Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles

Accepted Manuscript Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles Xiaofei Hu, Hongshun Hao, Weihua Guo, Shanshan Jin, Hong Li, Hongman Hou, Gongliang Zhang, Shuang Yan, Wenyuan Gao, Guishan Liu PII: DOI: Reference:

S0301-0104(16)31030-8 http://dx.doi.org/10.1016/j.chemphys.2017.04.001 CHEMPH 9769

To appear in:

Chemical Physics

Received Date: Accepted Date:

20 December 2016 6 April 2017

Please cite this article as: X. Hu, H. Hao, W. Guo, S. Jin, H. Li, H. Hou, G. Zhang, S. Yan, W. Gao, G. Liu, Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles, Chemical Physics (2017), doi: http://dx.doi.org/10.1016/j.chemphys.2017.04.001

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Hydrothermal synthesis, characterization and enhanced visible-light photocatalytic activity of Co-doped Zn2SnO4 nanoparticles Xiaofei Hu a, Hongshun Hao a,∗, Weihua Guo a, Shanshan Jina, Hong Lia, Hongman Houb,∗, Gongliang Zhangb, Shuang Yana, Wenyuan Gaoa, Guishan Liu a a

Department of Inorganic Nonmetallic Materials Engineering, Dalian Polytechnic

University, Dalian 116034, China b

School of Food Science and Technology, Dalian Polytechnic University, Dalian

116034, China

Corresponding author. Tel: +86 411 86323708, Fax: +86 411 86322020. E-mail address: [email protected] (H.S. Hao), [email protected] (H.M. Hou).

∗

Abstract Various molar concentrations of Co-doped Zn2SnO4 nanoparticles were synthesized by hydrothermal method. The as-prepared samples were characterized by XRD, XPS, FESEM, TEM, UV-Vis and PL. The result of XPS revealed that the Co dopant displayed a chemical state of Co2+ in Zn2SnO4 lattice. UV-Vis results revealed that the absorption edge of samples shifted towards visible light region gradually with the increase of Co doping content. The PL intensity weakened significantly for the Co-doped Zn2SnO4, which indicates that the recombination of photo-generated electrons and holes was suppressed strongly. The photocatalytic activity of Zn2SnO4 was observed by photodegradation of RhB under visible light irradiation. The influences of Co doping content on photocatalytic activity of Zn2SnO4 were investigated. The experiment results indicated that the maximum degradation rate of RhB was 93% in 120min when Co2+ molar concentration was 2mol%. Furthermore, a possible mechanism of photocatalytic degradation of RhB was discussed. Keywords: Co-doped Zn2SnO4 nanoparticles; Hydrothermal method; Photocatalytic activity; Visible light irradiation; Mechanism

1. Introduction As is known, photocatalysis has attracted considerable attentions for their potential applications in solar energy conversion and environment purification [1]. Particularly, photocatalysis is regarded as one of the most effective techniques for restoring the polluted environment. Inverse spinel Zn2SnO4 (ZTO) is a significant ternary oxide n-type semiconductor with high electron mobility, high electrical conductivity and favorable stability. Based on the above advantages, ZTO can be used as gas sensors [2, 3], photoelectrical devices [4], an anode materials for dye sensitized solar cells [5, 6] and lithium-ion battery [7, 8]. Besides, ZTO can effective degrade Benzene [9], Rh6G [10], Methylene blue (MB) [11] and RhB [12] under ultraviolet light (UV) or visible light irradiation. Although the above examples clearly demonstrate the significance of ZTO as a potential candidate for degradation of various pollutants, most of these researches focused on the UV irradiation rather than visible light irradiation. In general, the photocatalytic activity of pure ZTO under visible light irradiation is not desirable due to its wide band gap (Eg=3.6eV [13]) and high recombination rate of electrons and holes. Consequently, it is necessary to adopt some effective ways to extend visible light responsive range and reduce the recombination rate of photo-generated carriers. In recent years, it has been reported that the photocatalytic activity of some semiconductor can be enhanced by metal doping [14-19]. Particularly, doping with transition-metal ions is a widely used method to transform the activities of photocatalysts. It is worth mentioning that doping with transition-metal ions can

greatly influence the electronic structure of host matrix of semiconductor [20]. Among various transition-metals, Co is regarded as an appropriate candidate as dopant. On the one hand, the ionic radius of Co2+ (0.745 Å) is similar to that of Zn2+ (0.74 Å), hence Co2+ can enter into ZTO crystal lattice to substitute Zn2+ easily. On the other hand, Co2+ can serve as carrier trap to restrain the recombination of photo-generated electron-hole pairs, and indirectly enhance the photocatalytic activity of ZTO. As far as we know, although there are numerous literatures about ZTO modification, only few literatures reported Co-doped ZTO. S. Sumithra et al studied the effects of Co on structural, optical and magnetic behavior of ZTO [20]. Bu investigated the effects of Co doping on photocatalytic properties of ZTO thin films [21]. So far, ZTO have been synthesized by numerous techniques, such as thermal evaporation method [22], co-precipitation method [23, 24], sol-gel synthesis [25], and hydrothermal synthesis [26-28]. Among these methods, hydrothermal method permits dopants into crystal lattice of products easily. In our work, Co-doped ZTO nanoparticles were synthesized by a hydrothermal method. The influences of Co doping content on crystalline phase, morphology, UV–Vis absorption spectra, photoluminescence properties and photo-degradation efficiency of RhB dye were investigated. Furthermore, a possible mechanism of ZTO photo-degradation RhB dye under visible light irradiation was proposed. 2. Experimental 2.1. Materials All the reagents used to synthesize ZTO nanoparticles were of analytical grade

without any further purification. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O), Tin chloride pentahydrate (SnCl4·5H2O), Cobalt nitrate hexahydrate (Co(NO3)2·6H2O). 2.2. Synthesis of ZTO nanoparticles In this paper, Co-doped ZTO nanoparticles were synthesized by hydrothermal method. A representative synthesis process was described as follows: appropriate amount of Zn(CH3COO)2·2H2O and certain amount of Co(NO3)2·6H2O were dissolved in 30mL deionized water to form well-distributed solution. Then, 4mmol of SnCl4·5H2O was also dissolved into 30mL deionized water to form a transparent solution. Next, SnCl4·5H2O solution was dropwise added into the well-distributed solution under continuous stirring to compose mixture solution. Acting as a mineralizer, NaOH aqueous solution (2M) was dropwise added into the mixture solution till pH=9. After magnetic stirring of 30 minutes, the obtained slurry was transferred to a Teflon-lined stainless steel autoclave (100mL capacity) and heated at 200°C for 24h. After the hydrothermal reaction, the autoclave was cooled to room temperature naturally. The precipitate was collected by a centrifugation method and washed by distilled water and absolute alcohol for several times. Finally, the products were dried at 80°C for 10 h and the Zn2-xCoxSnO4 (x=0, 0.005, 0.01, 0.02, 0.03, 0.05) powders were obtained. Pure ZTO powders were synthesized by the same method without Co(NO3)2·6H2O. For convenience, ZTO powders doping with 0.0mol%, 0.5mol%, 1mol%, 2mol%, 3mol% and 5mol% Co2+ ions were labeled as P0, P1, P2, P3, P4 and P5 in sequence.

2.3. Characterization The crystallinity and phase composition of as-prepared samples were investigated by X-ray diffraction analysis (XRD-7000, SHIMADZU) with Cu Kα radiation in the range of 10°-70° (2θ). The elemental composition and chemical state were investigated by energy dispersive spectrometry (EDS, X-Max50) and X-ray photoelectron

spectroscopy

(XPS, Thermo ESCALAB 250),

respectively.

The

morphology, particle size and crystalline structure of as-prepared samples were characterized by field emission scanning electron microscope (FE-SEM, JSM-7800F) and transmission electron microscopy (TEM, JEOLJEM-2100). The UV-Vis diffuse reflectance spectra of all samples were recorded by an UV-Vis spectrophotometer (UV-Vis, Lambda35). Photoluminescence (PL) spectra were measured by Hitachi F7000 fluorescence spectrophotometer at the excitation wavelength of 260 nm. 2.4. Photodegradation of RhB under visible light irradiation The photocatalytic activities of all prepared samples were evaluated by the degradation of RhB in an aqueous solution under a visible light irradiation (A 125 W mercury lamp was used as a light source to trigger the photocatalytic reaction). For the effective degradation of RhB, 100 mg of as-prepared catalyst was dispersed in 100 mL aqueous solution of RhB (10-5molL-1) under continuous stirring. Ahead of irradiation, the suspension was stirred for 30min in dark condition to reach the absorption-desorption equilibrium between RhB solution and photocatalyst. Next, the suspension was exposed to visible light irradiation with continuous stirring. Finally, about 5 mL of the suspensions were sampled and centrifuged every 20 min. The

degradation efficiencies of RhB were recorded by monitoring the variations of absorbance

at

the

maximum

absorption

wavelength

using

a

UV-Vis

spectrophotometer (UV-Vis, Lambda35). 3. Results and discussion 3.1. Structural and phase analysis The XRD patterns of pure and ZTO with different Co doping content were shown in Fig.1(a). Nine significantly diffraction peaks which corresponding to (111), (220), (311), (222), (400), (331), (422), (511) and (440) planes are observed. It can be found that the positions and relative intensities of diffraction peak of all samples match well with the standard ZTO data (JCPDS file No. 24-1470). Neither diffraction peaks related to Co oxide nor impurities are detected in the XRD patterns, which can be ascribed to low ion doping content. A detailed comparison of XRD patterns of pure and Co-doped ZTO powders (Fig.1(b)) exhibits tiny shifts of peak position toward lower 2θ angles, suggesting the variation in the unit cell volume caused by the possible substitution of Zn by Co. A possible lattice substitution of Zn2+ by Co 2+ relying on a slight increase in cell volume since the ionic radii of Co 2+ (0.745 Å) is more than that of Zn2+ (0.74 Å). In other words, the dopant of Co leads to the lattice expansion in a certain degree. Furthermore, the elemental composition analysis was investigated by EDS. The EDS patterns of Co-doped ZTO in Fig.1(c) further demonstrate that the as-prepared nanoparticles are composed of Sn, Zn, O and Co. Crystalline sizes can be calculated by Scherrer equation [29] applied to the most significant peaks relevant to the (311) plane. In principle, Scherrer equation is

described as: D = (kλ)/(βcosθ), where D is the average crystallite size, k is Scherrer constant which generally takes a value about 0.89, λ is the X-ray wavelength (0.15406 nm), θ is the Bragg diffraction angle and β is the full width at the half maximum (FWHM) of the diffraction peak, respectively. The values of crystalline size, the lattice constants, unit cell volume and density of Zn2-xCo xSnO4 powders were listed in Table1. As can be seen from Table 1, the crystallite sizes of Co-doped ZTO are slightly lower than that of pure, which indicates that the dopants cause a slight lattice distortion in the spinel structure. 3.2. XPS analysis In order to investigate the chemical state of element and chemical composition of Co in the as-synthesized ZTO sample, X-ray photoelectron spectroscopy (XPS) measurements were implemented. The survey scan of XPS spectra of 2mol% Codoped ZTO is shown in Fig.2(a), it is clear that the peaks of Zn, Sn, O, and Co, together with C can be observed. The XPS spectra of Zn is displayed in Fig.2(b), the spectra of Zn 2p centered at around 1042.98 eV and 1019.88 eV can be attributed to the spin orbit split peaks of Zn 2p1/2 and Zn 2p3/2 respectively. These values are in good agreement with values of Zn2+ [30]. Fig.2(c) presents the XPS spectra of Sn, a couple of well-defined peaks centered at around 492.88 eV and 484.58 eV originating due to the spin orbit coupling of 3d electrons corresponding to the binding energies of Sn 3d3/2 and Sn 3d 5/2 respectively, which are characteristic of Sn4+ cations [31]. As is shown in Fig.2(e), the spectra of Co 2p centered at 793.98 eV and 779.28 eV belong to the binding energy of Co 2p1/2 and Co 2p3/2 respectively [32], which suggests that

dopant of Co in ZTO lattice displays a chemical state of Co2+. In addition, the peak centered at 528.48eV can be assigned to the binding energy of O 1s of ZTO (Fig.2(d)). Thus, the XPS analysis further demonstrates the Co-doped ZTO was successfully synthesized. 3.3. Morphology analysis The size and detailed morphological characterization of Co-doped ZTO nanoparticles were investigated by field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM). As is shown in Fig.3, the pure and Co-doped ZTO samples are composed of a large number of spherical-like nanoparticles with rough surface. Also, these nanoparticles grew together densely and slightly agglomeration. Additionally, it can be found that doping almost no caused structural change, which is in accordance with the results of XRD. Fig.4(a-c) describe the TEM images of 2mol% Co-doped ZTO, which is formed by a number of pseudospherical nanoparticles with sizes in the range of 50-70nm. Furthermore, these nanoparticles have attached small irregular nanoparticles with sizes below 4 nm. The bimodal distribution is coincident with dissolution-recrystallization mechanisms and growth through an Ostwald ripening process, which occurs during the hydroxide precursor transformation in the hydrothermal treatment [33]. As is shown in Fig.4(d), the lattice fringes are obvious with a spacing of 0.5nm, which correspond to the spacing of (111) crystal planes of ZTO. The corresponding SAED pattern is composed by a set of concentric circles (inset of Fig.4(d)), which suggests a polycrystalline feature of the ZTO nanoparticles. 3.4. UV-Vis diffuse reflectance spectroscopy Diffuse reflectance spectroscopy is an available tool to reveal the optical properties and energy structures of semiconductor nanostructure [13]. The optical

absorption spectra of all ZTO samples were detected by UV-vis DRS. It can be seen from Fig.5(a) that all samples have a steep absorption edge, indicating that the light absorption was not due to the transition from the impurity level but was owing to the band gap transition [34]. What’s more, the absorption edge of samples was gradually shifted towards the visible light region with the increasing of Co doping content, which can be attributed to the interaction of Co ions with ZTO lattice. The band-gap values can be calculated according to the equation of Eg =1240/λ [35], and (αhν)1/2 versus (hν) curves graph of all samples were exhibited in Fig.5(b). The band-gap values of all samples are listed in Table.1. As illustrated in Fig.5(b), with the increase of Co doping content, the band gap value decreased, which demonstrates that Co doping can reduce the band-gap energy of ZTO, therefore extend the response range of the visible light. In summary, the enhancement of visible light absorption may be attributed to the formation of Co+/ Co3+ doping energy level in the band gap of ZTO and the d-d transition of Co2+ (2T2g → 2A2g, 2T1g) [36]. 3.5. Photoluminescence analysis The Photoluminescence (PL) spectra have been widely used to investigate the recombination rate of photo-generated electron-hole pairs in semiconductor [37]. The room temperature PL spectra of all samples were measured at an excitation wavelength of 260 nm. As shown in Fig.6, emission peaks centered at 360, 373, 390, 407, 423, 450, 468nm have been found. It has been investigated that the emission peak centered at 360 nm is probably attributed to the band to band transition of the recombination of photo-generated electrons and holes [37]. Besides, two emission peaks centered at 410 nm and 472 nm can be ascribed either to oxygen vacancies or to other types of defects, such as O2 interstitials and tin vacancies [38]. Although the peak positions of Co-doped ZTO are in agreement with pure ZTO, the peak intensities

are quite sensitive to Co doping content. The emission peaks of pure ZTO have the highest relative intensity, indicating the photo-generated electron-hole pairs have a high recombination rate. However, after the doping of Co 2+, the peak intensities weakens significantly, which suggests that the recombination of photo-generated electron-hole pair is suppressed strongly [39]. The suppression effect is enhanced with the increase of Co doping content, which is due to the dopants can act as capture traps of photo-induced electron-hole pairs, and consequently improve the effective separation of charge carriers [18]. 3.6. Photocatalytic activity and a possible mechanism of photocatalytic reaction To confirm the reliability under visible light driven photocatalytic behavior of all photocatalysts, a series of photocatalytic degradation experiments were implemented. Generally speaking, RhB is extremely stable under visible light irradiation in the absence of photocatalysts, so it is applied to the model of pollutants. The photocatalytic activity of as-prepared photocatalysts was carried out by degradation of RhB aqueous solution under visible light irradiation. The timedependent absorption spectra of RhB aqueous solution in the presence of P3 sample was shown in Fig.7(a). It can be seen that the intensity of characteristic adsorption peak of RhB around 554 nm continues to reduce accompanying with a gradual blue shift with the increase of irradiation time. The blue shift can be attributed to stepwise deethylation of RhB solution [12]. The photocatalytic activity of ZTO with different Co doping content was shown in Fig.7(b). The degradation rate of RhB was only about 72% in existence of pure ZTO after being irradiated for 120 min under visible light. The comparison of photocatalytic degradation efficiency of ZTO

with different Co doping content has been exhibited in Fig.7(c). It can be conclude that Co-doped ZTO photocatalyst exhibited better photocatalytic activity than that of pure. In addition, the degradation can be ignorable in the absence of photocatalyst, indicating the degradation of RhB should be regarded as the photodegradation effect of ZTO. It is worth mentioning that the optimal Co doping content was found to be 2mol% Co2+ doping (the degradation rate reached 93% in 120 min). In summary, the enhanced photocatalytic activity can be explained as follows: (a) ZTO doped with 2mol% Co 2+ has a larger range of visible light response, which can generate more electrons and holes to enhance the photocatalytic activity; (b) the doping of Co reduced the PL intensity greatly, indicating the recombination of photo-generated electrons and holes was inhibited strongly, which is favorable to the photo-degradation activity. Moreover, the photocatalytic degradation of RhB followed pseudo-first order kinetics and the rate constant should be determined by the following equation: ln(C/C0) = -kt [40]. Where C0 is initial concentration of RhB, C is the concentration at time t and k is the reaction rate constant. The plots of ln (C/C0) versus time t are illustrated in Fig.7(d). Kinetic apparent rate constants k are given by the slopes of linear and estimated to be 0.0089, 0.0091, 0.0127, 0.0180, 0.0123 and 0.0081min-1 for P0, P1, P2, P3, P4 and P5, respectively. However, the rate constant k calculated in the absence of photocatalyst is merely 0.0012 min-1. The obtained results demonstrate that ZTO doped with 2mol% Co2+ is a promising photocatalyst for the degradation of RhB. Moreover, in order to investigate the photocatalytic stability,

the recycled experiments of ZTO catalyst doped with 2mol% Co2+ were operated under visible light illumination, the results were exhibited in Fig.7(e). The results indicated that the recycled usage did not affect the ZTO photocatalytic activity greatly even after four runs, which suggested that ZTO doped with 2mol% Co2+can be used as a recyclable catalyst. On the basis of a previous research [41], the degradation process of RhB under visible light irradiation occurred by two competitive process: a photocatalytic process and a photosensitized process. The schematic diagram of visible light driven photocatalytic reaction happened on the surface of Co-doped ZTO nanoparticles has been illustrated in Fig.8. When visible light irradiated the surface of Co-doped ZTO, photo-generated electrons and holes are generated due to the existence of defects and localized surface states [42]. Then, holes are captured by H2O molecules or OH- ions to produce hydroxyl radicals(·OH). At the same time, electrons are captured by O2 molecules to generate oxygen radicals (O2·-) [43, 44]. In addition, the doped Co2+ ions can act as a capture trap of electrons and holes, resulting in the formation of Co+ and Co3+ ions. So, the doped Co2+ ions can reduce the recombination of electrons and holes, which is in accordance with the result of decrease of PL intensity. Besides, the trapped charges can be released to regenerate Co2+ ions easily. The process also leads to the formation of O2·- and ·OH. However, Co2+ may serve as the recombination centers of charge carriers once the Co2+ content is excess, which may reduce the photocatalytic activity of catalyst. This point can be demonstrated by the photocatalytic result of P4 and P5 samples.

Finally, the high oxidizing O2·- and·OH can further oxidize the RhB molecules until their complete decomposition [18]. The relevant reaction equations are shown as follows: ZTO + hν → e- + h+

(1)

h+ + OH-/H2O →·OH e- + O2 → O2·-

(2) (3)

Co2+ + e- → Co +

(4)

Co2+ + h+ → Co3+

(5)

Co+ + O2→ Co2+ + O2·-

(6)

Co3+ + OH- → Co2+ + ·OH

(7)

Co2+ + e- → Co +

(8)

Co+ + h+ → Co2+

(9)

RhB + ·OH/O2·-→ RhB (intermediates) → finally products

(10)

The photosensitized process of RhB takes place through the reaction of O2·/O2 and the radical RhB·+. The related reaction equations are described as follows [45]. RhB + hν → RhB* RhB* + ZTO →RhB·++ ZTO (e-) ZTO (e-) + O2 →O2·RhB⋅+ + O2/O2·-→ decomposition products

(11) (12) (13) (14)

4. Conclusion In this study, pure and Co-doped ZTO nanoparticles have been successfully synthesized by a facile hydrothermal method employing NaOH as a mineralizer. The

as-prepared samples are composed of numerous pseudo-spherical nanoparticles with the size ranging from 50 to 70 nm. The maximum degradation rate of RhB was 93% in 120min when Co doping content was 2mol%. The enhanced photocatalytic activity can be explained two points. On the one hand, ZTO doped with 2mol% Co2+ has a larger range of visible light response, which can generate more electrons and holes to enhance the photocatalytic activity. On the other hand, the doping of Co reduced the PL intensity greatly, indicating the recombination of photo-generated electrons and holes was inhibited strongly, which is favorable to the photo-degradation activity. This work demonstrates that ZTO doped with 2mol% Co 2+ has a potential application in photocatalytic degradation toward RhB dye.

Acknowledgements This work was partially supported by Open Research Fund Project of National Engineering Research Center of Seafood (No. 2012FU125X03), S & T Program of Liaoning Provincial Education Department (No. 2016J021), and Key Science and Technology Platform of Liaoning Provincial Education Department (No. 2011-191).

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Figures

Fig.1. (a) XRD patterns and (b) enlarged patterns for selected 2θ ranges of P0, P1, P2, P3, P4 and P5 with Co2+ of 0.0mol%, 0.5mol%, 1mol%, 2mol%, 3mol% and 5mol% in sequence. (c) EDS spectrum of ZTO with 2mol% Co2+.

Fig.2. (a) Survey, (b) Zn 2p, (c) Sn 3d, (d) O 1s and (e) Co 2p XPS spectra of asprepared 2mol% Co-doped ZTO nanoparticles.

Fig.3. FESEM images of (a) pure ZTO and (b) ZTO with 2mol% Co2+

Fig.4. (a-c) TEM images at different magnification and (d) HRTEM images of 2mol% Co-doped ZTO nanoparticles (Inset: the corresponding SAED pattern).

Fig.5. (a) UV–Vis absorption spectra; (b) (αhν)1/2 versus (hν) curves graph of all samples. (P0, P1, P2, P3, P4 and P5 represent the sample of Co2+ with 0.0mol%, 0.5mol%, 1mol%, 2mol%, 3mol% and 5mol%, respectively).

Fig.6. The room temperature PL spectra of P0, P1, P2, P3, P4 and P5 with Co2+ of 0.0mol%, 0.5mol%, 1mol%, 2mol%, 3mol% and 5mol%, respectively.

Fig.7. (a) Time-dependent absorption spectra of RhB solution in the presence of P3 sample; (b) Temporal course of photocatalytic degradation of RhB aqueous solution; (c) The photocatalytic degradation efficiency of all samples; (d) The plots of ln(C/C0) versus time t of all samples; (e) Cycling test of P3 sample for the degradation of RhB aqueous. (P0, P1, P2, P3, P4 and P5 represent the sample of Co2+ with 0.0mol%, 0.5mol%, 1mol%, 2mol%, 3mol% and 5mol%, respectively).

Fig.8. (a) Simple procedure chart of degradation process of RhB under visible light irradiation; (b) Schematic diagram of visible light driven photocatalytic reaction.

Table1. The structural refinement result of Zn2-xCo xSnO4 and band gap value Zn2-xCo xSnO4

Latticeconstanta

Volumea

Densitya

Crystalline size a

Band gapb

X (mol%)

a=b=c (Å)

(Å3)

(g/cm3)

(nm)

(eV)

0

8.65725±0.00099

648.84

6.4174

16.709

3.45

0.5

8.65923±0.001862

649.29

6.4131

16.185

3.3

1

8.66169±0.000965

649.84

6.4076

16.151

3.22

2

8.65987±0.002933

649.43

6.4116

15.719

3.08

3

8.65735±0.001992

648.87

6.4172

15.720

2.9

5

8.6586±0.001504

649.15

6.4144

16.575

2.8

a

Calculated according to the XRD data.

b

Calculated according to the UV–Vis DRS results.

The schematic diagram of visible light driven photocatalytic reaction happened on the surface of Co-doped ZTO nanoparticles.

Highlights 1. Co-doped Zn2SnO4 nanoparticles were synthesized by a hydrothermal method. 2. The effect of Co doping content on photocatalytic activity of Zn2SnO4 were investigated. 3. The maximum degradation rate of RhB was 93% when Co doping content was 2mol%. 4. A possible mechanism of photocatalytic degradation of RhB was proposed.