Controlled Synthesis of NiO and Co3O4 Nanoparticles from Different

Subscriber access provided by TUFTS UNIV

Article

Controlled synthesis of NiO and Co3O4 nanoparticles from different coordinated precursors: The impact of precursor's geometry on the nanoparticles characteristics Metwally Madkour, Yasser K. Abdel-Monem, and Fakhreia Al Sagheer Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 23 Nov 2016 Downloaded from http://pubs.acs.org on November 23, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Controlled synthesis of NiO and Co3O4 nanoparticles from different coordinated precursors: The impact of precursor's geometry on the nanoparticles characteristics Metwally Madkoura*, Yasser K. Abdel-Monemb*, Fakhreia Al Sagheera a

Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait. b Chemistry Department, Faculty of Science, Menoufia University, 32511 Shebin El-Kom, Egypt. Abstract Metal oxide nanoparticles are of great technological relevance because of their wide applications in catalysis and photonics. Herein, we report a one-pot method to synthesize transition metal oxide nanoparticles such as NiO and Co3O4 via solid state thermal decomposition of its analogue coordinated metal precursors without stirring and washing. The significance of the reported method represented in its purity without washing and the systematic production. The impact of precursor structure on the characteristics of the nanoparticles was investigated. Variation of the precursor geometry affected the morphology of the nanoaprticles from spherical to pyramidal upon changing the geometry from octahedral to square-pyramid, respectively. The synthesized nanoparticles were characterized by XRD, XPS, N2 Sorpometry, UV-Vis and SEM. The photocatalytic activity of the prepared nanoparticles was assessed toward the photodegradation of Methylene Blue dye as a model pollutant. The nanoparticles exhibited superior photocatalytic efficiency in the trend of NiO ˃ Co3O4. The morphology-photo efficiency relationship was investigated. The reported method herein would provide a potential facile route for fabricating other metal oxides with controllable morphology.

Keywords: Nanophotocatalyst; Metal Oxide; Complex geometry; photodegradation * Corresponding authors:

E-mail address: [email protected] (Metwally

Madkour). Tel.: +965 90942431; fax: +965 4816482. [email protected] (Yasser Abdel-Monem)

1 Environment ACS Paragon Plus


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. Introduction Transition metal oxide nanoparticles are used in various fields such as sensors, catalysis, photocatalysis and photovoltics due to its optoelectronic characteristics [1, 2]. Researchers paid a great concern for synthesis of metal oxide nanoparticles with uniform particle size and morphology which represents a great challenge [3, 4]. Among transition metal oxides, NiO and Co3O4 are p-type semiconductor metal oxides having a wide band gap Eg ≅ 3.62 eV for NiO and both direct and indirect band gaps of Eg ≅ 2.10 eV and Eg ≅ 1.60 eV for Co3O4 [5, 6]. Large number of potential applications of NiO and Co3O4 lead many material scientists to investigate the introduction of metal oxides into novel nanomaterials with valuable properties for future applications. These potential applications depend mainly on the extend of sizecontrolled, uniform, monodispersed and well crystalline nanomaterials. Considerable efforts have been paid to synthesize individual metal oxide such as NiO [7–9] and Co3O4 [10–12]. Among various synthetic methods for the preparation of metal oxide nanoparticles, the thermal decomposition of single molecular precursors has received considerable interest rather than multiple reactants [13-17]. The main advantage of this technique over the other methods is represented in its simplicity without any need for extra purification steps and guarantee fixed stoichiometry of the final decomposition products [18]. One more advantage, the intermediates of thermal decomposition process of molecular precursors, act as protecting agents and assist in the formation of nanoparticles with unique morphologies [19]. It is proposed that the crystal structure of the selected precursor will have a strong impact on the crystal structure of the metal oxide nanoparticles [20-22]. To the best of author's knowledge, only few reports are available on the thermal decomposition of single source precursors for synthesis of NiO and Co3O4 NPs and none of them investigated the effect of the coordinated precursor geometry on the morphology of the synthesized nanoparticles. The investigation of the effect of single molecular precursor's geometry on the morphology of nanoparticles is the main target of this study. Reported is a cost effective and generalized synthetic route for the preparation of Co3O4 and NiO nanoaprticles from novel coordinated precursors. The currently reported method could be fairy regarded as one of the simplest and systematic methods of nanoaprticles preparation. As most of the reported methods failed to pre-control the morphology of the particles and the applications of nanoaprticles are mainly size- and shape- dependent, this study investigated how metal to ligand bonding and geometry of the complex can be manipulated to control the size and morphology of transition metal oxide nanoparticles. Finally the photocatalytic activity of the synthesized nanoparticles was assessed for MB dye removal and the 2 Environment ACS Paragon Plus

Page 2 of 24

Page 3 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


morphology-photo efficiency relationship was investigated. 2. Experimental 2.1 Synthesis of metal oxide nanoparticles Transition metal oxide nanoparticles were obtained from the autocatalytic decomposition of their respective precursors. For Co3O4 precursors, 2,5-hexanedione bis(salicyloylhydrazone) cobalt (II) complex as a precursor for Co3O4-I was prepared as previously reported [23], and Adipic acid dihydrazide cobalt (II) complex as a precursor for Co3O4 -II was prepared as previously reported [24]. For NiO precursors, bis(salicylaldehydato)nickel(II) complex as a precursor for NiO-I was prepared as previously reported [25], and 2-(3-Amino-4,6-dimethyl1H-pyrazolo[3,4-b] pyridin-1-yl)acetohydrazide nickel(II) complex as a precursor for NiO-II was prepared by our group (under publication). In this method, the dried precursor was transferred to a silica crucible and heated at 550 °C an ordinary atmosphere for about 60 minutes with heating rate 15 dpm according to the thermal behavior of the precursors. The precursor started decomposing violently. The total decomposition of the precursor complex led to the formation of the corresponding oxide nanoparticles, which are quenched to room temperature, ground well, and stored.

2.2 Characterization of nanoparticles The X-ray diffraction (XRD) measurements were conducted by using X’Pert PRO Panalytical diffractometer with copper target and nickel filter with CuKα radiation (λ = 0.154 nm). Measurements were performed in the range 20-80° (2θ). The morphology of the particles, as well as electron diffraction patterns were obtained by Scanning electron microscopy (SEM) using JEOL JSM-7001F operating at 120 kV. Optical properties were investigated using UV-visible absorption spectroscopy on Shimadzu UV2450 spectrophotometer. X-ray photoelectron spectroscopy (XPS) surface elemental analysis was conducted using a model Thermo ESCA Lab 250xi equipped with MgKα radiation (1253 eV) and operated at 23 kV and 13 mA. The binding energy was referenced to C1s line at 284.76 eV for calibration. The chemical composition of the surface was obtained by comparing the peak areas of their spectra. 2.3 Photocatalytic Activity



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 24

Methylene blue was used as representative of organic pollutant to evaluate the photocatalysts. In a 250 ml beaker 0.01 g of the catalyst was dispersed in 100 ml of 0.01 g/l methylene blue aqueous solution. The powder was dispersed in the solution dye using ultrasonic bath for 10 minutes in dark afterward. After another 15 minutes of stirring in dark, to achieve adsorption–desorption equilibrium with catalyst, the zero measurement was taken then the solution was irradiated with 254 nm UV lamb while stirring. 5 ml from the solution was taken on regular intervals to monitor absorbance change. The samples taken were centrifuged at 5000 rpm for 30 minutes to remove the catalyst before measuring the absorbance.

3. Results and discussion 3.1 Thermal studies The TGA curve of 2,5-hexanedione bis(salicyloylhydrazone) cobalt (II) complex as a precursor for Co3O4-I nanoaprticles is shown in fig. S1 displayed the 1st and 2nd decomposition steps at 127 and 254 °C are due to the removal of C2H5OH + H2O. The 3rd step at 549 °C indicates the decomposition of the organic ligand leaving Co3O4 as a residual part 14.41%. The DTG curve shows all the decomposition processes characterized by endothermic reaction at Tmax (127, 254, 549 ºC). The formation of Co3O4-I nanoaprticles as a result of the thermal degradation is shown in Scheme 1.

CH3

H3C

CH3

H3C

H2O

H2O N OH

N

N Co

o

N

OH

30-75 C 3.77%

N OH

N

O

O

N Co

N

OH

O

O

H2O o 21.36% 75-225 C

N OH (15.39%) 1/3Co3O4

N

225-800oC

N Co

O

N

OH

O

59.48%

Scheme 1: Mechanism of formation of Co3O4 I The TGA curve of Adipic acid dihydrazide cobalt (II) complex as a precursor for Co3O4 –II nanoaprticles is shown in Fig. S2 displayed a first step up to 200°C with weight loss of 9.66% 4 Environment ACS Paragon Plus

Page 5 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


revealing the removal of two water molecules. The second step with 18.74% weight loss corresponding to the removal of H2O + Cl2. The third and fourth steps with 12.40% and 16.43%, respectively which are associated with the complete degradation of the organic ligand. The final step is corresponding to Co3O4 as a residual part 21.09%. However, Jeragh et. al [24] reported that the residue was found to be 15.94% which is corresponds to Co metal. This difference is originated from the conditions of thermal analysis as they conducted under nitrogen instead of air in the present study. Therefore, the extra oxygen atoms of the cobalt oxide came from the atmosphere. The formation of Co3O4-II nanoaprticles as a result of the thermal degradation is shown in Scheme 2. O

O

H N HN

N H

O

NH2 .2H2O

30-78 oC 10.05%

H N HN

Co H2O

N H

O

NH2

Co Cl

H2 O

Cl

Cl Cl 5.03% 78-205oC

O

O

H N HN

N H

O Co

NH2

205-313oC 19.83%

H N HN

O

N H

NH2

Co Cl Cl

o 42.66% 313-800 C

(22.43%) 1/3Co3O4

Scheme 2: Mechanism of formation of Co3O4 II. For bis(salicylaldehydato)nickel(II) complex as a precursor for NiO-I nanoaprticles, TGA curve is shown in Fig. S3. The thermal behaviour shows first weight loss corresponding to release of H2O up to 250 ºC. Once, removal the water, the complex showed progressive decomposition within temperature range 250–366 ºC assigned to removal two nitro groups. The decomposition of organic ligand occurs in temperature range 366–435 ºC with weight loss 39.58 %. The final step is corresponding to NiO as a residual part 18.86% . The DTG curve showS all the decomposition processes characterized by endothermic reaction at Tmax (234, 310, 534 ºC). The formation of NiO-I nanoaprticles as a result of the thermal degradation is shown in Scheme 3.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 24

CH3 N

N

N

N

o

30-150 C 3.66%

Ni O

O

N

N

150-800oC NiO (18.19 %) 78.15%

Ni O

O

Scheme 3: Mechanism of formation of NiO I.

For

2-(3-Amino-4,6-dimethyl-1H-pyrazolo[3,4-b]

pyridin-1-yl)acetohydrazide

nickel(II)

complex as a precursor for NiO-II nanoaprticles, the TGA curve is shown in Fig. S4 which shows a thermal stability up to 266 ºC. Thermal decomposition took place in three stages. The first stage occurs within the temperature range 28–266 ºC corresponding to release the solvent of crystallization and decholorization. The second stage occurs in temperature range 266–416 ºC represented by removal of coordinated water and chloride associated with partial decomposition of organic ligand (CH2CONHNH2). The final stage took place in 416–788 ºC range assigned to decomposition of rest organic ligands. The DTG curve shows all the decomposition processes characterized by endothermic reaction at Tmax (237, 409, 500 ºC). The final step is corresponding to NiO as a residual part 34.92%. The formation of NiO-II nanoaprticles as a result of the thermal degradation is shown in Scheme 4. +

CH3

NH2

CH3

NH2

N H3 C

N

N

N NH .Cl.0.5H2O

C H2O O

28 266 oC 10.42 %

H3 C

N

N C O

Ni H2 O H O 2

NH H2O

NH2

NH2 Ni

Cl H2 O H O 2

Cl

[Ni(HL)Cl(H2O)3]Cl.0.5H2O o 266 416 C

45.34 % CH3

(34.92 %) 2NiO

NH2 N

416 788 oC H3 C

N

N Ni

Scheme 4: Mechanism of formation of NiO II.


+

Page 7 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.2 Optical properties UV–visible absorption spectra of the observed NiO and Co3O4 nanoparticles are shown in Fig.1. A strong absorption in the UV region is observed at a wavelength 247 nm and 254 nm for NiO and Co3O4 respectively. In this study, we calculated the band gap energy of the NPs using the Tauc equation: (αhʋ )1/m = k (hʋ − Eg)

(1)

where Eg is the optical band gap energy, k is a constant and m = 1/2 for a direct energy gap. For this purpose, a plot of (αhν)2 versus hν was constructed and the linear portion of the plot was extrapolated to the ordinate. As has been investigated in the literatures [26, 27], the Eg values of nanoparticles are greater than those of bulk NiO and Co3O4 NPs as shown on the spectra (Fig. 1). The increase in the band gap of the nanoparticles may be ascribed to the quantum confinement effects of nanomaterials. As clearly shown from the spectra a slight blue shift in the absorption behavior in NiO and Co3O4 NPs upon using different precursor structure which is mainly ascribed to the variation of particle size. This is occurring as it is known that the optical properties of nanoparticles are highly dependent on its size. Smaller nanoaprticles have peaks shifted towards shorter wavelengths (known as blue-shifting) [28]. The VB edge potential (EVB) of a ground-state semiconductor can be empirically determined by using the equation, EVB = χSemiconductor − Ee + 0.5Eg, derived using Mulliken electronegativity theory [29], where χSemiconductor is the electronegativity of the semiconductor (in this case 3.38 eV and 5.90 eV for NiO and Co3O4 respectively) [30, 31], Ee is the energy of free electrons on the hydrogen scale (ca. 4.5 eV), and Eg is the band gap energy of the semiconductor (calculated by the method described above). The CB edge potential can be determined using the relationship ECB = EVB – Eg [32, 33]. The data is tabulated in Table 1 as shown below.

Table1: values of ECB, EVB and band gaps for NiO and Co3O4. ECB, eV

EVB, eV

NiO-I

-3.06

0.82

3.88

NiO-II

-3.02

0.77

3.79

Co3O4-I

-0.44

3.24

3.68

Co3O4-II

-0.29

3.09

3.38


Eg, eV


1.0

Co3O4-I Co3O4-II

0.9 0.8

A

Absorbance

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 200 250 300 350 400 450 500 550 600 650 700

Wavelength (nm) 1.0

NiO-I NiO-II

0.9 0.8

B

0.7

Absorbance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

0.6 0.5 0.4 0.3 0.2 0.1 0.0 200 250 300 350 400 450 500 550 600 650 700

Wavelength (nm)


Page 8 of 24

Page 9 of 24

NiO-I NiO-II Co3O4-I Co3O4-II

18 15

C

2

12

(αhυ)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9

3.88 eV 3.79 eV

6

3.68 eV 3

3.38 eV

0 2.1

2.4

2.7

3.0

3.3 3.6 3.9 hυ (eV)

4.2

4.5

4.8

Fig. 1: UV-Vis spectra of (A) Co3O4 and (B) NiO nanoparticles using different precursors geometries. (C) Tauc plot for band gap determination for Co3O4 and NiO nanoparticles using different precursors 3.3 Crystal structure XRD patterns of the NiO and Co3O4 nanoparticles are shown in Fig. 2. For Co3O4 NPs, the peak positions (2θ = 31.3º, 36.88º, 44.85º, 59.41º and 65.30º) match with the JCPDS card No: 009-0418 file, identifying it as Co3O4 [34, 35]. There was no characteristic peaks of impurity were observed. The XRD pattern for NiO NPs exhibits peaks at 37.3°, 43.3°, 63°, 75.40° and 79.45°, which can be perfectly related to (111), (200), (220), (311) and (222) crystal planes, respectively. All the diffraction peaks can be indexed to a single phase of face-centered cubic NiO, matching well with JCPDS card no. 47-1049 and JCPDS card no. 004-0835 [36]. The XRD patterns for (NiO-I and NiO-II) and (Co3O4-I and Co3O4-II) nanoparticles are almost the same revealing that the change of the precursors geometry did not affect the crystal structure to much extend. The crystal size can be calculated according to Debye-Scherrer formula [37]. D=kλ/βcosθ,

(2)

Where K, a shape factor, k = 0.89 and 0.94 for spherical and pyramidal nanoparticles, λ is the wavelength of the Cu-Kα radiations, ß is the full width at half maximum and θ is the angle obtained from 2θ values corresponding to maximum intensity peak in XRD pattern. The mean crystal size of Co3O4-I and Co3O4-II nanoparticles is 5.4 nm and 4.9 nm respectively.



And the mean crystal size of NiO nanoparticles is 12.3 nm and 3.1 nm for NiO-I and NiO-II

(311)

respectively.

(440)

(511) (400)

Intensity (A.U.)

(220)

JCPDS 00-009-0418

Co3O4-II

Co3O4-I 20

25

30

35

40

45

50

55

60

65

70

(200)

2-Theta (2θ) JCPDS 00-047-1049

NiO-I

(222)

(311)

(220)

(111)

Intensity (A.U.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 24

NiO-II 20

30

40

50

60

70

2-Theta (2θ) Fig. 2: XRD patterns of Co3O4 and NiO nanoparticles using different precursors.


80

Page 11 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.4 X-ray photoelectron Spectroscopy XPS is a surface-sensitive probe that can provide valuable information on the surface composition and allow distinction of the different local atomic environments i.e., valence state and coordination of an element. Further evidence for the purity and composition of the products was obtained by X-ray photoelectron spectra (XPS). Fig. 3 shows the binding energies of Ni 2p1/2 , Ni2p3/2 ,O1s Co 2p3/2and Co 2p1/2 , provided a fairly complete picture of the sample powder. The Ni 2p3/2 XPS peak that appears at 853.4 eV and 855.2 eV and its satellite at 860.4 eV and 863.8 eV, and the Ni 2p1/2 main peak at 870.8 eV and 872.8 eV and its satellite at 877.1 eV and 880.0 eV coincides with the ﬁndings for NiO [38] . The splitting separation between these two main peaks, 17.8 eV, indicated the well-defined symmetry of the Ni(II) ion in oxide form [39]. The Co 2p region exhibits two peaks at 794.45 eV and 795.86 eV corresponding to the Co 2p1/2 and 779.42 eV and 780.46 eV corresponding to the Co 2p3/2 spin-orbit peaks of the Co3O4 phase [40, 41]. The Co 2p1/2-Co 2p3/2 energy separation is approximately 15.4 eV confirms the formation of the Co3O4 phase [42]. Weak 2p satellite features for the spinels are found at 789.1 and 804.2 eV with significantly reduced intensity compared to the intense CoO satellite peak at 802.1 eV confirms also the formation of the Co3O4 phase. A low intense satellite peak is at 789.1 eV, about 9.7 eV higher than 779.4 eV, the main peak of Co 2p3/2, It is a typical satellite peak of Co3O4 [43]. In theory, O1s region of Co3O4 and NiO should have only peak assigned to the lattice oxygen in the M-O (M = Ni or Co), appearing at 529.8 eV and at 528.8 for Co3O4 and NiO NPs, respectively. However, in reality surface of these oxides is covered with OH- and other common Oxygen containing species, hence additionally one small peak is present in the O1s region at 530.7 eV for Co3O4 and at 530.3 eV for NiO NPs (O1s figure not shown) [44].



8000

Ni 2p

Intensity (A.U.)

7000

6000

2p3/2 2p1/2 Satellite

2p3/2 Satellite

2p1/2

5000

4000

3000 885 882 879 876 873 870 867 864 861 858 855 852

Binding Energy (eV) 10000 Co 2p

2p3/2

9000 8000

Intensity (A.U.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2p1/2

7000 6000 5000

2p1/2 Satellite

2p3/2 Satellite

4000 3000 807 804 801 798 795 792 789 786 783 780 777

Binding Energy (eV) Fig. 3: Deconvoluted XPS spectra of Ni2p and Co2p.


Page 12 of 24

Page 13 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.5 SEM photo images of nanoaprticles The morphology of the synthesized nanoparticles was characterized by Scanning electron microscope (SEM). The SEM images of NiO and Co3O4 nanoparticles synthesized through thermal decomposition route are shown in Fig. 4. The SEM pictures clearly show randomly distributed NiO and Co3O4 grains with smaller size and pyramidal shaped structures with agglomeration of particles. This change in the morphology was due to the impact of the precursor structure. The table below (Table 2) summarizes the shape and particle size of different metal oxides prepared from four different complexes. For NiO and Co3O4 nanoparticles, varying the complex geometry resulted in change of the shape of the synthesized nanoaprticles. As the geometry changed from octahedral to square-pyramid, the morphology varied from semi spherical aggregations to pyramidal. The morphologygeometry relationship obtained results are in agreement with previous reports [10] in which Hosny et al. reported pyramidal shaped Co3O4 from octahedral precursor.

A

Pyrimdal

100 nm C

100 nm

B

Spherical

100 nm

Spherical

D

100 nm


Pyrimdal


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 24

Fig. 4: SEM photographs of (A) Co3O4-I (B) Co3O4-II; (C) NiO-I and (D) NiO-II nanoparticles Table 2: Characteristics of different nanoparticles from different coordinated precursors Metal oxide

Complex geometry

Coordinated complex

Shape

Crystallite size

CH3

H3 C H2 O Co3O4-

N OH

N

N Co

I

N

OH

Octahedral Spherical

5.4 nm

Squarepyramid

Pyramidal

4.8 nm

Squarepyramid

Pyramidal

12.2 nm

O

O H2 O

O H N

Co3O4-

HN

II

N H

O Co

H2O

NH2 .2H2O

Cl Cl

CH3 N NiO-I

N

N Ni O

O


Page 15 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CH3

NH2 N

H3 C

N

N NH .Cl.0.5H2O

C

NiO-II

Octahedral Spherical

H2 O O

3.1 nm

NH2 Ni

H2 O H O 2

Cl

3.6 Photocatalytic activity of transition metal oxide nanoparticles As the particle size and morphology are key factors in determining the photocatalytic activity of nanoparticles, the annealing temperature was controlled at 550°C, the temperature at which the coordinated precursors converted to their corresponding metal oxide nanoparticles as per TG/DTG curves. This is because the annealing temperature affects both factors as increasing the annealing temperature results in increasing the particle size and shape transformation [45]. The photocatalytic activities of NiO and Co3O4 nanoparticles were evaluated by monitoring the degradation of Methylene blue (MB) in an aqueous solution, under UV irradiation. Without light or nanoparticles, nearly no MB was break down after 120 min, revealing that the contribution of self-degradation was insignificant. The heterogeneous photocatalytic processes include many steps, such as diffusion, adsorption and reaction, appropriate distribution of the pore is advantageous to diffusion of reactants and products, which prefer the photocatalytic reaction [46]. Fig. 5 shows the decrease in absorption spectra of MB solution in the presence of NiO and Co3O4 photocatalysts. Under continuous irradiation conditions, the photodegradation reaction follows a pseudo-first-order rate profile that can be expressed in the form of Ln (Co/C)= − kt, where Co and C are the respective initial concentration and concentration at time t of the pollutant, and k is the apparent first-order rate constant. As a result, a plot of ln Ao/A versus time should be linear and the slope of the line should provide the apparent first-order rate constant k (Fig. 5). The rate constant of these catalytic reactions for NiO and Co3O4 were found to be 0.017/min and 0.006/min, with photodegradation efficiencies of 93% and 73% respectively. On comparing NiO shows the excellent photocatalytic activity than Co3O4 which can be attributed to the optoelectronic properties as the band gap of NiO is higher than that of 15 Environment ACS Paragon Plus


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Co3O4 which reduces the recombination possibility and enhances the photoactivity. As redox potentials of the nanoaprticles affects largely on the catalytic activity [47]. . The reactions at the NiO surface causing the degradation of dyes can be expressed as follows [48]: SC + hʋ (UV) → SC(eCB-+ hVB+)

(3)

SC(hVB+) + H2O → SC + H+ + OH•

(4)

SC(hVB+) + OH- → SC + OH•

(5)

SC (eCB-) + O2 → SC + O2-•

(6)

-•

+

O2 + H → HO2

•

•

MB + OH → degradation products MB +

hVB+

→ oxidation products

MB + eCB- → reduction products

(7) (8) (9) (10)

The crystalline nature and shape of the NiO nanoparticles plays a vital role in determining the photocatalytic activity. The different morphologies of metal oxide crystals lead to the different specific surface areas, direct band gaps and UV–Vis absorbance which cause the different photocatalytic activities [48].


Page 16 of 24

Page 17 of 24

Industrial & Engineering Chemistry Research 1.6

1.6

1.4

A 1.2

Absorbance

1.0

0.8

0.6

1.0 0.8 0.6

0.2

0.2 600

650

700

750

B

1.2

0.4

550

0 min 20 min 40 min 60 min 80 min 100 min 120 min 140 min 160 min 180 min

Co3O4

1.4

0.4

500

500

800

550

600

Wavelength, nm

100

80

650

700

750

800

Wavelength, nm 3.2

NiO Co3O4

90

NiO Co3O4

2.8

C

D

2.4

70

2.0

60

Ln Ao/A

% Degradation

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

0 min 20 min 40 min 60 min 80 min 100 min 120 min 140 min 160 min 180 min

Absorbance

NiO

50 40 30

1.6 1.2 0.8

20 0.4

10 0

20

40

60

80 100 120 140 160 180 200

0

20

40

60

80 100 120 140 160 180 200

Time, min.

Time, min

Fig.5 Absorption spectra of methylene blue dye at regular intervals in the presence of (A) NiO-I and (B) Co3O4 –I NPs. (C) Pseudo first order rate kinetics; (D) Photodegradation efficiencies using Co3O4-I and NiO-I NPs.

3.7 Morphology-Photocatalytic activity relationship The photocatalytic activity of the synthesized NiO nanoparticles was investigated measured in terms of morphology-photocatalytic activity relationship. The results shown in fig. 6 revealed that NiO-I with spherical shape (93%) is less reactive than pyramidal shaped NiO-II (97%). This phenomenon could be attributed to their aspect ratios. The aspect ratio of the NiO-I of ~1 was higher than those of NiO-II nanoparticles which is 1.6. The lower aspect ratio led to charge carrier recombination and as a result a decrease in the photocatalytic efficiency of the nanoparticles [49, 50]. One more explanation, the shape of nanoparticles has significant impact on the optical, electronic and in turn photocatalytic properties due to changes in surface area,



surface defects and number of active sites [51].

NiO-I NiO-I I

100 80

% Degradation

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

60 40 20 0

20

40

60

80 100 120 140 160 180 200

Time, Min Fig.6: MB Photodegradation efficiency using NiO-I and NiO-II NPs.

Conclusion Transition metal oxide as promising candidates for photodegradation of wastewater pollutants due to their availability and unique optoelectronic characteristics. In this study we succeed in preparation of NiO and Co3O4 via cost effective and generalized method. The impact of precursor geometry on the nanoaprticles characteristics was investigated in terms of particle size and morphology. The results revealed that as the geometry changed from octahedral to square-pyramid, the morphology varied from semi spherical aggregations to pyramidal. Finally the photocatalytic activity measurements proved the superior efficiency of the synthesized nanoparticles and the relationship between morphology and photo efficiency was understood. Supporting Information TG/DTG curve of metal complexes.


Page 18 of 24

Page 19 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References 1. Moore G. J., Portal R., Le Gal La Salle A., Guyomard D., Synthesis of nanocrystalline layered manganese oxides by the electrochemical reduction of AMnO4 (A = K, Li), J. Power Sources 2001, 97, 393-397. 2. Thackeray M. M., Kang S. H., Johnson C. S., Vaughey J. T., Benedek R., Hackney S. A., Li2MnO3-stabilized LiMO2 (M=Mn, Ni, Co) electrodes for high energy lithium-ion batteries, J. Mater. Chem. 2007, 17, 3112-3125. 3. Lee N., Hyeon T., Designed synthesis of uniformly sized iron oxide nanoparticles for efficient magnetic resonance imaging contrast agents, Chem. Soc. Rev. 2012, 41, 2575-2589. 4. Yoo D., Lee J.-H., Shin T.-H., Cheon J., Theranostic Magnetic Nanoparticles, Acc. Chem. Res. 2011, 44, 863-874. 5. Musevi S. J., Aslani A., Motahari H., Salimi H., Offer a novel method for size appraise of NiO nanoparticles by PL analysis: Synthesis by sonochemical method, Journal of Saudi Chemical Society 2016, 20, 245-252. 6. Elhag, S.; Ibupoto, Z.; Nour, O.; Willander, M., Synthesis of Co3O4 Cotton-Like Nanostructures for Cholesterol Biosensor. Materials 2015, 8, (1), 149. 7. Wang X., Song J., Gao L., Jin J., Zhengand H., Zhang Z., Optical and electrochemical properties of nanosized NiO via thermal decomposition of nickel oxalate nanofibres, Nanotechnology 2005, 16, 37-39. 8. Hosny, N. M., Synthesis, characterization and optical band gap of NiO nanoparticles derived from anthranilic acid precursors via a thermal decomposition route. Polyhedron 2011, 30, (3), 470-476. 9. Zoromba, M. S.; Hosny, N. M., Synthesis of Fe2O3, Co3O4 and NiO nanoparticles by thermal decomposition of doped polyaniline precursors. Journal of Thermal Analysis and Calorimetry 2015, 119, (1), 605-611. 10. Hosny, N. M., Single crystalline Co3O4: Synthesis and optical properties. Materials Chemistry and Physics 2014, 144, (3), 247-251. 11. Athawale A. A., Singh V., Mehta B. R., Navinkiran K., Solvent mediated morphological control of aniline stabilized cobalt oxide nanoparticles, J Alloys Compd. 2010, 492, 331-338. 12. Binitha N. N., Suraja P. V., Yaakob Z., Resmi M. R., Silija P. P., Simple synthesis of Co3O4 nanoflakes using a low-temperature sol–gel method suitable for photodegradation of dyes, J. Sol–Gel Sci. Technol. 2010, 53, 466-469. 13. Hosny N. M., Dahshan A., Synthesis, structure and optical properties of SnS2, CdS and HgS



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 24

nanoparticles from thioacetate precursor, Journal of Molecular Structure 2015, 1085, 78-83. 14. Hosny, N. M.; Nowesser, N.; Al-Hussaini, A. S.; Zoromba, M. S., Doped copolymer of polyanthranilic acid and o-aminophenol (AA-co-OAP): Synthesis, spectral characterization and the use of the doped copolymer as precursor of α-Fe2O3 nanoparticles. Journal of Molecular Structure 2016, 1106, 479-484. 15. Hosny, N. M.; Zoromba, M. S.; Samir, G.; Alghool, S., Synthesis, structural and optical properties of Eskolaite nanoparticles derived from Cr doped polyanthranilic acid (CrPANA). Journal of Molecular Structure 2016, 1122, 117-122. 16. Hosny, N. M.; Nowesser, N.; Al Hussaini, A. S.; Zoromba, M. S., Solid State Synthesis of Hematite Nanoparticles from Doped Poly o-aminophenol (POAP). Journal of Inorganic and Organometallic Polymers and Materials 2016, 26, (1), 41-47. 17. Hosny, N. M.; Al-Hussaini, A. S.; Nowesser, N.; Zoromba, M. S., Polyanthranilic acid. Journal of Thermal Analysis and Calorimetry 2016, 124, (1), 287-293. 18. Kelly A. T., Rusakova I., Ould-Ely T., Hofmann C., Lüttge A., Whitmire K. H., Iron Phosphide Nanostructures Produced from a Single-Source Organometallic Precursor: Nanorods, Bundles, Crosses, and Spherulites, Nano Letters 2007, 7, 2920-2925. 19. Gaur R., Jeevanandam P., Effect of anions on the morphology of CdS nanoparticles prepared via thermal decomposition of different cadmium thiourea complexes in a solvent and in the solid state, New Journal of Chemistry 2015, 39, 9442-9453. 20. Khalaji A. D., Preparation and Characterization of NiO Nanoparticles via Solid-State Thermal Decomposition of Ni(II) Complex, J. Clust. Sci. 2013, 24, 189-195. 21. Kim B., Kim J., Baik H., Lee K., Large-scale one pot synthesis of metal oxide nanoparticles by decomposition of metal carbonates or nitrates, Cryst. Eng. Comm. 2015, 17, 4977-4981. 22. Guo L., Arafune H., Teramae N., Synthesis of Mesoporous Metal Oxide by the Thermal Decomposition of Oxalate Precursor, Langmuir. 2013, 29, 4404-4412. 23. Jeragh B., El-Asmy A. A., Spectroscopic and structural study of some 2,5-hexanedione bis(salicyloylhydrazone) complexes: Crystal structures of its Ni(II) and Cu(II) complexes and N-(2,5-dimethyl-1H-pyrrol-1-yl)-2-hydroxy-benzamide,

Spectrochimica

Acta

Part

A:

Molecular and Biomolecular Spectroscopy 2014, 129, 307-313. 24. Jeragh B., El-Asmy A. A., Structure and spectroscopic studies of homo-and heterometallic complexes of adipic acid dihydrazide, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2014, 125, 25-35.


Page 21 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


25. Nemec I., Herchel R., Svoboda I., Boca R., Z. Travnicek, Large and negative magnetic anisotropy in pentacoordinate mononuclear Ni(ii) Schiff base complexes, Dalton Transactions 2015, 44, 9551-9560. 26. Gulino A., Dapporto P., Rossi P., Fragala I., A Novel Self-generating Liquid MOCVD Precursor for Co3O4 Thin Films, Chem. Mater. 2003, 15, 3748-3752. 27. Kumar R. V., Diamant Y., Gedanken A., Sonochemical Synthesis and Characterization of Nanometer-Size Transition Metal Oxides from Metal Acetates, Chem. Mater. 2000, 12, 2301-2305. 28. Peng L., Wang Y., Dong Q., Z. Wang, Passivated ZnSe nanocrystals prepared by hydrothermal methods and their optical properties, Nano-Micro Letters 2010, 2, 190-196. 29. Hou L.-R., Yuan C.-Z., Peng Y., Preparation and photocatalytic property of sunlight-driven photocatalyst Bi38ZnO58, Journal of Molecular Catalysis A: Chemical 2006, 252, 132-135. 30. Reddy R. R., Ahammed Y. N., Gopal K. R. , Raghuram D.V., Optical electronegativity and refractive index of materials, Optical Materials 1998, 10, 95-100. 31. Chang X., Wang T., Zhang P., Zhang J., Li A., J. Gong, Enhanced Surface Reaction Kinetics and Charge Separation of p–n Heterojunction Co3O4/BiVO4 Photoanodes, Journal of the American Chemical Society 2015, 137, 8356-8359. 32. Xu C., Liu Y., Huang B., Li H., Qin X., Zhang X., Dai Y., Preparation, characterization, and photocatalytic properties of silver carbonate, Applied Surface Science 2011, 257, 8732-8736. 33. Tian N., Huang H., He Y., Guo Y., Zhang T., Zhang Y., Mediator-free direct Z-scheme photocatalytic system: BiVO4/g-C3N4 organic-inorganic hybrid photocatalyst with highly efficient visible-light-induced photocatalytic activity, Dalton Transactions 2015, 44, 42974307. 34. Krishnamoorthy K., Kim S., Growth, characterization and electrochemical properties of hierarchical CuO nanostructures for supercapacitor applications, J. Mat. Res. Bull. 2013, 48, 3136-3139. 35. Almar L., Colldeforns B., Yedra L., Estrade S., Peiro F., Morata A., Andreu T., Tarancon A., High-temperature long-term stable ordered mesoporous Ni–CGO as an anode for solid oxidefuel cells, Journal of Materials Chemistry A 2013, 1, 4531-4538. 36. Tong X., Qin Y., Guo X., Moutanabbir O., Ao X., Pippel E., Zhang L., Knez M., Enhanced Catalytic Activity for Methanol Electro-oxidation of Uniformly Dispersed Nickel Oxide Nanoparticles-Carbon Nanotube Hybrid Materials, Small 2012, 8, 3390-3395. 37. Yan Q., Li X., Zhao Q., Chen G., Shape-controlled fabrication of the porous Co3O4 nanoflower clusters for efficient catalytic oxidation of gaseous toluene, J. Hazard. 21 Environment ACS Paragon Plus


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Mater. 2012, 209, 385-391. 38. Huang Y., Zhang Y., Lin S., Yan L., Cao R., Yang R., Liang X., W. Xiang, Sol-gel synthesis of NiO nanoparticles doped sodium borosilicate glass with third-order nonlinear optical properties, Journal of Alloys and Compounds 2016, 686, 564-570. 39. Baghbanian S. M., Synthesis, characterization, and application of Cu2O and NiO nanoparticles supported on natural nanozeolite clinoptilolite as a heterogeneous catalyst for the synthesis of pyrano[3,2-b]pyrans and pyrano[3,2-c]pyridones, RSC Advances 2014, 4, 59397-59404. 40. He Jr. H., Lao C. S., Chen L. J., Davidovic D., Wang Z. L., Large-Scale Ni-Doped ZnO Nanowire Arrays and Electrical and Optical Properties, Journal of the American Chemical Society 2005, 127, 16376-16377. 41. Shao X., Lu W., Zhang R., Pan F., Enhanced photocatalytic activity of TiO2-C hybrid aerogels for methylene blue degradation, Scientific Reports 2013, 3, 1-9. 42. Kim J. G., Pugmire D. L., Battaglia D., Langell M. A., Analysis of the NiCo2O4 spinel surface with Auger and X-ray photoelectron spectroscopy, Applied Surface Science 2000, 165, 70-84. 43. Dong Z., Fu Y., Han Q., Xu Y., Zhang H., Synthesis and Physical Properties of Co3O4 Nanowires, The Journal of Physical Chemistry C 2007, 111, 18475-18478. 44. Xu K., Zou R., Li W., Xue Y., Song G., Liu Q., Liu X., Hu J., Self-assembling hybrid NiO/Co3O4 ultrathin and mesoporous nanosheets into flower-like architectures for pseudocapacitance, Journal of Materials Chemistry A 2013, 1, 9107-9113. 45. Seetawan, U.; Jugsujinda, S.; Seetawan, T.; Euvananont, C.; Junin, C.; Thanachayanont, C.; Chainaronk, P.; Amornkitbamrung, V., Effect of annealing temperature on the crystallography, particle size and thermopower of bulk ZnO. Solid State Sciences 2011, 13, (8), 1599-1603. 46. Zhong J., Li J., Feng F., Lu Y., Zeng J., Hu W., Tang Z., Improved photocatalytic performance of SiO2–TiO2 prepared with the assistance of SDBS, J. Mol. Catal. A: Chem. 2012, 357, 101-105. 47. Zong, J.; Zhu, Y.; Yang, X.; Li, C., Confined growth of CuO, NiO, and Co3O4 nanocrystals in mesoporous silica (MS) spheres. Journal of Alloys and Compounds 2011, 509, (6), 29702975 48. Jegatha Christy A., Umadevi M., Novel combustion method to prepare octahedral NiO nanoparticles and its photocatalytic activity, Materials Research Bulletin 2013, 48, 4248-


Page 22 of 24

Page 23 of 24

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4254. 49. Fan H. M., You G. J., Li Y., Zheng Z., Tan H. R., Shen Z. X., Tang S. H., Feng Y. P., Shapecontrolled synthesis of single-crystalline Fe2O3 hollow nanocrystals and their tunable optical properties, J. Phys. Chem. C. 2009, 113, 9928-9935. 50. Pradhan G. K., Parida K. M., Fabrication, growth mechanism, and characterization of γFe2O3 Nanorods, Appl. Mater. Interface. 2011, 3, 317-323. 51. Banerjee I. A., Yu L.T., Matsui H., Cu nanocrystal growth on peptide nanotubes by biomineralization: Size control of Cu nanocrystals by tuning peptide conformation, PNAS 2003, 100, 14678-14682.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

230x181mm (96 x 96 DPI)

ACS Paragon Plus Environment

Page 24 of 24

Controlled Synthesis of NiO and Co3O4 Nanoparticles from Different

Recommend Documents