DE102009044926A1 - Photocatalyst device, useful for photocatalytic decomposition of organic substances, comprises a light-guiding element and a photocatalytic substance (comprising e.g. nitrogen-doped titanium dioxide) arranged on the light-guiding element - Google Patents

Abstract

Photocatalyst device comprises a light-guiding element and a photocatalytic substance arranged on the light-guiding element, where the photocatalytic substance comprises bismuth oxide, nitrogen-doped, carbon-doped or sulfur-doped titanium dioxide and/or a binary bismuth metal oxide compounds.

Description

The invention relates to a photocatalyst device having a light element and a photocatalytic substance arranged on the light element.

Photocatalysis, and more specifically photoassisted catalytic reaction, in which a catalyst substance is brought into an excited state under the action of light of suitable wavelength, which then provides the necessary energy for subsequent reduction and / or oxidation, has been described many times in the literature. The photocatalytic substance used is titanium dioxide (TiO ₂ ), in particular in the form of anatase. Well-known applications include wastewater or waste gas purification, photovoltaics, photocatalytic self-cleaning or artificial photosynthesis.

The aforementioned photocatalyst devices for the decomposition of organic compounds, in particular for exhaust aftertreatment are known from numerous publications. By way of example, the patent specification US 5,564,065 in which a filter arrangement for the oxidation of carbon monoxide in exhaust gases is described. The filter assembly comprises a tissue of titanium dioxide coated fiber material, an adjacent optical fiber for emitting stray light, a UV light source connected to the optical fiber, and an exhaust conduit for passing exhaust gas through the tissue of the fiber material.

From the patent US 6,324,329 B1 For example, there is known a photocatalyst device in which a multilayer optical waveguide structure on a substrate is provided with a titania photocatalyst layer. Light having an intensity maximum at a wavelength of about 400 nm is coupled from an artificial light source into a light guide layer of Ta ₂ O ₅ or polymethyl methacrylate (PMMA). The light enters the photoconductor layer into a TiO ₂ photocatalyst layer located either directly on the photoconductor layer or into the photocatalyst layer via an interposed buffer layer, favoring adjustment of layer thicknesses and refractive indices, and placing the titanium dioxide in an excited state for a subsequent catalytic reaction ,

Also from the EP 1 008 565 A1 For example, a photocatalyst device based on a TiO ₂ coating is known. The photocatalytic substance is applied in a sol-gel process in several dipping and drying steps on a glass fiber. The glass fiber is processed into a thread, a rope or a fabric, which can be used as a photocatalyst device for the decomposition of organic substances.

Also in the US 6,468,428 B1 For example, a titania film is applied in a sol-gel process to an aluminum silicate glass fiber substrate having a plurality of protrusions or nubs along its peripheral surface. A plurality of such fibers are combined into a bundle, wherein the nubs keep the glass fibers in the shape at a distance, that a sufficiently large cavity for the passage of exhaust gases is formed. Instead of the glass fiber bundle, the glass fiber can also be braided into a net, processed into a fabric or formed into a ball. Furthermore, a honeycomb optical waveguide structure and an arrangement of parallel light guide plates is presented. The photocatalyst device is intended for use in a diesel particulate filter (DPF).

A development of the photocatalyst device bundled with. Glass fibers is from the US 6,764,655 B1 known, wherein the glass fibers are surrounded by granular spacers and are arranged in parallel in an elongated housing, which is flowed through in the longitudinal direction of exhaust gas.

The U.S. Patent 6,685,889 B1 discloses a photo-conductive catalyst based on a photoconductive fiber coated with a zeolite layer as a catalytic substance in a sol-gel dip coating process. If the photoconductive fiber is encased, the cladding is removed at least on a portion of the photoconductive fiber on which the zeolite crystal layer is then deposited.

The suitability of titanium dioxide as a photocatalytic substance is due to its semiconductor property with a band gap whose energy gap corresponds to a light wavelength of about 390 nm. Light with this or a shorter wavelength can create electron-hole pairs in the material, that is to say an internal photoelectric effect, which forms the starting point for generating radicals for the decomposition of organic substances. Thus, as excitation energy predominantly only ultraviolet light comes into question, which makes up only a very small proportion of the visible fraction of terrestrial solar radiation. For an efficient photocatalytic effect is therefore an artificial Light source needed. Furthermore, the use of UV light has the disadvantage that for the light pipe only quartz glasses can be used and a variety of less expensive optical fiber materials in this spectral range is unsuitable.

The object against the background of the above prior art is to provide a photocatalyst device of the type mentioned, which also allows the use of light of different wavelength, in particular visible light, an efficient photocatalytic decomposition of organic substances and also cost in their production is.

The object is achieved by a photocatalyst device with the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

As a photocatalytic reaction in the sense of this document, so-called photosensitized reactions are understood. In reactions of this type, the substance called photocatalyst or photocatalytic (active) is converted by light into an electronically excited state in which it is then catalytically active. For some of the substances referred to below as photocatalytic, there are indications that these could not be catalysts in the strict sense, since they react or transform during the course of the reaction, whereby their photocatalytic activity is lost. Strictly speaking, one would have to speak of a "photoreaction" assisted by these substances. In the context of this application, photocatalytic reactions are understood as meaning both the classic photosensitized catalytic reactions and the photoreactions assisted in the above sense.

According to the invention, the photocatalytic substance Bi ₂ O ₃ and / or N-doped TiO ₂ and / or C-doped TiO ₂ and / or S-doped TiO ₂ and / or a binary bismuth metal oxide compound, in particular a compound of the Group MBiO ₃ · xH ₂ O, with M = alkali, x ≥ 0, BiVO ₄ , Bi ₂ MoO ₆ and Bi ₂ WO ₆ .

Bismuth oxide has an electronic band gap of 2.3 to 2.9 eV as a function of the preparation of the bismuth oxide powder and is therefore substantially less limited in terms of its photocatalytic activity than TiO ₂ , whose band gap is significantly greater than 3.0 eV. This corresponds to a light wavelength of 540 nm to 427 nm and thus in each case an excitation energy which is completely in the range of visible light. Specifically, it has been found that bismuth oxide as a photocatalytic substance using light having a wavelength greater than 420 nm has an extremely high photoactivity. This enables an efficient photocatalytically assisted decomposition reaction of organic substances using terrestrial solar radiation and thus without the need for an additional UV light source. A similarly high photoactivity could also be recorded using C-doped TiO ₂ , while N-doped TiO _{2 has} a photoactivity reduced by about 30%. Also, a doping of the titanium dioxide with sulfur leads to a reduction in the band gap and thus compared to undoped TiO ₂ to increased photocatalytic activity.

The photocatalytic substance preferably has α-Bi ₂ O ₃ and / or β-Bi ₂ O ₃ .

It has proved to be advantageous that the light-guiding element is at least one optical fiber, in particular a refractive index-matched optical fiber with a light-guiding core, along the outer peripheral surface of which scattering centers and the photocatalytic layer are arranged.

For the purposes of this specification, a refractive index-matched optical fiber is understood to be a light-conducting fiber which consists either of a fiber core alone or else of a fiber core and at least one sheath enclosing the core along the fiber axis. In the first case, the light conduction takes place in the fiber core by total reflection of the guided in the core light at the interface between the fiber core and the surrounding medium, in the second case by total reflection at the interface between the cladding and the surrounding medium, if the surrounding medium has a smaller refractive index as the coat has.

If the fiber core along the fiber axis surrounded by at least one jacket, the total reflection and thus the light pipe occurs when the cladding has a substantially at least the same refractive index as the fiber core, so that the light can first decouple from the core into the cladding , The light is thus guided in the system as a core and mantle. In this case, one also speaks of a refractive index matched core-sheath fiber.

Since in general the best possible guidance of the light in the fiber is sought, ie that as little light as possible is lost in the coupling into the fiber, an adjustment of the refractive index the fiber core (in the case of the core fiber) or the shell (in the case of the core-sheath fiber) is made by suitable choice of material, so that the critical angle at which total reflection takes place at the interface with the surrounding medium is set in a suitable manner.

For the purposes of this specification, side-emitting means that the fiber is able to emit light laterally, irrespective of whether it is in operation, ie. H. whether a light source is actually connected and the light is on.

A side-emitting refractive index matched fiber is accordingly a refractive index matched fiber in which light is intentionally extracted from the fiber. This is done by the scattering centers arranged along the outer circumferential surface of the optical fiber. Thus, in the case of the core fiber, the scattering centers are disposed on the outer circumferential surface of the core and, in the case of the core-sheath fiber, on the outer peripheral surface of the shell.

For the purposes of the invention, the term scattering centers is understood to mean, in particular, scattering particles which, irrespective of their shape, material and / or size, can scatter the conducted light. Scattering particles can unfold their scattering effect by classical scattering, in particular Rayleigh and / or Mie scattering, as well as by diffraction and / or reflection as well as multiple processes of the aforementioned type. Their task is to deflect individually or in their total incident light in such a way that it leaves the fiber.

In general, since uniform decoupling is desired along the entire length of the optical fiber, which makes a side-emitting refractive index matched optical fiber appear ideally as a uniformly luminous band or line, the scattering centers are preferably distributed as homogeneously as possible on the outer peripheral surface.

According to an alternative embodiment, the optical fiber is advantageously a side-emitting step index fiber having a transparent and / or translucent cladding surrounding the core, wherein scattering centers between the cladding and the core and the photocatalytic layer are disposed on the cladding.

As a step index fiber in the context of this document fibers are understood in which the light conduction takes place in the fiber core by total reflection of the light guided in the core at the interface to the enclosing jacket. This total reflection occurs when the cladding has a lower refractive index than that of the photoconductive fiber core and that only up to a critical angle β _min of the light striking the cladding, which according to sin (β _min ) = n ₂ / n ₁ with n ₁ = refractive index of the fiber core and n ₂ = refractive index of the cladding can be determined, wherein β _{min is} measured starting from a plane perpendicular to the fiber axis.

The effect of the side emission is generated in this embodiment of the invention by scattering the guided light in the core in a thin in relation to the core diameter scattering area between the core and cladding. Responsible for the scattering are the scattering centers, which are stored in the scattering area. For the purposes of this embodiment, scattering centers are all entities of whatever shape, material, and / or size that can scatter the guided light and those due to inhomogeneous regions of the glass in which they are incorporated, or scattering particles of a different material than the glass in which they are embedded. Their task is, as described above, to deflect individually or in their total incident light, so that it can leave the optical fiber in the surrounding medium. Specifically come as a scattering centers, for example, scattering particles in question, which are embedded in the scattering between the core and the shell, for example, in a glass layer. Alternatively, the scattering centers may be formed by inhomogeneous regions of a glass interposed between the core and the cladding. In the former case, the refractive index of the glass forming the scattering region is, if possible, equal to the refractive index of the core, so that the light can pass unhindered to the scattering particles embedded therein.

In the latter case, the refractive index of the embedded glass layer with inhomogeneities may differ from that of the core and / or of the shell.

On the way into the surrounding medium, the side-emitted light then strikes the photocatalytic substance arranged along the outer circumferential surface of the optical fiber or the jacket and stimulates the latter to form an electron-hole pair.

The optical fiber of glass fiber consisting of a core glass and a cladding glass particularly preferably has one of the following compositions: Core glass variant 1 with refractive index n ₁ of 1.65 to 1.75, including (in mol% based on oxide) SiO ₂ 25 to 45 B ₂ O ₃ 13 to 25 CaO 0 to 16 SrO 0 to 8 BaO 17 to 35 La ₂ O ₃ 2 to 12 Ta ₂ O ₅ 0.1 to 6 ZrO ₂ 0.1 to 8 ZnO 0.1 to 8 CaO + SrO + BaO + ZnO > 33 Al ₂ O ₃ 0 to 5 Core glass variant 2 with refractive index n ₁ of 1.65 to 1.75, containing (in mol% on oxide basis) SiO ₂ 54.5 to 65 ZnO 18.5 to 30 Sum of alkali oxides 8 to 20 La ₂ O ₃ 0 to 3 ZrO ₂ 2 to 5 HfO ₂ 0.02 to 5 ZrO ₂ + HfO ₂ 2.02 to 5 BaO 0.4 to 6 SrO 0 to 6 MgO 0 to 2 CaO 0 to 2 Sum of alkaline earth oxides 0.4 to 6 Li ₂ O 0.5 to 3, but not more than 25 mol% of the sum of alkali oxides SiO ₂ + ZrO ₂ + HfO ₂ > 58.5 ZnO ratio: sum of alkaline earth oxides> 3.5: 1 Core glass variant 3 with refractive index n ₁ of 1.58 to 1.65, including (in mol% on oxide basis) SiO ₂ 50 to 60 B ₂ O ₃ 0 to 15 BaO 10 to 35 SrO 0 to 18 Sr + Ba 10 to 35 ZnO 0 to 15 Sr + Ba + Zn 10 to 40 B ₂ O ₃ + ZnO 5 to 35 Al ₂ O ₃ 0.1 to 1.9 ZrO ₂ 0 to 4 La ₂ O ₃ 0 to 4 Y ₂ O ₃ 0 to 4 Nb ₂ O ₅ 0 to 4 La ₂ O ₃ + Y ₂ O ₃ + Nb ₂ O ₅ 0 to 4 Na ₂ O 4.5 to 10 K ₂ O 0.1 to 1 Rb ₂ O 0 to 1.5 Cs ₂ O 0 to 1.5 Rb ₂ O + Cs ₂ O 0 to 1.5 Sum of alkaline earth oxides 4.8 to 11 MgO 0 to 6 CaO 0 to <5 Core glass variant 4 containing (in% by weight based on oxide) SiO ₂ 42 to 53 ZnO 30 to 38 Na ₂ O <14 K ₂ O <12 Na ₂ O + K ₂ O ≥ 2 BaO <0.9 Core glass variant 5 containing (in% by weight based on oxide) SiO ₂ 30 to 45 B ₂ O ₃ <12 ZnO <10 BaO 25 to 40 Na ₂ O <10 K ₂ O <2 Al ₂ O ₃ <1 La ₂ O ₃ <10 Jacket glass variant 1 (in% by weight based on oxide), including SiO ₂ 70 to 78 Al ₂ O ₃ 0 to 10 B ₂ O ₃ 5 to 14 Na ₂ O 0 to 10 K ₂ O 0 to 10 Mg0 0 to 1 Ca0 0 to 2 SrO 0 to 1 BaO 0 to 1 F 0 to 1 and essentially no Li ₂ O. Jacket glass variant 2 (in% by weight based on oxide), including SiO ₂ 63 to 75 Al ₂ O ₃ 1 to 7 B ₂ O ₃ 0 to 3 Na ₂ O 8 to 20 K ₂ O 0 to 6 MgO 0 to 5 CaO 1 to 9 BaO 0 to 5 F 0 to 1 and essentially no Li ₂ O. Jacket glass variant 3 (in% by weight based on oxide), including SiO ₂ 75 to 85 Al ₂ O ₃ 1 to 5 B ₂ O ₃ 10 to 14 Na ₂ O 2 to 8 K ₂ O 0 to 1 and substantially no Li ₂ O and MgO. Jacket glass variant 4 (in% by weight based on oxide), including SiO ₂ 62 to 70 B ₂ O ₃ > 15 Li ₂ O > 0.1 Na ₂ O 0 to 10 K ₂ O 0 to 10 MgO 0 to 5 CaO 0 to 5 SrO 0 to 5 BaO 0 to 5 ZnO 0 to 5 F 0 to 1 Jacket glass variant 5 (in% by weight based on oxide), including SiO ₂ 60 to 72 B ₂ O ₃ <20 Al ₂ O ₃ <10 Na ₂ O <18 K ₂ O <15 Li ₂ O <5 F ≤ 1 Casing variant 6 (in% by weight based on oxide), including SiO ₂ 72-78 B ₂ O ₃ 5 to 15 Al ₂ O ₃ 5 to 10 Na ₂ O <10 K ₂ O <10 Li ₂ O <5 F ≤ 1 Jacket glass variant 7 (in% by weight based on oxide), including SiO ₂ 70-80 B ₂ O ₃ <5 Al ₂ O ₃ <10 La ₂ O ₃ <2 Na ₂ O <10 K ₂ O <10 ZrO ₂ <2

The glasses are known as such in the literature and can, for example, the SCHOTT series of publications "SCHOTT Series on Glass and Glass Ceramics - Science, Technology and Applications", The Properties of Optical Glass (1995, 2nd, corr. Ed., 1998), Bach, Neuroth (Eds.) , as well as the references listed here.

In a further embodiment, the light-guiding element has a plate-shaped substrate, particularly preferably a flat or float glass based on soda lime or borosilicate. It is also possible, by the parallel arrangement of a plurality of optical fibers, to form a plate-shaped light-guiding element consisting of fibers.

Alternatively, one of the plastics enumerated below may preferably also be used as the substrate for the light-guiding element:
Polycarbonate (PC), polyacrylate (P), polymethyl methacrylate (PMMA), cycloolefinic copolymer (COC), ethylene-vinyl acetate copolymer (EVA), polystyrene (PS), styrene-acrylonitrile (SAN), fluorinated polymers, such as. As polyvinylidene fluoride (PVDF), Perflouralkoxy copolymer (PFA), or partially fluorinated polymers of the aforementioned plastics.

As with the glasses, a plastic light guide can be composed of several layers to make an refractive index adjustment. Also, the waveguide made of plastic may be formed as a plate or as a fiber.

In addition, combinations of plastics and inorganic materials are possible. This is particularly advantageous if the plastic itself would be decomposed by the high photocatalytic activity of the active substance. It is particularly advantageous here if the plastic is separated from the photocatalytic material by an inorganic protective layer. Suitable materials for such a protective layer are, for example, SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ and further metal oxides. The protective layers can be applied by conventional coating methods such as vapor deposition, sputtering, flame treatment or liquid coating, in particular by the sol-gel method.

Optical fibers are particularly suitable for forming a substrate, since they can be manufactured in a known manner with long lengths and thus with a large surface in a relatively inexpensive process.

Preferably, the at least one optical fiber of the light guide is formed into a net, fabric or ball.

In this way, in a relatively small volume, a large length of optical fibers and thus a large reaction surface of the light guiding member for applying the photocatalytic substance can be provided. At the same time such a net, fabric or ball is sufficiently open-meshed or open-pored, so that when it is embedded in a housing, it allows the passage of fluids to be purified (waste gas or wastewater).

According to a preferred aspect of the invention, the photocatalytic substance in the form of particles, in particular nanoparticles, is attached to carrier particles and this particle composite is embedded as a loose powder in the mesh, tissue or balls of the optical fiber.

This only loose embedding of the photocatalytically active substance as a powder has the advantage that the photocatalytically active material is applied after the production of the light guide and avoid costly coating steps. In addition, the material forming the light guide element can be processed without regard to any damage to the coating, so that one is very flexible in terms of design and shaping.

The carrier particle material are materials which are usually used as carriers for catalytically active materials, that is, for example, metal oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ . The particular advantage of this embodiment lies in the interaction between the carrier material and the catalytically active substance. In the case of supported catalysts, the activity is generally increased with suitable reaction control, since the catalytically active substance separates out in a particularly finely divided manner and is thus particularly reactive.

Alternatively or additionally, the light-guiding element may be coated with particles, in particular with nanoparticles, of the photocatalytic one.

For the purposes of the application, nanoparticles are particles having a size of from 1 to 300 nm, particularly preferably from 1 to 100 nm. The advantage of using particles, preferably nanoparticles, is that they allow the catalyst available to be catalytically can specifically set effective surface. When using nanoparticles has the additional advantage that due to the high surface-to-volume ratio of the photocatalytic material is present in a particularly high-energy and thus active state.

As a coating method for the coating with the photocatalytically active substance, for example, the liquid coating in a sol-gel process, the physical vapor deposition (PVD), in particular sputtering, chemical vapor deposition (CVD) or plasma spraying in question.

The photocatalytic substance can be applied in one way or another in a layer directly to the outermost layer of the light-conducting element (sheath or protective layer). In this case, it is possible both for a homogeneous layer to be formed exclusively from the photocatalytically active material or for a carrier layer in which individualized particles, preferably nanoparticles, of the photocatalytic substance are embedded. In particular, SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ and further metal oxides may be considered as matrix materials for the carrier layer.

It is particularly preferred if the particles or nanoparticles are only partially embedded in the carrier layer, for example only ¼ to ½ of their diameter, and otherwise protrude out of the surface of the carrier layer.

In the further course, the optical fibers thus produced are processed into the net, fabric or ball.

Alternatively or additionally, first of the untreated or coated in the manner described above optical fibers, the network, fabric or ball are formed, which then then as a whole (again) is provided with a layer of photocatalytically active material. Again, this may be formed as a homogeneous coating of the desired photocatalyst material or as a carrier layer with particles, preferably nanoparticles, the photocatalytically active substance. And oh, it is particularly preferred if the particles are only partially embedded in the carrier layer and, moreover, protrude out of the surface of the carrier layer.

If the photocatalytically active substance in the form of particles or nanoparticles is introduced into the system, a further preferred embodiment consists in that the particles or nanoparticles are applied directly to the surface of the light-conducting element and adhere directly to it. This can be done, for example, with optical fibers during fiber blending, or with flat glass substrates following hot forming, when the surface of the glass is still relatively warm and the particles or nanoparticles adhere well to it, as well as with plastics during molding. In this way, a particularly good bond between the photocatalytically active particles and the photoconductive substrate is made possible. Here, too, an embodiment is particularly preferred in which the particles or nanoparticles protrude in part from the substrate surface, since this means an enlargement of the surface available to the system for catalysis.

Preferably, the light guide element has a roughened surface.

By this measure, scattering centers are generated in a simple and cost-effective manner, which scatter the light guided in the light guide element partially from the light guide. The photocatalytic substance is logically applied to the roughened surface.

As an alternative to a roughened surface, in general (ie not just an optical fiber), the light-guiding element can have an outer surface, arranged on the scattering centers or embedded in the scattering centers.

The scattering centers can thus be arranged in the form of particles, as in the case of the side-emitting optical fibers on the outer surface or in a refractive-index-adapted cladding layer of the light-guiding element.

In another advantageous embodiment, the light guide element consists of a bundle of optical fibers which have break points in different positions in the longitudinal direction of the fiber bundle.

Thus, a plurality of optical fibers can cause the entire bundle to emit light uniformly over a larger portion in the longitudinal direction of the bundle as needed, or concentrated to specific portions. At appropriate points then the particles of the photocatalytic substance are also applied.

The photocatalyst device preferably has an artificial light source with radiation maximum in the visible spectrum. The artificial light source is in light-conducting connection with the light-guiding element.

The artificial light source particularly preferably has at least one LED, incandescent lamp or gas discharge lamp.

The aforementioned light sources are inexpensive with high efficiency, especially in comparison with UV light sources.

In a particularly preferred embodiment, the light source is formed by sunlight. Accordingly, the photocatalyst device has means for collecting sunlight, which are in photoconductive connection with the light-guiding element.

Other objects, features and advantages of the invention will be explained in more detail by means of embodiments with the aid of the drawings.

Show it:

1 a first embodiment of the photocatalytic cleaning device according to the invention using a plurality of optical fibers as light guide elements;

2 a section of a plate-shaped light guide with unilateral light extraction;

3 an enlarged section of a side emitting optical fiber as a light guide;

4 the end of a fiber bundle with light emission at break points of the individual optical fibers;

5 a second embodiment of the photocatalytic cleaning device according to the invention with plate-shaped light-guiding elements and

6 a section of an embodiment of the photocatalyst device according to the invention with a plurality of formed into a ball of optical fibers and a photocatalytic substance in the form of a loose particle composite.

According to the embodiment of 1 forms the photocatalyst device according to the invention consisting of a light-guiding element in the form of a plurality of optical fibers 10 , A standing with the optical fibers in light-conducting connection light source 12 and a photocatalytic substance (not shown) arranged on the optical fibers, namely Bi ₂ O ₃ and / or N-doped TiO ₂ and / or C-doped TiO ₂ and / or S-doped TiO ₂ and / or a binary bismuth metal oxide Compound, a photocatalytic cleaning device for cleaning a flowing through the optical fibers fluid. The fluid flow is indicated by the arrows 14 , The optical fibers 10 are in a cube-shaped reaction space 16 arranged in the form of a tangle. The reaction space 16 For example, it can be formed by a housing with an outlet and inlet opening for passing the fluid flow.

In 2 an embodiment of the photocatalyst device according to the invention is shown schematically in cross section, in which the light guide element is a one-sided emitting plate-shaped substrate 20 is. The substrate may be formed of a glass plate, preferably of borosilicate float glass or of a plate-shaped soda-lime glass substrate, or of one of the aforementioned plastics, into which one or more end faces 22 Light is coupled, marked by the arrow 24 , On one side face, the substrate faces 20 a roughened surface 26 on. Due to the roughened surface, depending on the degree of roughness, a certain proportion of the substance in the substrate 20 guided light emitted laterally, since at the roughness with statistical significance of the minimum angle at which total reflection takes place falls below. The side of the roughened surface of the substrate 20 is with the photocatalytic substance, shown as a regular arrangement of particles 28 , applied. The photocatalytic substance can actually be applied to a more or less uniform layer covering the entire surface by one of the abovementioned coating methods in particle form, preferably in the form of nanoparticles.

Notwithstanding the in 2 illustrated embodiment, both side surfaces of the substrate 20 roughened and coated with the photocatalytic substance.

In the embodiment according to 3 is a side-emitting step index fiber as a light-guiding element 30 intended. On average, it can be seen that these are a core 32 and a transparent and / or translucent jacket enclosing this circumference 34 having. A scattering of the light guided in the step index fiber to the side light emission occurs at scattering centers (not shown) between the cladding 34 and the core 32 instead of. On the outer circumference of the shell, the photocatalytic substance is arranged, again shown here as a uniform arrangement of particles 38 ,

In the embodiment according to 4 is a bundle on the left side 40 from several normal, ie not side-emitting, optical fibers 42 shown as a light-guiding element. On the right side is a section of one of these optical fibers 42 shown in an enlarged view. The coupled at one end of the fiber bundle light, represented by the arrow 44 , Occurs in this embodiment at the opposite front end at break points 46 the individual optical fibers 42 out. These breakages 46 are in the longitudinal direction of the fiber bundle 40 arranged at different positions, so that the light over a certain length of the fiber bundle 40 exits in the desired form. The breakages 46 have different surface structures, so that the light statistically on the plurality of optical fibers 42 from the end of the fiber bundle 40 is scattered in a large solid angle range. In this embodiment, it is sufficient if the photocatalytic substance is applied only in the region of this particular length section of the fiber bundle. For this purpose, the optical fibers can be coated with the end of the breakages individually or the entire bundle, for example, in a dipping process.

In 5 a second embodiment of a photocatalytic cleaning device according to the invention is shown in which a plurality of light-conducting plates arranged in parallel as the light-guiding element 50 are provided. These plates can be made of glass or plastic and roughened on one or both sides or be provided with scattering centers and be coated on this one or both sides with a photocatalytic substance of the type according to the invention. The light is from an artificial light source 52 generated with maximum radiation in the visible spectrum and a light-conducting cable 53 and a photoconductive manifold plate 54 on the plate-shaped light guide elements 50 distributed. The light enters the side of the roughened or provided with scattering surfaces surface of the plate-shaped light guide elements 50 aus and stimulates the applied there photocatalytic substance.

The stack of plate-shaped light guide elements 50 defines a reaction space 56 which may be bounded by a housing not shown here and provided with an inlet and an outlet opening. A fluid to be cleaned or decomposed is passed through the plate assembly, marked by the directional arrows 58 , The size of the plate-shaped light guide elements, ie their active (roughened and coated) surface, and their length, in particular in the flow direction is adapted to the flow rate and thus on the dwell or reaction time of the fluid flowing through in the reaction space such that the fullest possible implementation of the organic substance can take place by the catalytically excited reaction.

In 6 is a section of a tangle of one or more side emitting optical fibers 60 shown. Unlike in the example of 3 are the optical fibers 60 but not evenly coated with the catalytic substance along its outer peripheral surface. In the example of 6 is photocatalytic substance in the form of particles 62 on carrier particles 64 attached and this particle composite as a loose powder in the ball of optical fibers 60 embedded.

LIST OF REFERENCE NUMBERS

10

optical fiber

12

light source

14

fluid flow

16

reaction chamber

20

plate-shaped light guide

22

face

24

light coupling

26

roughened surface

28

photocatalytic coating

30

Side-emitting optical fiber

32

core

34

coat

38

photocatalytic coating

40

fiber bundles

42

optical fiber

44

light coupling

46

breaking points

50

plate-shaped light guide

52

light source

53

photoconductive cable

54

photoconductive distributor plate

56

reaction chamber

58

fluid flow

60

Side-emitting optical fiber

62

photocatalytic particles

64

carrier particles

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5564065 [0003]
• US 6324329 B1 [0004]
• EP 1008565 A1 [0005]
• US 6468428 B1 [0006]
• US Pat. No. 6,764,665 B1 [0007]
• US 6685889 B1 [0008]

Cited non-patent literature

• "SCHOTT Series on Glass and Glass Ceramics - Science, Technology and Applications", The Properties of Optical Glass (1995, 2nd, corr. Ed., 1998), Bach, Neuroth (Eds.) [0030]

Claims (24)

Photocatalyst device comprising a light-conducting element and a photocatalytic substance arranged on the light-guiding element, characterized in that the photocatalytic substance Bi ₂ O ₃ , and / or N-doped TiO ₂ and / or C-doped TiO ₂ and / or S-doped TiO ₂ and / or a bismuth metal oxide binary compound. A photocatalyst device according to claim 1, characterized in that the bismuth metal oxide binary compound is a compound of the group MBiO ₃ · xH ₂ O, where M = alkali and x ≥ 0, BiVO ₄ , Bi ₂ MoO ₆ and Bi ₂ WO ₆ is. Photocatalyst device according to Claim 1, characterized in that the photocatalytic substance has α-Bi ₂ O ₃ and / or β-Bi ₂ O ₃ . Photocatalyst device according to one of the preceding claims, characterized in that the light-guiding element comprises at least one optical fiber ( 10 . 42 ) having. Photocatalyst device according to claim 4, characterized in that the optical fiber ( 10 . 42 ) a side-emitting refractive index matched optical fiber ( 30 . 60 ), along the outer peripheral surface of which scattering centers and the photocatalytic substance are arranged. Photocatalyst device according to claim 5, characterized in that the scattering centers are formed by scattering particles on the outer peripheral surface. Photocatalyst device according to claim 5 or 6, characterized in that the scattering centers are embedded in a glass layer which surrounds the outer peripheral surface at least on a portion. Photocatalyst device according to claim 4, characterized in that the optical fiber ( 10 . 42 ) a side-emitting step index fiber having a core ( 32 ) enclosing transparent and / or translucent jacket ( 34 ), wherein scattering centers between the shell ( 34 ) and the core ( 32 ) and the photocatalytic substance on the shell ( 34 ) are arranged. Photocatalyst device according to claim 8, characterized in that the scattering centers by scattering particles on the outer peripheral surface of the core ( 32 ) are formed. Photocatalyst device according to claim 8 or 9, characterized in that the scattering centers are embedded in a glass layer which forms the core ( 32 ) surrounds at least a section. Photocatalyst device according to one of claims 9 to 9, characterized in that the scattering centers by inhomogeneities of the optical fiber material in the outer peripheral region of the core ( 32 ) are formed. Photocatalyst device according to one of claims 4 to 11, characterized in that the at least one optical fiber ( 10 . 42 ) is formed into a net, tissue or ball. Photocatalyst device according to claim 12, characterized in that the photocatalytic substance in the form of particles ( 62 ) on carrier particles ( 64 ) and this particle composite is embedded as a loose powder in the mesh, fabric or ball. Photocatalyst device according to one of claims 1 to 3, characterized in that the light-guiding element has a plate-shaped substrate. Photocatalyst device according to claim 14, characterized in that the substrate consists of soda lime or borosilicate float glass. Photocatalyst device according to one of the preceding claims, characterized in that the light-conducting element with particles ( 62 ) of the photocatalytic substance is coated. Photocatalyst device according to claim 16, characterized in that the particles ( 62 ) are applied to the light guide by means of a sol-gel process. Photocatalyst device according to one of the preceding claims, characterized in that the photocatalytic substance is arranged in the form of nanoparticles on the light-guiding element. Photocatalyst device according to one of the preceding claims, characterized in that the light-guiding element has a roughened surface. Photocatalyst device according to one of the preceding claims, characterized in that the light-guiding element has an outer surface, are arranged on the scattering centers or embedded in the scattering centers. Photocatalyst device according to one of the preceding claims, characterized in that the light-guiding element consists of a bundle of optical fibers ( 10 . 42 ), which in the longitudinal direction of the fiber bundle ( 40 ) at different position break points ( 46 ) exhibit. Photocatalyst device according to one of the preceding claims, characterized by an artificial light source with radiation maximum in the visible spectrum, which is in photoconductive connection with the light-guiding element. Photocatalyst device according to one of the preceding claims, characterized in that the artificial light source comprises at least one LED, incandescent lamp or gas discharge lamp. Photocatalyst device according to one of the preceding claims, characterized by means for collecting sunlight which are in photoconductive connection with the light-guiding element.

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