Hydrothermal derived nitrogen doped SrTiO3 for efficient visible light driven photocatalytic reduction of chromium(VI)
© The Author(s) 2016
Received: 19 May 2016
Accepted: 11 July 2016
Published: 19 July 2016
In this work, we report on the synthesis of nitrogen doped SrTiO3 nanoparticles with efficient visible light driven photocatalytic activity toward Cr(VI) by the solvothermal method. The samples are carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy and photocatalytic test. It is found that nitrogen doping in SrTiO3 lattice led to an apparent lattice expansion, particle size reduction as well as subsequent increase of Brunner–Emmet–Teller surface area. The visible light absorption edge and intensity can be modulated by nitrogen doping content, which absorption edge extends to about 600 nm. Moreover, nitrogen doping can not only modulate the visible light absorption feature, but also have consequence on the enhancement of charge separation efficiency, which can promote the photocatalytic activity. With well controlled particle size, Brunner–Emmet–Teller surface area, and electronic structure via nitrogen doping, the photocatalytic performance toward Cr(VI) reduction of nitrogen doped SrTiO3 was optimized at initial hexamethylenetetramine content of 2.
Hexavalent chromium (Cr(VI)) is a common pollutant detected in groundwater originated from excessively released of electroplating, pigment production and tanning of leather, etc. (Wang et al. 2013a). Cr(VI) has raised considerable attention because of its high toxic, intense mobility and strong teratogenic activity to human organisms. The World Health Organization (WHO) has stipulated that Cr(VI) concentration in drinking water should be below 0.05 ppm (Chen et al. 2011). Precipitation (Gheju and Balcu 2011), adsorption (Sun et al. 2014a, b), ion exchange (Edebali and Pehlivan 2010) and membrane separation (Hsu et al. 2013) as conventional techniques are commonly used to eliminate Cr(VI) from wastewater. Precipitation and adsorption processes are economic and effective, but only efficient when the Cr(VI) concentration is relatively high (Abyaneh and Fazaelipoor 2016; Hokkanen et al. 2016). Ion exchange is high-efficiency in general, but it is rather expensive to maintain and operate (Ali et al. 2015). Some even cause secondary pollution. For example, solvent extraction method could bring in organic pollutants, sulfide precipitator as common precipitator may be residual and generate hydrogen sulfide (H2S). In general, conventional techniques are either low efficiency or cost too much when they are applied to low Cr(VI) concentration in wastewater (Wang et al. 2012a; Huang and Huang 1996).
Semiconductor photocatalytic reduction technology has attracted a lot of attention in recent years (Miseki et al. 2008; Kato and Kudo 2002; Wang et al. 2009; Mu et al. 2011; Nakhjavan et al. 2012; Duo et al. 2015; Zhang et al. 2009). Semiconductor photocatalytic technology has a promising prospect for wastewater Cr(VI) removing because it is efficiency and inexpensive to maintain and operate without secondary pollution (Hu et al. 2014; Meichtry et al. 2014; Gherbi et al. 2013; Alanis et al. 2013). Strontium titanate (SrTiO3) could be applied in Cr(VI) ion contaminant reduction with excellent photocatalyst performance, but it is only effective under ultraviolet irradiation which is about 4 % of the sunlight (Zheng et al. 2011). That is to say, strontium titanate is ineffective under visible light irradiation when applied to photocatalysis because it has a 3.2 eV band gap energy (Dong et al. 2012). Many leading groups also take advantage of the high bandgap. Li Ji group and Ib Chorkendorff group use SrTiO3 and TiO2 as protective window layers for Si photocathode during water splitting, and they achieve good result (Ji et al. 2015; Bae et al. 2016). Doping with nonmetal atoms to SrTiO3 material could hoist the valence band edge and extend its optical absorption edge towards the visible light range, resulting in visible light driven photocatalytic activity (Sulaeman et al. 2011; Zou et al. 2012). The perovskite phases materials characteristics depend on the anionic composition to a large extent. Therefore, replacing oxygen with other anions, take nitrogen for example, can greatly influence the physicochemical property of the material. There are many reports about doping action including anionic dopant species and metals ions, and anionic doping could narrow the desired semiconductor band gap better than cation ions doping (Khan et al. 2002; Chen and Burda 2008).
In our work, nitrogen-doped SrTiO3 powders are synthesized by hydrothermal method reaction. We take hexamethylenetetramine as doping sources and KOH as mineralizer to obtain the fine particles with excellent photocatalytic activity. The nitrogen doping effects on SrTiO3 nanoparticles are fully studied in an attempt to investigate the microstructure, optical properties and the relevance to the improved photocatalytic activity toward chromium(VI) reduction.
Synthesis of nitrogen doped SrTiO3 samples
Titanium tetraisopropoxide Ti(OC3H7)4 and strontium nitrate Sr(NO3)2·4H2O were used as starting materials, hexamethylenetetramine (HMT) as nitrogen source, and KOH as mineralizer. All of them were reagent grade and used without further purification. SrTiO3 was prepared by hydrothermal method. Ti(OC3H7)4 was dissolved in 10 mL 2-propanol firstly, Sr(NO3)2 aqueous solution was added to Ti(OC3H7)4 propanol solution dropwise with continuously stirring. Then, 0–8 g of HMT and 20 mL of 2 M KOH aqueous solution were added to the suspension in turn. The solution was placed into a Teflon container with a stainless steel autoclave outside and then the solution was heated at 200 °C for 3 h in an oven. After that, the autoclave was cooled to room temperature naturally, the obtained powder was washed with distilled water and alcohol three times and dried in vacuum at 60 °C overnight (Sulaeman et al. 2010). The final samples were labeled as pure SrTiO3, N-SrTiO3(0.5), N-SrTiO3(1), N-SrTiO3(2), N-SrTiO3(3), N-SrTiO3(4), N-SrTiO3(5), N-SrTiO3(6) and N-SrTiO3(8) with the increased HMT content.
X-ray power diffraction (XRD) was applied to characterize the purity and crystallinity of all our samples (D8 Advance Bruker X-ray diffractometer, CuKα radiation, 2θ = 20–80o). Transmission electron microscopy (TEM) was used to determine the morphology of the as-prepared samples (JEM-2010 apparatus, 200 kVA acceleration voltage). Diffusive reflectance UV–Vis spectrophotometer (Perkin-Elmer Lambda35) was employed to measure the samples UV–Vis absorption, BaSO4 was taken as the reference sample. Barrett–Emmett–Teller (BET) technique was taken to determine the specific surface areas (Micromeritics ASAP 2000 Surface Area and Porosity Analyzer). X-ray photo spectrometer (XPS) analysis was employed for sample element state (ESCALab220i-XL). PGSTAT302 N potentiostat galvanostat Autolab electrochemical working station using a standard three-compartment cell was used for photoelectrochemical characteristics under 300 W Xe arc lamp (≥420 nm). The fluorine-doped tin oxide (FTO) glasses (0.6 cm2) were washed for 30 min using absolute ethanol with ultrasonication. 0.1 g sample mixed with 0.01 g Polyvinylidene fluoride (PVDF) and 0.5 mL N-methyl pyrrolidinone (NMP) were placed in an glass bottle under magnetic stirring for at least 8 h. Then the obtained mixtures were coated on the FTO glasses. Photocatalyst solution was coated onto the FTO glasses substrate by drop casting using 5 μL pipette tip, and 3 drops were enough. Then we use the pipette tip to smooth the film at room temperature in the air. Lastly, the coated FTO glasses were dried for 4 h at 60 °C in the air. Photocatalyst coated FTO glass, a piece of Pt sheet, an Ag/AgCl electrode and 0.5 M sodium sulfate were used as the working electrode, counter electrode, reference electrode and electrolyte, respectively.
Photocatalytic reactivity test
Results and discussion
In summary, nitrogen doped SrTiO3 nanoparticles with controlled particle size, electronic structure and efficient visible light driven photocatalytic activity toward Cr(VI) were successfully prepared by a solvothermal method. XRD, BET and TEM analyses indicated that nitrogen doped SrTiO3 nanoparticles with cube-like morphology exhibited an apparent lattice expansion, particle size reduction as well as subsequent increase of BET surface area via nitrogen doping. The visible light absorption edge and intensity can be modulated by nitrogen doping content, which absorption edge extends to about 600 nm. Moreover, nitrogen doping can not only modulate the visible light absorption feature, but also have consequence on the enhancement of charge separation efficiency, which can promote the photocatalytic activity. With well controlled particle size, BET surface area, and electronic structure via nitrogen doping, the visible light driven photocatalytic performance toward Cr(VI) reduction of nitrogen doped SrTiO3 was optimized at initial HMT content of 2. Such a finding may help to provide hints for developing and designing new photocatalytic semiconductors.
The manuscript was conceived and designed by SYG and XGJ. ZLX and ST performed acquisition of data. WXJ made some revisions of the manuscript. All authors read and approved the final manuscript.
This work is financially supported by the National Natural Science Foundation of China (Grants 21267041, 21367018, 21563021), the Project of Scientific and Technological Innovation Team of Inner Mongolia University (12110614).
The authors declare that they have no competing interests.
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- Abyaneh AS, Fazaelipoor MH (2016) Evaluation of rhamnolipid (RL) as a biosurfactant for the removal of chromium from aqueous solutions by precipitate flotation. J Environ Manage 165:184–187View ArticleGoogle Scholar
- Alanis C, Natividad R, Barrera-Diaz C, Martínez-Miranda V, Prince J, Valente JS (2013) Photocatalytically enhanced Cr(VI) removal by mixed oxides derived from MeAl (Me: Mg and/or Zn) layered double hydroxides. Appl Catal B Environ 140–141:546–551View ArticleGoogle Scholar
- Ali SW, Mirza ML, Bhatti TM (2015) Removal of Cr(VI) using iron nanoparticles supported on porous cation-exchange resin. Hydrometallurgy 157:82–89View ArticleGoogle Scholar
- Bae D, Shayestehaminzadeh S, Thorsteinsson EB, Pedersen T, Hansen O, Seger B, Vesborg PCK, Ólafsson S, Chorkendorff I (2016) Protection of Si photocathode using TiO2 deposited by high power impulse magnetron sputtering for H2 evolution in alkaline media. Sol Energy Mater Sol Cells 144:758–765View ArticleGoogle Scholar
- Chen XB, Burda C (2008) The electronic origin of the visible-light absorption properties of C-, N-and S-Doped TiO2 nanomaterials. J Am Chem Soc 130:5018–5019View ArticleGoogle Scholar
- Chen H, Shao Y, Xu ZY, Wan HQ, Wan YQ, Zheng SR, Zhu DQ (2011) Effective catalytic reduction of Cr(VI) over TiO2 nanotube supported Pd catalysts. Appl Catal B Envrion 105:255–262View ArticleGoogle Scholar
- Dong WJ, Li XY, Yu J, Guo WC, Li BJ, Tan L, Li CR, Shi JJ, Wang G (2012) Porous SrTiO3 spheres with enhanced photocatalytic performance. Mater Lett 67:131–134View ArticleGoogle Scholar
- Dong HJ, Sun JX, Chen G, Li CM, Hua YD, Lv CD (2014) An advanced Ag-based photocatalyst Ag2Ta4O11 with outstanding activity, durability and universality for removing organic dyes. Phys Chem Chem Phys 16:23915–23921View ArticleGoogle Scholar
- Duo F, Wang Y, Mao X, Zhang X, Wang Y, Fan C (2015) A BiPO4/BiOCl heterojunction photocatalyst with enhancedelectron-hole separation and excellent photocatalytic performance. Appl Surf Sci 340:35–42View ArticleGoogle Scholar
- Edebali S, Pehlivan E (2010) Evaluation of Amberlite IRA96 and Dowex 1 × 8 ion-exchange resins for the removal of Cr(VI) from aqueous solution. Chem Eng J 161:161–166View ArticleGoogle Scholar
- Gheju M, Balcu I (2011) Removal of chromium from Cr(VI) polluted wastewaters by reduction with scrap iron and subsequent precipitation of resulted cations. J Hazard Mater 196:131–138View ArticleGoogle Scholar
- Gherbi R, Trari M, Nasrallah N (2013) Influence of light flux and hydrodynamic flow regime on the photoreduction of Cr(VI) on the CuAl2O4/TiO2 hetero-junction. Chem Eng 1:1275–1282Google Scholar
- Hokkanen S, Bhatnagar A, Repo E, Lou S, Sillanpää M (2016) Calcium hydroxyapatite microfibrillated cellulose composite as a potential adsorbent for the removal of Cr(VI) from aqueous solution. Chem Eng J 283:445–452View ArticleGoogle Scholar
- Hsu HT, Chen SS, Tang YF, Hsi HC (2013) Enhanced photocatalytic activity of chromium(VI) reduction and EDTA oxidization by photoelectrocatalysis combining cationic exchange membrane processes. J Hazard Mater 248–249:97–106View ArticleGoogle Scholar
- Hu XF, Ji HH, Chang F, Luo YM (2014) Simultaneous photocatalytic Cr(VI) reduction and 2,4,6-TCP oxidation over g-C3N4 under visible light irradiation. Catal Today 224:34–40View ArticleGoogle Scholar
- Huang C, Huang CP (1996) Application of aspergillus oryzae and rhzopus oryzae for Cu(II) removal. Water Res 30:1985–1990View ArticleGoogle Scholar
- Ji L, McDaniel MD, Wang SJ, Posadas AB, Li XH, Huang HY, Lee JC, Demkov AA, Bard AJ, Ekerdt JG, Yu ET (2015) A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst. Nat Nanotechnol 10:84–90View ArticleGoogle Scholar
- Kato H, Kudo A (2002) Visible-light-response and photocatalytic activities of TiO2 and SrTiO3 photocatalysts codoped with antimony and chromium. J Phys Chem B 106:5029–5034View ArticleGoogle Scholar
- Khan SUM, Al-Shahry M, Ingler WB Jr (2002) Efficient photochemical water splitting by a chemically modified n-TiO2. Science 297:2243–2246View ArticleGoogle Scholar
- Kumar S, Tonda S, Baruah A, Kumar B, Shanker V (2014) Synthesis of novel and stable g-C3N4/N-doped SrTiO3 hybrid nanocomposites with improved photocurrent and photocatalytic activity under visible light irradiation. Dalton Trans 43:16105–16114View ArticleGoogle Scholar
- Larson AC, Von Dreele RB (1994) General structure analysis system (GSAS). Los Alamos National Laboratory Report LAUR, pp 86–748Google Scholar
- Ma YL, Liu XQ, Li Y, Su YG, Chai ZL, Wang XJ (2014) K4Nb6O17·4.5H2O: a novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III). J Hazard Mater 279:537–545View ArticleGoogle Scholar
- Meichtry JM, Colbeau-Justin C, Custo G, Litter MI (2014) Preservation of the photocatalytic activity of TiO2 by EDTA in thereductive transformation of Cr(VI). Studies by time resolved microwave conductivity. Catal Today 224:236–243View ArticleGoogle Scholar
- Mikhailovskaya ZA, Buyanova ES, Petrova SA, Morozova MV, Zhukovskiy VM, Zakharov RG, Tarakina NV, Berger IF (2013) Cobalt-doped Bi26Mo10O69: crystal structure and conductivity. J Solid State Chem 204:9–15View ArticleGoogle Scholar
- Miseki Y, Kato H, Kudo A (2008) Water splitting into H2 and O2 over niobate and titanate photocatalysts with (111) plane-type layered perovskite structure. Energy Environ Sci 2:306–314View ArticleGoogle Scholar
- Mu RX, Xu ZY, Li LY, Shao Y, Wan HQ, Zheng SR (2010) On the photocatalytic properties of elongated TiO2 nanoparticles for phenol degradation and Cr(VI) reduction. J Hazard Mater 176:495–502View ArticleGoogle Scholar
- Mu S, Long Y, Kang SZ, Mu J (2011) Surface modification of TiO2 nanoparticles with a C60 derivative and enhanced photocatalytic activity for the reduction of aqueous Cr(VI) ions. Catal Commun 11:741–744View ArticleGoogle Scholar
- Nakhjavan B, Tahir MN, Natalio F, Panthofer M, Gao H (2012) Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions. Nanoscale 4:4571–4577View ArticleGoogle Scholar
- Ruzimuradov O, Sharipov K, Yarbekov A, Saidov K, Hojamberdiev M, Prasad RM, Cherkashinin G, Riedel R (2015) A facile preparation of dual-phase nitrogen-doped TiO2-SrTiO3 macroporous monolithic photocatalyst for organic dye photo degradation under visible light. J Eur Ceram Soc 35(6):1815–1821View ArticleGoogle Scholar
- Su YG, Huang SS, Wang TT, Peng LM, Wang XJ (2015) Defect-mediated efficient catalytic activity toward p-nitrophenol reduction: a case study of nitrogen doped calcium niobate system. J Hazard Mater 295:119–126View ArticleGoogle Scholar
- Sulaeman U, Yin S, Sato T (2010) Solvothermal synthesis and photocatalytic properties of nitrogen-doped SrTiO3 Nanoparticles. J NanomaterGoogle Scholar
- Sulaeman U, Yin S, Sato T (2011) Visible light photocatalytic activity induced by the carboxyl group chemically bonded on the surface of SrTiO3. Appl Catal B Environ 102:286–290View ArticleGoogle Scholar
- Sun XT, Yang LR, Li Q, Zhao JM, Li XP, Wang XQ, Liu HZ (2014a) Amino-functionalized magnetic cellulose nanocomposite as adsorbent for removal of Cr(VI): synthesis and adsorption studies. Chem Eng J 241:175–183View ArticleGoogle Scholar
- Sun YY, Yue QY, Mao YP, Gao BY, Gao Y, Huang LH (2014b) Enhanced adsorption of chromium onto activated carbon by microwave-assisted H3PO4 mixed with Fe/Al/Mn activation. J Hazard Mater 265:191–200View ArticleGoogle Scholar
- Sun Q, Li H, Zheng SL, Sun ZM (2014c) Characterizations of nano-TiO2/diatomite composites and theirphotocatalytic reduction of aqueous Cr(VI). Appl Surf Sci 311:369–376View ArticleGoogle Scholar
- Wang DF, Kako T, Ye JH (2009) New Series of Solid-Solution Semiconductors (AgNbO3)1-x(SrTiO3)x with Modulated Band Structure and Enhanced Visible-Light Photocatalytic Activity. J Phys Chem C 113:3785–3792View ArticleGoogle Scholar
- Wang Q, Guan YP, Ren XF, Yang MZ, Liu X (2012a) Removal of low concentration Cr(VI) from aqueous solution by magnetic-fluids fixed bed using the high gradient magnetic separation. J Colloid Interf Sci 374:325–330View ArticleGoogle Scholar
- Wang DH, Jia L, Wu XL, Lu LQ, Xu AW (2012b) One-step hydrothermal synthesis of N-doped TiO2/C nanocomposites with high visible light photocatalytic activity. Nanoscale 4:576–584View ArticleGoogle Scholar
- Wang L, Li XY, Teng W, Zhao QD, Shi Y, Yue RL, Chen YF (2013a) Efficient photocatalytic reduction of aqueous Cr(VI) over flower-like SnIn4S8 microspheres under visible light illumination. J Hazard Mater 244–245:681–688View ArticleGoogle Scholar
- Wang M, Liu Q, Che YS, Zhang LF, Zhang D (2013b) Characterization and photocatalytic properties of N-doped BiVO4 synthesized via a sol-gel method. J Alloys Compd 548:70–76View ArticleGoogle Scholar
- Zhang L, Wong KH, Chen Z, Yu JC, Zhao J, Hu C, Chan CY, Wong PK (2009) AgBr-Ag-Bi2WO6 nanojunction system: a novel and efficient photocatalyst with double visible-light active components. Appl Catal A Gen 363:221–229View ArticleGoogle Scholar
- Zheng ZK, Huang BB, Qin XY, Zhang XY, Dai Y (2011) Facile synthesis of SrTiO3 hollow microspheres built as assembly of nanocubes and their associated photocatalytic activity. J Colloid Interf Sci 358:68–72View ArticleGoogle Scholar
- Zou F, Jiang Z, Qin XQ, Zhao YX, Jiang LY, Zhi JF, Xiao TC, Edwards PP (2012) Template-free synthesis of mesoporous N-doped SrTiO3 perovskite with high visible-light-driven photocatalytic activity. Chem Commun 48:8514–8516View ArticleGoogle Scholar