硼掺杂二氧化钛提高光催化性能
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摘要
以纳米锐钛矿二氧化钛(TiO_2)为原料、硼氢化钠(NaBH_4)为硼源和还原剂,采用一步水热法制备了硼(B)掺杂含有氧空位的B/TiO_2光催化剂。利用X射线衍射(XRD)、红外光谱(IR)、紫外-可见漫反射光谱(DRS)、X射线电子能谱(XPS)、电子顺磁共振谱(EPR)等,对样品进行结构及性能表征。以亚甲基蓝(MB)作为目标降解物,进行光催化实验,考察B掺杂与氧空位对TiO_2光催化性能的影响。结果表明,在紫外光照射下,B/TiO_2催化反应的一级反应速率常数是单一相TiO_2的1.7倍;在可见光照射下,B/TiO_2催化反应的一级反应速率常数是纯石墨相氮化碳(g-C_3N_4)的3.2倍。反应活性物种的捕获实验表明,在体系中起光催化氧化作用的活性物种主要是空穴。光催化活性的提高归因于:适量的B掺杂和合适的氧空位的协同作用。适量的B掺杂可使TiO_2的载流子捕获位增多,有效增加了样品光催化反应的氧化位点,延长了载流子的寿命和有利于电荷的传递;合适的氧空位可拓宽其光吸收范围和提高光生载流子的传导性。
By using one-step hydrothermal method, anoxic state of boron(B)-doped B/TiO_2 photocatalysts were synthesized, TiO_2 taken as raw material, and sodium borohydride as the boron source and reducing agent, respectively. The structure and properties of the samples were characterized by X-ray powder diffraction(XRD), infrared spectroscopy(IR), ultraviolet-visible diffuse reflectance spectroscopy(DRS), X-ray electron spectroscopy(XPS) and electron paramagnetic resonance(EPR), respectively. Photocatalytic performance test was carried out to investigate the effect of B doping and oxygen vacancy on the photocatalytic activity of titanium dioxide by using methylene blue(MB) as the degradation target. The results showed that the first-order reaction rate constant of B/TiO_2 under ultraviolet irradiation was 1.7 times that of single phase TiO_2; and under visible irradiation it was 3.2 times the constant of pure graphite carbon nitride(g-C_3N_4). The capture experiments of reactive species showed that the main active species for photocatalytic oxidation in this system were holes. The enhancement of photocatalytic activity of TiO_2 could be attributed to the proper B doping,which could increase the carriers trapping sites of TiO_2 and the oxidation sites, prolonging the lifetime of carriers and facilitating charge transfer. The appropriate oxygen vacancy concentration could broaden the light absorption range and improve the conductivity of photogenerated carriers. The synergistic effect of the two enhanced the photocatalytic activity.
By using one-step hydrothermal method, anoxic state of boron(B)-doped B/TiO_2 photocatalysts were synthesized, TiO_2 taken as raw material, and sodium borohydride as the boron source and reducing agent, respectively. The structure and properties of the samples were characterized by X-ray powder diffraction(XRD), infrared spectroscopy(IR), ultraviolet-visible diffuse reflectance spectroscopy(DRS), X-ray electron spectroscopy(XPS) and electron paramagnetic resonance(EPR), respectively. Photocatalytic performance test was carried out to investigate the effect of B doping and oxygen vacancy on the photocatalytic activity of titanium dioxide by using methylene blue(MB) as the degradation target. The results showed that the first-order reaction rate constant of B/TiO_2 under ultraviolet irradiation was 1.7 times that of single phase TiO_2; and under visible irradiation it was 3.2 times the constant of pure graphite carbon nitride(g-C_3N_4). The capture experiments of reactive species showed that the main active species for photocatalytic oxidation in this system were holes. The enhancement of photocatalytic activity of TiO_2 could be attributed to the proper B doping,which could increase the carriers trapping sites of TiO_2 and the oxidation sites, prolonging the lifetime of carriers and facilitating charge transfer. The appropriate oxygen vacancy concentration could broaden the light absorption range and improve the conductivity of photogenerated carriers. The synergistic effect of the two enhanced the photocatalytic activity.
引文
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[24] FEI X X, XIONG Y Y. Preparation and characterization of nitrogen-doped TiO2nano-powder absorbing visible light[J].Journal of functional materials and devices, 2005, 11(2):223-227.
[2] SUN S, DING J J, BAO J, et al. Photocatalytic degradation of gaseous toluene on Fe-TiO2under visible light irradiation:a study on the structure, activity and deactivation mechanism[J]. Applied surface science, 2012, 258(12):5031-5037.
[3] ASAHI R, MORIKAWA T, OHWAKI T, et al. Visiblelight photocatalysis in nitrogen-doped titanium oxides[J].Science, 2001, 293(5528):269-271.
[4] UMEBAYASHI T, YAMAKI T, TANKKA S, et al, Visilelight-induced degradation of methylene blue on S-doped TiO2[J]. Chemistry letters, 2003, 32(4):330-331.
[5] LIN X X, RONG F, FU D G, et al. Enhanced photocatalytic activity of fluorine doped TiO2by loaded with Ag for degradation of organic pollutants[J]. Powder technology,2012, 219:173-178.
[6] CHELA J, OILIS D F, RUIKENS W H, et al. Kinetic processes of photocatalytic mineralization of alcohols on metallized titanium dioxide[J]. Water Res, 1999, 33(5):1173-1180.
[7] WANG F F, ZHENG Z, JIA F L. Enhanced photoelectrochemical water splitting on Pt-loaded TiO2nanorods array thin film[J]. Materials letters, 2012, 71:141-144.
[8] WANG P, ZAKEERUDDIN S M, MOSER E, et al. A stable quasi-solid-state dye-sensitized solar cell with an ampbiphilic ruthenium sensitizer and polymer gel electrolyte[J]. Nature mater, 2003, 2(6):402-407.
[9] TURMER G M, BEARD M C, SCHMUTTENMAER C A.Carrier localization and cooling in dye-sensitized nanocrystalline titanium dioxide[J]. Journal of physical chemistry B, 2002, 106(45):11716-11719.
[10] SHI J W, YAN X X, CUI H J, et al. Low-temperature synthesis of CdS/TiO2composite photocatalysts:Influence of synthetic procedure on photocatalytic activity under visible light[J]. Journal of molecular catalysis A:chemical,2012, 356:53-60.
[11] DANIEL S, LIKIUS, HIROKI N, et al. Percolation threshold for electrical resistivity of Ag-nanoparticle/titania composite thin films fabricated using molecular precursor method[J]. J Mater Sci, 2012, 47:3890-3899.
[12] ZALESKA A, SOBCZAK J W, GRABOWSKA E, et al.Preparation and photocatalytic activity of boron-modified Ti O2under UV and visible light[J]. Appl Catal B:environ,2008, 78(1/2):92-100.
[13] ZALESKA A, GRABOWSKA E, SOBCZAK J W, et al.Photocatalytic activity of Boron-modified TiO2under visible light:the effect of Boron content, calcination temperature and TiO2matrix[J]. Appl Catal B:environ,2009, 89(3/4):469-475.
[14] CHEN D M, YANG D, WANG Q, et al. Effect of boron doping on photocatalytic activity and microstructure of titanium dioxide nanoparticles[J]. Industrial&engineering chemistry research, 2006, 45(12):4110-4116.
[15] GOMBAC V, ROGATIS L D, GASPAROTTO A, et al.TiO2nanopowders doped with boron and nitrogen for photocatalytic applications[J]. Chemical physic, 2007,339(1/2/3):111-117.
[16] XU J J, AO Y H, CHEN M D, et al. Low-temperature preparation of boron-doped titania by hydrothermal method and its photocatalytic activity[J]. Journal of alloys and compounds, 2009, 484(1/2):73-79.
[17] ZHOU Y S, CHEN F L, LIU M, et al. Dopant-induced electron localization drives CO2reduction to C2hydrocarbons[J]. Nature chemistry, 2018, 10:974–980.
[18] YAN S C, LI Z S, ZOU Z G. Photodegradation of rhodamine B and methyl orange over Boron-doped g-C3N4under visible light irradiation[J]. Langmuir, 2010, 26(6):3894-3901.
[19] JIANG X, ZHANG Y, JIANG J, et al. Characterization of oxygen vacancy associates within hydrogenated TiO2:a positron annihilation study[J]. The journal of physical chemistry C, 2012, 116(42):22619-22624.
[20] WANG W, LU C H, NI Y R, et al. Enhanced visible-light photoactivity of{001}facets dominated TiO2nanosheets with even distributed bulk oxygen vacancy and Ti3+[J].Catalysis communications, 2012, 22:19-23.
[21] LIU X G, BI Y P. In situ preparation of oxygen-deficient TiO2microspheres with modified{001}facets for enhanced photocatalytic activity[J]. RSC advances, 2017, 7(16):9902-9907.
[22] PAN Y X, SUN Z Q, CONG H P, et al. Photocatalytic CO2reduction highly enhanced by oxygen vacancies on Ptnanoparticle-dispersed gallium oxide[J]. Nano research,2016, 9(6):1689-1700.
[23] LU N, QUAN X, LI J Y. Fabrication of boron-doped TiO2nanotubearrayeleetrodeandinvestigationofitsphotoelectrochemical capability[J]. J Phys Chem C, 2007, 111:11836-11841.
[24] FEI X X, XIONG Y Y. Preparation and characterization of nitrogen-doped TiO2nano-powder absorbing visible light[J].Journal of functional materials and devices, 2005, 11(2):223-227.