to be 8 and 14Urespectively

This indicates that the Ag-doped CNPs has a lower charge transfer

resistance with enhanced photocatalytic activity The photocatalytic

activity of the Ag-doped CNPs is highly active towards the

photo-decolorization of MG with a very high yield (97%), due to the

smaller crystalline size, the lesser band gap, and the presence of

more number of active sites These synthesized photocatalysts are

also recoverable and recyclable

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