WO2019003079A1 - Fe 2o3/ca2fe2o 5 photocatalyst system - Google Patents

Fe 2o3/ca2fe2o 5 photocatalyst system Download PDF

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Publication number
WO2019003079A1
WO2019003079A1 PCT/IB2018/054657 IB2018054657W WO2019003079A1 WO 2019003079 A1 WO2019003079 A1 WO 2019003079A1 IB 2018054657 W IB2018054657 W IB 2018054657W WO 2019003079 A1 WO2019003079 A1 WO 2019003079A1
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photocatalyst
visible light
water
synthesis
photocatalysis
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PCT/IB2018/054657
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French (fr)
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Andris ŠUTKA
Tālis JUHNA
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Rīgas Tehniskā Universitāte
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/0018—Mixed oxides or hydroxides
    • C01G49/0036—Mixed oxides or hydroxides containing one alkaline earth metal, magnesium or lead
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/39—Photocatalytic properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B01J35/45—Nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/088—Decomposition of a metal salt

Definitions

  • the invention refers to water treatment technology sector and is intended for use in photocatalysis processes in visible light, for example, in water treatment reactors.
  • Visible-light photocatalysis is a green, reagent-free and zero-energy technology for energy harvesting and environmental remediation [1].
  • Photocatalysis is based on semiconductor oxides absorbing light with incident photon energy matching or exceeding the semiconductor's bandgap [2]. Absorbed photons excite electrons to the conduction band (CB) and leave an electron hole in the valence band (VB), thus creating photogenerated electron-hole pairs. In combination with ambient water, the electron-hole pairs trigger the formation of H 2 and 0 2 [3] or reactive oxygen species (ROS) with strong oxidation capacity for the degradation of organic substances [4].
  • Semiconductor photocatalysis has several disadvantages.
  • the most excellent photocatalytic material, T1O2 does not absorb visible light and can only be excited by ultraviolet radiation [5]. Incorporating dopants, such as nitrogen [6], sulfur [7], carbon [8] or transition metals [9], into T1O2 can add visible-light activity, but the utilized synthesis methods generally have low yield, high cost, or high ecological impact. Additionally, the resulting photocatalytic activities may be limited [10]. Narrow band gap visible-light- absorbing semiconductors (WO3, Fe203, B1VO4, etc.) have been demonstrated as promising candidates for photocatalysis [11-13], but nevertheless most have limited photocatalytic efficiency due to the fast recombination of photogenerated charge carriers.
  • Some narrow band gap photocatalysts are especially active using visible light but are not stable [14,15] and suffer from photocorrosion.
  • One of the most effective strategies to decrease the overall recombination and to improve the photocatalytic efficiency or stability is to increase the spatial separation of photogenerated charge carriers by coupling semiconductor oxides with metal and/or other semiconductors to form two- or three-component systems [16,17]. In the most common system two semiconductors are coupled with mismatched band edges, generating a potential slope at the interface, which causes electrons to migrate to the component with the more-positive CB edge and causes holes to transfer to the material with the more- negative VB edge.
  • the main drawback of such a system is a decrease of its (overall) redox potential [18].
  • the most promising photocatalytic materials are all-solid semiconductor systems with a Z-scheme photogenerated charge-transfer mechanism [19].
  • Z-scheme systems have been reported for water splitting [20], dye degradation [21] and CO2 conversion [22].
  • semiconductors with mismatched band edges are coupled via ohmic contact to position the CB and VB potentials of one semiconductor more negative than those of the other semiconductor [18].
  • Ohmic contact in a Z-scheme system triggers the recombination of electrons and electron holes with lower reduction or oxidation potential, thus leaving more reducing electrons and more oxidative holes intact
  • a particularly large amount of photogenerated holes and electrons is preserved for oxidation-reduction reactions (usually the absolutely largest majority of photoinduced electrons and holes recombine, emitting energy in the form of heat) on the surface of photocatalyst, and the oxidation-reduction potential of these charge carriers in this photocatalyst system (Z-scheme) is preserved as high as possible for the visible-light- active narrow band gap semiconductor system.
  • the closest known p- and n-type narrow band gap photocatalyst system is FeiC /CuiO [23] (selected as a prototype).
  • CmO compound used in this system is unstable [24], and a complicated solvothermal method is used for synthesis of heterostructure [23].
  • the objective of this invention is to develop a new photocatalyst system with Z-scheme photoinduced charge transfer mechanism from chemical elements widely found in nature and their semiconductor compounds with narrow band gap, using industrially applicable aqueous synthesis methods.
  • the objective of the invention is achieved by creating Z-scheme semiconductor photocatalyst system based on hematite Fe 2 03 and brownmillerite Ca2Fe 2 05 with excellent charge separation (reduced recombination), excellent visible-light harvesting ability and high redox potential.
  • Both Fe 2 03 and Ca 2 Fe 2 0 5 consist from earth abundant elements and are narrow band gap semiconductors with band gap energy approximately 2 eV.
  • hematite is n-type semiconductor
  • brownmillerite is p-type semiconductor, thus providing ohmic contact and avoiding additional synthesis steps for depostion of electronic mediators between two semiconductors in Z-scheme.
  • Hematite and brownmillerite also exhibit proper band gap positions as described below. The system was made using an aqueous synthesis to maintain green chemistry principles.
  • the Fe 2 03/Ca 2 Fe 2 0 5 system of photocatalyst compounds has the following advantages: (i) semiconductors Fe 2 03 and Ca 2 Fe 2 0 5 have narrow band gap energy; therefore, they absorb visible light— photocatalytic reactions are possible in sunlight.
  • Fe 2 03/Ca 2 Fe 2 0 5 systems of photocatalyst compounds contain chemical elements widely found in nature - Fe, Ca and O;
  • Fe 2 03 and Ca 2 Fe 2 0 5 semiconductor compounds included in the system are stable in photocatalysis reactions;
  • Fe 2 03/Ca 2 Fe 2 0 5 system of photocatalyst compounds can be generated by using industrialized aqueous-based chemical methods.
  • the Fe 2 03/Ca 2 Fe 2 0 5 system of photocatalyst compounds can be used in photocatalysis processes in visible light: (i) for water purification; (ii) disinfection; (iii) air purification; (iv) sterile surfaces; (v) water splitting; (vi) obtaining chemical compounds from ambient environment C0 2 .
  • Coatings of Fe 2 03/Ca 2 Fe 2 0 5 systems of photocatalyst compounds can serve as antibacterial or air purifying surfaces, which operate with indoor lighting.
  • Fe 2 03/Ca 2 Fe 2 0 5 system of photocatalyst compounds can be used both for generation of powder products and in coatings.
  • Powder materials can be used for production of photocatalysis reactors or improvement of already existing photocatalyst reactors, allowing using visible light as the source of light, instead of UV radiation. Sources of visible light radiation consume less energy and are considerably cheaper.
  • the method for generating Fe 2 03/Ca 2 Fe 2 ()5 systems of photocatalyst compounds is characteristic with the feature, that iron containing amorphous nano-dimensional sediment suspension is impregnated with Ca by adding Ca containing salt aqueous solution.
  • suspensions are thermally processed: (i) dried at the temperature up to 100°C— sufficient temperature to dry water, continuing the drying process until it is completely dry; (ii) thermally treated at the temperature up to 1100°C for 1 hour. Thermal treatment at higher temperatures than 1100°C can cause reduction of compounds, evaporation of any element or formation of other compounds. Longer thermal treatment process reduces the specific surface, which will reduce the activity of compounds.
  • Example 1 powder product is synthesized initially with equal volume proportions: mixing 0.1 M Fe(NC>3)3 9H 2 0 water solution with 0.5 M hexamethylenetetramine solution, obtaining Fe containing amorphous sediments. Sediments are filtered and washed with water. After washing 1 M Ca(N03) 2 aqueous solution is filtered through Fe sediment layer (concentrated suspension). Sediments after filtering are dried at the temperature of 60°C for 1 hour and are thermally treated at the temperature of 820°C for 20 minutes.
  • Example 2 during the process of coating synthesis, Fe amorphous layer is placed on a conductive substrate (working electrode) surface by using electrochemical deposition from 0,02 M FeCl 2 aqueous solution by using Pt wire as an auxiliary electrode and applying the external circuit potential 1.2V. The obtained layer is immersed in Ca(N03) 2 aqueous solution for 1 minute. The coating is dried at the temperature of 60°C for 1 hour and is thermally treated at the temperature of 820°C for 20 minutes. Sediments for production of powder and coatings are amorphous and dimensions of their separate particles are smaller than 100 nm.

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Abstract

Invention is related to water remediation technology field and is expected to be used for photocatalysis in visible light, for example, water purification reactors. Commercially available TiO2 photocatalyst is not active in visible light, because of its wide band gap (3.2 eV), but narrow bang gap semiconductors and their systems has high photoinduced charge carrier recombination and low oxidation-reduction potential. Invention here is narrow n- and p-type semiconductor system with high oxidation-reduction potential and low photoinduced charge carrier recombination, which is provided by Z-scheme charge transfer mechanism. System contains photocatalysts from earth abundant chemical elements. For synthesis of proposed photocatalyst system water based industrializable methods are used. Photocatalyst system Fe2O3/Ca2Fe2O5 can be used in visible light photocatalysis: (i) water purification; (ii) disinfection; (iii) air purification; (iv) sterile surfaces; (v) water splitting; (vi) synthesis of chemical compounds from ambient CO2.

Description

FeiCb/CaiFeiOs PHOTOCATALYST SYSTEM
The invention refers to water treatment technology sector and is intended for use in photocatalysis processes in visible light, for example, in water treatment reactors.
Visible-light photocatalysis is a green, reagent-free and zero-energy technology for energy harvesting and environmental remediation [1]. Photocatalysis is based on semiconductor oxides absorbing light with incident photon energy matching or exceeding the semiconductor's bandgap [2]. Absorbed photons excite electrons to the conduction band (CB) and leave an electron hole in the valence band (VB), thus creating photogenerated electron-hole pairs. In combination with ambient water, the electron-hole pairs trigger the formation of H2 and 02 [3] or reactive oxygen species (ROS) with strong oxidation capacity for the degradation of organic substances [4]. Semiconductor photocatalysis has several disadvantages. First, the most excellent photocatalytic material, T1O2, does not absorb visible light and can only be excited by ultraviolet radiation [5]. Incorporating dopants, such as nitrogen [6], sulfur [7], carbon [8] or transition metals [9], into T1O2 can add visible-light activity, but the utilized synthesis methods generally have low yield, high cost, or high ecological impact. Additionally, the resulting photocatalytic activities may be limited [10]. Narrow band gap visible-light- absorbing semiconductors (WO3, Fe203, B1VO4, etc.) have been demonstrated as promising candidates for photocatalysis [11-13], but nevertheless most have limited photocatalytic efficiency due to the fast recombination of photogenerated charge carriers. Some narrow band gap photocatalysts, for example, Ag20 and CU2O, are especially active using visible light but are not stable [14,15] and suffer from photocorrosion. One of the most effective strategies to decrease the overall recombination and to improve the photocatalytic efficiency or stability is to increase the spatial separation of photogenerated charge carriers by coupling semiconductor oxides with metal and/or other semiconductors to form two- or three-component systems [16,17]. In the most common system two semiconductors are coupled with mismatched band edges, generating a potential slope at the interface, which causes electrons to migrate to the component with the more-positive CB edge and causes holes to transfer to the material with the more- negative VB edge. The main drawback of such a system is a decrease of its (overall) redox potential [18]. The most promising photocatalytic materials are all-solid semiconductor systems with a Z-scheme photogenerated charge-transfer mechanism [19]. Z-scheme systems have been reported for water splitting [20], dye degradation [21] and CO2 conversion [22]. In Z-scheme systems, semiconductors with mismatched band edges are coupled via ohmic contact to position the CB and VB potentials of one semiconductor more negative than those of the other semiconductor [18]. Ohmic contact in a Z-scheme system triggers the recombination of electrons and electron holes with lower reduction or oxidation potential, thus leaving more reducing electrons and more oxidative holes intact In this case a particularly large amount of photogenerated holes and electrons is preserved for oxidation-reduction reactions (usually the absolutely largest majority of photoinduced electrons and holes recombine, emitting energy in the form of heat) on the surface of photocatalyst, and the oxidation-reduction potential of these charge carriers in this photocatalyst system (Z-scheme) is preserved as high as possible for the visible-light- active narrow band gap semiconductor system.
The main obstacles for Z-scheme practical applications are complicated (non- industrializable) multistep synthesis methods, small yields and expensive reagents. Moreover, often Z-scheme photocatalyst synthesis techniques are not green, but photocatalysis technology can be fully considered as green if the green synthesis principles have been followed. Additionally, many involved materials are rare or toxic.
The closest known p- and n-type narrow band gap photocatalyst system is FeiC /CuiO [23] (selected as a prototype). CmO compound used in this system is unstable [24], and a complicated solvothermal method is used for synthesis of heterostructure [23].
The objective of this invention is to develop a new photocatalyst system with Z-scheme photoinduced charge transfer mechanism from chemical elements widely found in nature and their semiconductor compounds with narrow band gap, using industrially applicable aqueous synthesis methods. The objective of the invention is achieved by creating Z-scheme semiconductor photocatalyst system based on hematite Fe203 and brownmillerite Ca2Fe205 with excellent charge separation (reduced recombination), excellent visible-light harvesting ability and high redox potential. Both Fe203 and Ca2Fe205 consist from earth abundant elements and are narrow band gap semiconductors with band gap energy approximately 2 eV. Moreover, hematite is n-type semiconductor, but brownmillerite is p-type semiconductor, thus providing ohmic contact and avoiding additional synthesis steps for depostion of electronic mediators between two semiconductors in Z-scheme. Hematite and brownmillerite also exhibit proper band gap positions as described below. The system was made using an aqueous synthesis to maintain green chemistry principles.
The Fe203/Ca2Fe205 system of photocatalyst compounds has the following advantages: (i) semiconductors Fe203 and Ca2Fe205 have narrow band gap energy; therefore, they absorb visible light— photocatalytic reactions are possible in sunlight. Using of sunlight serves as a basis for zero energy photocatalysis processes; (ii) Fe203/Ca2Fe205 systems of photocatalyst compounds contain chemical elements widely found in nature - Fe, Ca and O; (iii) Fe203 and Ca2Fe205 semiconductor compounds included in the system are stable in photocatalysis reactions; (iv) Fe203/Ca2Fe205 system of photocatalyst compounds can be generated by using industrialized aqueous-based chemical methods.
The Fe203/Ca2Fe205 system of photocatalyst compounds can be used in photocatalysis processes in visible light: (i) for water purification; (ii) disinfection; (iii) air purification; (iv) sterile surfaces; (v) water splitting; (vi) obtaining chemical compounds from ambient environment C02. Coatings of Fe203/Ca2Fe205 systems of photocatalyst compounds can serve as antibacterial or air purifying surfaces, which operate with indoor lighting.
Fe203/Ca2Fe205 system of photocatalyst compounds can be used both for generation of powder products and in coatings. Powder materials can be used for production of photocatalysis reactors or improvement of already existing photocatalyst reactors, allowing using visible light as the source of light, instead of UV radiation. Sources of visible light radiation consume less energy and are considerably cheaper.
The method for generating Fe203/Ca2Fe2()5 systems of photocatalyst compounds is characteristic with the feature, that iron containing amorphous nano-dimensional sediment suspension is impregnated with Ca by adding Ca containing salt aqueous solution. In next step suspensions are thermally processed: (i) dried at the temperature up to 100°C— sufficient temperature to dry water, continuing the drying process until it is completely dry; (ii) thermally treated at the temperature up to 1100°C for 1 hour. Thermal treatment at higher temperatures than 1100°C can cause reduction of compounds, evaporation of any element or formation of other compounds. Longer thermal treatment process reduces the specific surface, which will reduce the activity of compounds.
Examples for implementation of the invention
Example 1 : powder product is synthesized initially with equal volume proportions: mixing 0.1 M Fe(NC>3)3 9H20 water solution with 0.5 M hexamethylenetetramine solution, obtaining Fe containing amorphous sediments. Sediments are filtered and washed with water. After washing 1 M Ca(N03)2 aqueous solution is filtered through Fe sediment layer (concentrated suspension). Sediments after filtering are dried at the temperature of 60°C for 1 hour and are thermally treated at the temperature of 820°C for 20 minutes.
Example 2: during the process of coating synthesis, Fe amorphous layer is placed on a conductive substrate (working electrode) surface by using electrochemical deposition from 0,02 M FeCl2 aqueous solution by using Pt wire as an auxiliary electrode and applying the external circuit potential 1.2V. The obtained layer is immersed in Ca(N03)2 aqueous solution for 1 minute. The coating is dried at the temperature of 60°C for 1 hour and is thermally treated at the temperature of 820°C for 20 minutes. Sediments for production of powder and coatings are amorphous and dimensions of their separate particles are smaller than 100 nm.
References
[I] S. Dong, J. Feng, M. Fan, Y. Pi, L. Hu, X. Han, M. Liu, J. Sun, J. Sun, Recent developments in heterogeneous photocatalytic water treatment using visible lightresponsive photocatalysts: a review, RSC Adv. 5 (2015) 14610-14630.
[2] A. Fujishima, K. Honda, Electrochemical photolysis of water at a semiconductor electrode, Nature 238 (1972) 37-38.
[3] A. Kudo, Y. Miseki, Heterogeneous photocatalyst materials for water splitting, Chem. Soc. Rev. 38 (2009) 253-278.
[4] V.L. Prasanna, R. Vijayaraghavan, Insight into the mechanism of antibacterial activity of ZnO: surface defects mediated reactive oxygen species even in the dark, Langmuir 31 (2015) 9155-9162.
[5] S. Rehman, R. Ullah, A.M. Butt, N.D. Gohar, Strategies of making Ti02 and ZnO visible light active, J. Hazard. Mater. 170 (2009) 560-569.
[6] R. Asahi, T. Morikawa, T. Ohwaki, K. Aoki, Y. Taga, Visible-light photocatalysis in nitrogen-doped titanium oxides, Science 293 (2001) 269-271.
[7] H.J. Zhang, G.H. Chen, D.W. Bahnemann, Photoelectrocatalytic materials for environmental applications, J. Mater. Chem. 19 (2009) 5089-5121.
[8] F. Dong, H.Q. Wang, Z.B.J. Wu, One-step green synthetic approach for mesoporous C-doped titanium dioxide with efficient visible light photocatalytic activity, Phys. Chem. C 113 (2009) 16717-16723.
[9] D. Dvoranova, V. Brezova, M. Mazitr, M.A. Malati, Investigations of metal-doped titanium dioxide photocatalysts, Appl. Catal. B: Environ. 37 (2002) 91-105.
[10] F. Dong, S. Guo, H. Wang, X. Li, Z. Wu, Enhancement of the visible light photocatalytic activity of C-doped T1O2 nanomaterials prepared by a green synthetic approach, J. Phys. Chem. C 115 (2011) 13285-13292.
[I I] S. Tokunaga, H. Kato, A. Kudo, Selective preparation of monoclinic and tetragonal B1VO4 with scheelite structure and their photocatalytic properties, Chem. Mater. 13 (2001) 4624-4628.
[12] W. Morales, M. Cason, O. Aina, N.R. de Tacconi, K. Rajeshwar, Combustion synthesis and characterization of nanocrystalline WO3, J. Am. Chem. Soc. 130 (2008) 6318-6319.
[13] B. Ahmmad, K. Leonard, Md.S. Islam, J. Kurawaki, M. Muruganandham, T. Ohkubo, Y. Kuroda, Green synthesis of mesoporous hematite (a-Fe203) nanoparticles and their photocatalytic activity, Adv. Powder Technol. 24 (2013) 160-167.
[14] C. Yu, G. Li, S. Kumar, K. Yang, R. Jin, Phase transformation synthesis of novel Ag20/Ag2C03 heterostructures with high visible light efficiency in photocatalytic degradation of pollutants, Adv. Mater. 26 (26) (2014) 892-898.
[15] L. Huang, F. Peng, H. Yu, H. Wang, Preparation of cuprous oxides with different sizes and their behaviors of adsorption, visible-light driven photocatalysis and photocorrosion, Solid State Sci. 11 (2009) 129-138.
[16] H. Wang, L. Zhang, Z. Chen, J. Hu, S. Li, Z. Wang, J. Liu, X. Wang, Semiconductor heteroj unction photocatalysts: design, construction, and photocatalytic performances, Chem. Soc. Rev. 43 (2014) 5234-5244.
[17] H. Li, Y. Zhou, W. Tu, J. Ye, Z. Zou, State-of-the-art progress in diverse heterostructured photocatalysts toward promoting photocatalytic performance, Adv. Fund Mater. 25 (2015) 998-1013.
[18] P. Zhou, J. Yu, M. Jaroniec, All-solid-state Z-scheme photocatalytic systems, Adv. Mater. 26 (2014) 4920-4935.
[19] H. Li, W. Tu, Y. Zhou, Z. Zou, Z-scheme photocatalytic systems for promoting photocatalytic performance: recent progress and future challenges, Adv. Sci. 3 (2016) 1500389.
[20] L.J. Zhang, S. Li, B.K. Liu, D.J. Wang, T.F. Xie, Highly efficient CdS/W03 photocatalysts: Z-scheme photocatalytic mechanism for their enhanced photocatalytic H2 evolution under visible light, ACS Catal. 4 (2014) 3724-3729.
[21] W.K. Jo, T. Adinaveen, J.J. Vijaya, N.C.S. Selvam, Synthesis of M0S2 nanosheet supported Z-scheme Ti02/g-C3N4 photocatalysts for the enhanced photocatalytic degradation of organic water pollutants, RSC Adv. 6 (2016) 10487-10497.
[22] J.-C. Wang, H.-Ch. Yao, Z.-Y. Fan, L. Zhang, J.-S. Wang, S.-Q. Zang, Z.-J. Li, Indirect Z-scheme BiOI/g-C3N4 photocatalysts with enhanced photoreduction CO2 activity under visible light irradiation, ACS Appl. Mater. Interfaces 8 (2016) 3765-3775.
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Claims

Photocatalyst system of n- and p-type narrow band gap semiconductors with Z- scheme photoinduced charge carrier transfer mechanism that includes Fe203 and further contains Ca2Fe205.
Method for preparation of photocatalyst system according to claim 1, wherein amorphous iron containing nanoparticle precipitates sediments in a form of suspension are impregnated with Ca salt aqueous solution, dried at the temperature up to 100°C and additionally thermally treated at the temperature up to 1100°C for 1 hour.
Method according to claim 2, wherein drying is realized at about 60°C.
Method according to any of claims 2 to 3, wherein drying is realized for up to 1 hour.
Method according to any of claims 2 to 4, wherein thermal treatment is realized at about 820°C.
Method according to any of claims 2 to 5, wherein thermal treatment is realized for 20 minutes.
PCT/IB2018/054657 2017-06-26 2018-06-25 Fe 2o3/ca2fe2o 5 photocatalyst system WO2019003079A1 (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
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CN109589959A (en) * 2019-01-23 2019-04-09 西北师范大学 α-di-iron trioxide/titanic oxide nano compound material preparation and the application in photocatalytic reduction of carbon oxide
CN111871408A (en) * 2020-07-16 2020-11-03 浙江工业大学 Direct Z-Scheme heterojunction catalyst and preparation method and application thereof
LV15557A (en) * 2020-06-19 2021-03-20 Rīgas Tehniskā Universitāte A method for water disinfection using cafeo
CN112811476A (en) * 2020-12-31 2021-05-18 华中科技大学 Nickel-doped brownmillerite type oxygen carrier and preparation method and application thereof
CZ309898B6 (en) * 2022-06-29 2024-01-17 Vysoká škola chemicko-technologická v Praze A method of preparing the structure of a Z-schematic photocatalyst for splitting water

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