Photogenerated carrier transfer mechanism and photocatalysis properties of TiO₂ sensitized by Zn(II) phthalocyanine

Abstract

The Zn(II) phthalocyanine sensitized TiO₂ (ZnPc-TiO₂) nanoparticles were prepared by hydrothermal method via impregnation with ZnPc. The as-prepared photocatalysts were characterized by X-ray diffractometry (XRD) and diffuse reflectance spectroscopy (DRS), and the surface photovoltage spectroscopy (SPS) and photocatalytic degradation of rhodamine B (RhB) were studied under illuminating. The experimental results indicate that TiO₂ sensitized by ZnPc extends its absorption band into the visible region effectively, and the sensitized TiO₂ has higher activity than TiO₂ (Degussa P-25) under the simulated solar light and the visible light. Based on the DRS and SPS results, the mechanism about the photogenerated carrier transfer between TiO₂ and ZnPc is proposed. At a lower ZnPc content (⩽0.20 μmol/g), ZnPc monomer acts as the electron donor, which provides the photoinduced electrons to the conduction band of TiO₂. These photoinduced electrons can transfer to molecular oxygen (O₂), leading to the formation of active species, such as superoxide/hydroxide radicals and singlet oxygen, which is beneficial to the photocatalytic reaction. While at a higher ZnPc content (>0.20 μmol/g), the formation of ZnPc dimer results in the decrease of photocatalytic activities of ZnPc-TiO₂ photocatalyst.

Keywords

Zn(II) phthalocyanine (ZnPc) / TiO₂ / nanoparticles / photocatalyst / sensitization / photodegradation / mechanism

References

[1] CarlosA., MartínezH., EnricB.. Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods: A general review [J]. Applied Catalysis B: Environmental, 2009, 87(3/4): 105-145

[2] WitteK. D., BusuiocA. M., MeynenV., MertensM., BilbaN., TendelooV. G., CoolP., VansantE. F.. Influence of the synthesis parameters of TiO₂-SBA-15 materials on the adsorption and photodegradation of rhodamine-6G [J]. Microporous and Mesoporous Materials, 2008, 110(1): 100-110

[3] HanF., KambalaV. S. R., SrinivasanM., RajarathnamD., NaiduR.. Tailored titanium dioxide photocatalysts for the degradation of organic dyes in wastewater treatment: A review [J]. Applied Catalysis A: General, 2009, 359(1/2): 25-40

[4] ButlerM. J., GeorgeW. M., SchoonoverR. J., SazanovichI. V., TowrieM., WeinsteinJ. A.. Application of transient infrared and near infrared spectroscopy to transition metal complex excited states and intermediates [J]. Coordination Chemistry Reviews, 2007, 251(3/4): 492-514

[5] VinuR., MadrasG.. Synthesis and photoactivity of Pd substituted nano-TiO₂ [J]. Journal of Molecular Catalysis A: Chemical, 2008, 291(1/2): 5-11

[6] XiaoQ., SiZ.-c., YuZ.-m., QiuG.-zhou.. Sol-gel auto-combustion synthesis of samarium-doped TiO₂ nanoparticles and their photocatalytic activity under visible light irradiation [J]. Materials Science and Engineering B, 2007, 37(1/3): 189-194

[7] LiB., WangL.-d., KangB.-n., WangP., QiuYong.. Review of recent progress in solid-state dye-sensitized solar cells [J]. Solar Energy Materials and Solar Cells, 2006, 90(5): 549-573

[8] KiselevA., MattsonA., AnderssonM., PalmqvistA. E. C., ÖsterlundL.. Adsorption and photocatalytic degradation of diisopropyl fluorophosphate and dimethyl methylphosphonate over dry and wet rutile TiO₂ [J]. Journal of Photochemistry and Photobiology A: Chemistry, 2006, 184(1/2): 125-134

[9] LhommeL., BrosillonS., WolbertD.. Photocatalytic degradation of pesticides in pure water and a commercial agricultural solution on TiO₂ coated media [J]. Chemosphere, 2008, 70(3): 381-386

[10] EvgenidouE., FytianosK., PouliosI.. Semiconductorsensitized photodegradation of dichlorvos in water using TiO₂ and ZnO as catalysts [J]. Applied Catalysis B: Environmental, 2005, 59(1/2): 81-89

[11] IlievV., TomovaD.. Photocatalytic oxidation of sulfide ion catalyzed by phthalocyanine modified titania [J]. Catalysis Communications, 2002, 3(7): 287-292

[12] HaoY. Z., YangM. Z., YuC., CaiS. M., ZhouG. D.. Photoelectrochemical studies on acid-doped polyaniline as sensitizer for TiO₂ nanoporous film [J]. Solar Energy Materials and Solar Cells, 1998, 56(1): 75-84

[13] XinB. F., JingL. Q., RenZ. Y., WangB. Q., FuH. G.. Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of TiO₂ [J]. Journal of Physical Chemistry B, 2005, 109: 2805-2809

[14] DengH. H., MaoH. F., LiangB. J., LiJ. M., XuH. J.. Cosensitization of a nanostructured TiO₂ electrode with tetrasulfonated gallium phthalocyanine and tetrasulfonated zinc porphyrin [J]. Journal of Photochemistry and Photobiology A: Chemistry, 1997, 110(1): 47-52

[15] DerosaM. C., CrutchleyR. J.. Photosensitized singlet oxygen and its applications [J]. Coordination Chemistry Reviews, 2002, 233/234: 351-371