EP0704555A1 - Aluminium electrode - Google Patents
Aluminium electrode Download PDFInfo
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- EP0704555A1 EP0704555A1 EP95113648A EP95113648A EP0704555A1 EP 0704555 A1 EP0704555 A1 EP 0704555A1 EP 95113648 A EP95113648 A EP 95113648A EP 95113648 A EP95113648 A EP 95113648A EP 0704555 A1 EP0704555 A1 EP 0704555A1
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- aluminum foil
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- electromagnetic radiation
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- electrolyte bath
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/16—Polishing
- C25F3/22—Polishing of heavy metals
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/02—Etching
- C25F3/04—Etching of light metals
Definitions
- the invention relates to the use of an aluminum foil for the chemical reduction of liquid and / or gaseous components such as CO2, and / or as a detector for electromagnetic radiation, e.g. in the UV range, using the photo emission process (photo effect).
- the photo effect is the removal of electrons from the inside of a solid through its surface into the surrounding medium, air or vacuum, by irradiation with electromagnetic radiation such as light, X-rays or ⁇ -rays.
- electromagnetic radiation such as light, X-rays or ⁇ -rays.
- an insulated metal plate which is irradiated with electromagnetic radiation, for example in the UV range, charges up to an electrical potential if it is ensured that the released electrons are sucked off by an electric field.
- the number of photoelectrons or the current strength of the photocurrent formed by the photoelectrons is proportional to the frequency of the absorbed light intensity when exposed to monochromatic electromagnetic radiation.
- the kinetic energy of the released photoelectrons depends on the frequency of the incident electromagnetic radiation and on the so-called work function of the irradiated metal.
- the invention proposes the use of an aluminum foil for the chemical reduction of liquid and / or gaseous Components such as CO2 and / or as a detector for electromagnetic radiation, for example in the UV range, using the photo effect before.
- This goal is essentially achieved by subjecting the aluminum foil to a surface treatment to increase the surface roughness, exposing the roughened aluminum foil as a negative electrode to a potential voltage in an electrolyte bath which may contain the reducing liquid and / or gaseous components, and exposing the roughened to a potential voltage subjecting aluminum foil in the electrolytic bath to a photoemission process, for example using the electromagnetic radiation to be detected.
- An aluminum foil prepared in this way is particularly suitable for the chemical reduction of liquid and / or gaseous components and / or as a detector for electromagnetic radiation, since it has surprisingly been shown that a surprisingly high quantum yield is obtained even when relatively long-wave electromagnetic radiation acts on the aluminum foil is achievable.
- the quantum yield is defined as the ratio of the number of emitted electrons to the number of incident photons. Liquid components can be easily reduced by means of the strongly reducing emitted photoelectrons.
- the aluminum foil is roughened mechanically, for example by sandblasting, by electromechanical polishing and / or by electromechanical etching. These measures have a positive influence on the quantum yield.
- the surface of the aluminum foil is provided with a roughness corresponding to a roughness factor between 1.75 and 3.
- An aluminum foil with a capacitance between 0.5 and 2.0 ⁇ F cm ⁇ 2 (at + 8 V (MSE)) is advantageously used.
- the surface of an untreated aluminum foil is enlarged by a surface treatment, in particular by electromechanical etching or the like, by a factor (surface enlargement factor (SEF) between approximately 10 and approximately 40.
- SEF surface enlargement factor
- the surface of the aluminum foil is treated with perchloric acid and / or ethanol to enlarge the surface.
- the surface in particular for blasting, can be treated with aluminum particles with a grain size or an average diameter between 1 ⁇ m and approximately 45 ⁇ m.
- solutions with the exclusion of aggressive anions e.g. Halogens used.
- the electrolyte bath advantageously has a pH between about 5 and about 10.
- electrolytic bath also includes gaseous components, in particular CO2 and / or N2, which can also be reduced by means of the aluminum foil using the photo effect.
- the amount of potential voltage that can be applied to the aluminum foil is preferably set to values below approximately 2 volts. This measure advantageously allows the work function to be overcome by the photoelectrons when exiting the aluminum foil to be reduced. As a result, there is also the possibility of using long-wave electromagnetic radiation to release the photoelectrons from the aluminum foil, in which case a large number of suitable electromagnetic radiation sources can be used.
- electromagnetic radiation with a wavelength ⁇ of approximately 300 nm was advantageously used.
- a liquid electrolyte bath a potential voltage of approximately 1.8 to 1.9 volts and an electromagnetic radiation with a wavelength ⁇ of approximately 300 nm are used.
- a high quantum yield of approximately 2% to approximately 4 was obtained under these conditions % reached.
- the aluminum foil is advantageously suitable for use as a detector for electromagnetic radiation, wherein the aluminum foil is exposed to electromagnetic radiation, in particular UV radiation, and the photocurrent is measured. Because of the very high quantum yield, a particularly sensitive measuring instrument or a sensitive detector for electromagnetic radiation is therefore made available.
- an aluminum foil for, for example, the chemical reduction of liquid or gaseous components or as a detector for electromagnetic radiation
- the aluminum foil is subjected to a surface treatment in order to enlarge the effective surface or the surface roughness.
- the aluminum foil is then introduced as a negative electrode into an electrolyte bath and a potential voltage is applied. If the aluminum foil in the electrolyte bath is exposed to electromagnetic radiation, preferably with wavelengths in the UV range, an emission of photoelectrons from the aluminum foil can be observed directly into the electrolyte bath, provided the aluminum foil is exposed to a suitable surface treatment and placed on a suitable potential voltage and has been exposed to electromagnetic radiation of a suitable wavelength.
- the energy threshold E th (eV) varies as a function of the applied potential voltage.
- the main difference to the photo effect on a metal / vacuum interface results from the fact that the applied potential voltage leads to polarization of the metal / solution interface and the function of the work function (W Me / Sol ) of a metal introduced into a solution influenced essentially linearly.
- a further reduction in the work function at the aluminum / electrolyte bath interface could not be measured, since a strong hydrogen evolution at potential voltages more negative than -1.95 volts (based on MSE) starts in the electrolyte bath.
- an increase in the photocurrent can be achieved due to a suitable surface treatment of the metal. It is therefore appropriate to roughen the aluminum foil mechanically, for example by sandblasting, by electromechanical polishing or by electrochemical etching or a combination of these processes.
- electropolishing of the surface of the aluminum foil by means of perchloric acid and / or ethanol has proven itself, the surface of the aluminum foil being mechanically polished in a subsequent step with aluminum particles with a diameter between approximately 1 ⁇ m and approximately 45 ⁇ m.
- the surface of the aluminum foil has a roughness corresponding to a roughness factor between 1.75 and 3. These roughness factors are determined by measuring the capacity of the aluminum foil at 9 volts (MSE). With the surface treatment methods shown, the surface of the aluminum foil was increased by a factor (surface enlargement factor SEF) between approximately 10 and approximately 40.
- SEF surface enlargement factor
- the electrolytic bath consists of solutions that do not contain aggressive anions, e.g. Halogens.
- the pH of the electrolyte bath is in a range between about 5 and about 10. Because of the hydrogen evolution mentioned above in the electrolyte bath, the magnitude of the potential voltage is set to values below about 2 volts.
- this system can also be used to reduce very stable gaseous substances such as CO2 or N2.
- Another type of use of the system described is the use of the aluminum / solution interface as a detector for electromagnetic radiation, in particular in the UV range, in which a high quantum yield can be achieved.
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Abstract
Description
Die Erfindung betrifft die Verwendung einer Aluminiumfolie für die chemische Reduktion flüssiger und/oder gasförmiger Komponenten wie CO₂, und/oder als Detektor für elektromagnetische Strahlung, z.B. im UV-Bereich, unter Ausnutzung des Fotoemissionsprozesses (Fotoeffekt).The invention relates to the use of an aluminum foil for the chemical reduction of liquid and / or gaseous components such as CO₂, and / or as a detector for electromagnetic radiation, e.g. in the UV range, using the photo emission process (photo effect).
Unter dem Fotoeffekt versteht man das Herauslösen von Elektronen aus dem Inneren eines Festkörpers durch seine Oberfläche hindurch in das umgebende Medium, Luft oder Vakuum, durch Einstrahlung elektromagnetischer Strahlung, wie Licht-, Röntgen- oder γ-Strahlen. Bei diesem, sogenannten äußeren Fotoeffekt lädt sich eine mit elektromagnetischer Strahlung, bspw. im UV-Bereich bestrahlte, isoliert aufgehängte-Metallplatte auf ein elektrisches Potential auf, wenn dafür gesorgt wird, daß die herausgelösten Elektronen durch ein elektrisches Feld abgesaugt werden. Die Anzahl der Fotoelektronen bzw. die Strömstärke des durch die Fotoelektronen gebildeten Fotostroms ist bei Einwirkung monochromatischer elektromagnetischer Strahlung der Frequenz der absorbierten Lichtintensität proportional. Die kinetische Energie der ausgelösten Fotoelektronen hängt von der Frequenz der einfallenden elektromagnetischen Strahlung und von der sogenannten Austrittsarbeit des bestrahlten Metalls ab.The photo effect is the removal of electrons from the inside of a solid through its surface into the surrounding medium, air or vacuum, by irradiation with electromagnetic radiation such as light, X-rays or γ-rays. In this so-called external photo effect, an insulated metal plate which is irradiated with electromagnetic radiation, for example in the UV range, charges up to an electrical potential if it is ensured that the released electrons are sucked off by an electric field. The number of photoelectrons or the current strength of the photocurrent formed by the photoelectrons is proportional to the frequency of the absorbed light intensity when exposed to monochromatic electromagnetic radiation. The kinetic energy of the released photoelectrons depends on the frequency of the incident electromagnetic radiation and on the so-called work function of the irradiated metal.
Die Erfindung schlägt die Verwendung einer Aluminiumfolie für die chemische Reduktion flüssiger und/oder gasförmiger Komponenten wie CO₂ und/oder als Detektor für elekromagnetische Strahlungen, z.B. im UV-Bereich, unter Ausnutzung des Fotoeffektes vor. Dieses Ziel wird im wesentlichen dadurch erreicht, daß man die Aluminiumfolie einer Oberflächenbehandlung zur Vergrößerung der Oberflächenrauhigkeit aussetzt, die aufgerauhte Aluminiumfolie als negative Elektrode in einem ggf. die reduzierenden flüssigen und/oder gasförmigen Komponenten enthaltenen Elektrolytbad einer Potentialspannung aussetzt, und die aufgerauhte mit einer Potentialspannung in dem Elektrolytbad beaufschlagte Aluminiumfolie einem Fotoemissionsprozeß, z.B. unter Verwendung der nachzuweisenden elektromagnetischen Strahlung, unterwirft. Eine solchermaßen präparierte Aluminiumfolie eignet sich in besonderer Weise für die chemische Reduktion flüssiger und/oder gasförmiger Komponenten und/oder als Detektor für elektromagnetische Strahlung, da sich überraschenderweise zeigt, daß bereits bei einer Einwirkung von relativ langwelliger elektromagnetischer Strahlung auf die Aluminiumfolie eine überraschend hohe Quantenausbeute erzielbar ist. Die Quantenausbeute ist definiert als das Verhältnis der Anzahl der emittierten Elektronen bezogen auf die Anzahl der einfallenden Fotonen. Mittels der stark reduzierend wirkenden emittierten Fotoelektronen können flüssige Komponenten ohne weiteres reduziert werden. Es besteht darüber hinaus die Möglichkeit, mit einer derartigen Aluminiumfolie sehr stabile gasförmige Substanzen wie CO₂ oder N₂ mittels der aus der Aluminiumfolie austretenden Fotoelektronen zu reduzieren.The invention proposes the use of an aluminum foil for the chemical reduction of liquid and / or gaseous Components such as CO₂ and / or as a detector for electromagnetic radiation, for example in the UV range, using the photo effect before. This goal is essentially achieved by subjecting the aluminum foil to a surface treatment to increase the surface roughness, exposing the roughened aluminum foil as a negative electrode to a potential voltage in an electrolyte bath which may contain the reducing liquid and / or gaseous components, and exposing the roughened to a potential voltage subjecting aluminum foil in the electrolytic bath to a photoemission process, for example using the electromagnetic radiation to be detected. An aluminum foil prepared in this way is particularly suitable for the chemical reduction of liquid and / or gaseous components and / or as a detector for electromagnetic radiation, since it has surprisingly been shown that a surprisingly high quantum yield is obtained even when relatively long-wave electromagnetic radiation acts on the aluminum foil is achievable. The quantum yield is defined as the ratio of the number of emitted electrons to the number of incident photons. Liquid components can be easily reduced by means of the strongly reducing emitted photoelectrons. There is also the possibility of using such an aluminum foil to reduce very stable gaseous substances such as CO₂ or N₂ by means of the photoelectrons emerging from the aluminum foil.
Nach einer bevorzugten Ausführungsform der Erfindung rauht man die Aluminiumfolie mechanisch, z.B. durch Sandstrahlen, durch elektromechanisches Polieren und/oder durch elektromechanisches Ätzen auf. Durch diese Maßnahmen wird die Quantenausbeute positiv beeinflußt.According to a preferred embodiment of the invention, the aluminum foil is roughened mechanically, for example by sandblasting, by electromechanical polishing and / or by electromechanical etching. These measures have a positive influence on the quantum yield.
Nach einer weiteren Ausführungsform der Erfindung versieht man die Oberfläche der Aluminiumfolie mit einer Rauhigkeit entspechend einem Rauhigkeitsfaktor zwischen 1,75 und 3.According to a further embodiment of the invention, the surface of the aluminum foil is provided with a roughness corresponding to a roughness factor between 1.75 and 3.
Von Vorteil wird eine Aluminiumfolie mit einer Kapazität zwischen 0,5 und 2,0 µF cm⁻² (bei + 8 V (MSE) verwendet.An aluminum foil with a capacitance between 0.5 and 2.0 µF cm⁻² (at + 8 V (MSE)) is advantageously used.
Nach einer anderen vorteilhaften Weiterbildung der Erfindung vergrößert man die Oberfläche einer unbehandelten Aluminiumfolie durch eine Oberflächenbehandlung, insbesondere durch elektromechanisches Ätzen oder dgl., um einen Faktor (Oberflächenvergrößerungsfaktor (SEF) zwischen etwa 10 und etwa 40.According to another advantageous development of the invention, the surface of an untreated aluminum foil is enlarged by a surface treatment, in particular by electromechanical etching or the like, by a factor (surface enlargement factor (SEF) between approximately 10 and approximately 40.
Es hat sich als vorteilhaft erwiesen, daß die Oberfläche der Aluminiumfolie mit Perchlorsäure und/oder Ethanol zur Vergrößerung der Oberfläche behandelt wird.It has proven to be advantageous that the surface of the aluminum foil is treated with perchloric acid and / or ethanol to enlarge the surface.
Alternativ oder in Kombination zu dieser Oberflächenbehandlung der Aluminiumfolie mit Perchlorsäure und/oder Ethanol kann die Oberfläche, insbesondere zum strahlen, mit Aluminiumpartikeln einer Korngröße bzw. eines mittleren Durchmessers zwischen 1 µm und etwa 45 µm behandelt werden.As an alternative or in combination with this surface treatment of the aluminum foil with perchloric acid and / or ethanol, the surface, in particular for blasting, can be treated with aluminum particles with a grain size or an average diameter between 1 μm and approximately 45 μm.
Von Vorteil werden als Elektrolytbad Lösungen unter Ausschluß aggressiver Anionen, wie z.B. Halogene, verwendet.As an electrolyte bath, solutions with the exclusion of aggressive anions, e.g. Halogens used.
Nach einem weiteren Merkmal der Erfindung weist das Elektrolytbad von Vorteil einen pH-Wert zwischen etwa 5 und etwa 10 auf.According to a further feature of the invention, the electrolyte bath advantageously has a pH between about 5 and about 10.
Im Rahmen dieser Erfindung werden unter dem Begriff Elektrolytbad auch gasförmige Komponenten, insbesondere CO₂ und/oder N₂ verstanden, die mittels der Aluminiumfolie unter Ausnutzung des Fotoeffekts ebenfalls reduzierbar sind.In the context of this invention, the term electrolytic bath also includes gaseous components, in particular CO₂ and / or N₂, which can also be reduced by means of the aluminum foil using the photo effect.
Der Betrag der Potentialspannung, mit der die Aluminiumfolie beaufschlagbar ist, wird bevorzugt auf Werte unter etwa 2 Volt eingestellt. Durch diese Maßnahme läßt sich in vorteilhafter Weise die von den Fotoelektronen beim Austreten aus der Aluminiumfolie zu überwindende Austrittsarbeit senken. Infolge dessen besteht auch die Möglichkeit, langwellige elektromagnetische Strahlung zum Auslösen der Fotoelektronen aus der Aluminiumfolie einzusetzen, wobei in diesem Fall auf eine Vielzahl geeigneter elektromagnetischer Strahlungsquellen zurückgegriffen werden kann.The amount of potential voltage that can be applied to the aluminum foil is preferably set to values below approximately 2 volts. This measure advantageously allows the work function to be overcome by the photoelectrons when exiting the aluminum foil to be reduced. As a result, there is also the possibility of using long-wave electromagnetic radiation to release the photoelectrons from the aluminum foil, in which case a large number of suitable electromagnetic radiation sources can be used.
Als besonders vorteilhaft hat sich die Verwendung elektromagnetischer Strahlung im UV-Bereich erwiesen.The use of electromagnetic radiation in the UV range has proven to be particularly advantageous.
In einem speziellen Anwendungsfall wurde elektromagnetische Strahlung einer Wellenlänge λ von etwa 300 nm mit Vorteil verwendet.In a special application, electromagnetic radiation with a wavelength λ of approximately 300 nm was advantageously used.
Nach einer speziellen Ausgestaltung verwendet man ein flüssiges Elektrolytbad, eine Potentialspannung von etwa 1,8 bis 1,9 Volt und eine elektromagnetische Strahlung mit einer Wellenlänge λ von etwa 300 nm. Unter diesen Bedingungen wurde überraschenderweise eine hohe Quantenausbeute von etwa 2% bis etwa 4% erreicht.According to a special embodiment, a liquid electrolyte bath, a potential voltage of approximately 1.8 to 1.9 volts and an electromagnetic radiation with a wavelength λ of approximately 300 nm are used. Surprisingly, a high quantum yield of approximately 2% to approximately 4 was obtained under these conditions % reached.
Aufgrund der hohen Quantenausbeute eignet sich die Aluminiumfolie mit Vorteil für die Verwendung als Detektor für elektromagnetische Strahlung, wobei man die Aluminiumfolie mit elektromagnetischer Strahlung, insbesondere UV-Strahlung, beaufschlagt und den Fotostrom meßtechnisch erfaßt. Aufgrund der recht hohen Quantenausbeute wird daher ein besonders empfindliches Meßinstrument bzw. ein empfindlicher Detektor für elektromagnetiche Strahlung zur Verfügung gestellt.Because of the high quantum yield, the aluminum foil is advantageously suitable for use as a detector for electromagnetic radiation, wherein the aluminum foil is exposed to electromagnetic radiation, in particular UV radiation, and the photocurrent is measured. Because of the very high quantum yield, a particularly sensitive measuring instrument or a sensitive detector for electromagnetic radiation is therefore made available.
Weitere Ziele, Merkmale, Vorteile und Anwendungsmöglichkeiten der vorliegenden Erfindung ergeben sich aus der nachfolgenden Beschreibung von Ausführungsbeispielen. Dabei bilden alle Merkmale für sich oder in beliebiger Kombination den Gegenstand der Erfindung, auch unabhängig in ihrer Zusammenfassung in den Ansprüchen oder deren Rückbeziehung.Further objectives, features, advantages and possible uses of the present invention result from the following description of exemplary embodiments. All features form the subject matter of the invention individually or in any combination, also independently in their summary in the claims or their relationship.
Zur Verwendung einer Aluminiumfolie für bspw. die chemische Reduktion flüssiger oder gasförmiger Komponenten oder als Detektor für elektromagnetische Strahlung wird die Aluminiumfolie einer Oberflächenbehandlung zur Vergrößerung der wirksamen Oberfläche bzw. der Oberflächenrauhigkeit ausgesetzt. Anchließend wird die Aluminiumfolie als negative Elektrode in ein Elektrolytbad eingebracht und mit einer Potentialspannung beaufschlagt. Setzt man die Aluminiumfolie in dem Elektrolytbad einer elektromagnetischen Strahlung, vorzugsweise mit Wellenlängen im UV-Bereich, aus, so ist eine Emission von Fotoelektronen aus der Aluminiumfolie direkt in das Elektrolytbad zu beobachten, sofern die Aluminiumfolie einer geeigneten Oberflächenbehandlung ausgesetzt, auf eine geeignete Potentialspannung gelegt und mit einer elektromagnetischen Strahlung geeigneter Wellenlänge beaufschlagt worden ist. Dieses Phänomen der Emission von Fotoelektronen aus der Aluminiumfolie direkt in das Elekrolytbad weist einige Gemeinsamkeiten mit dem Fotoeffekt auf, wie er an der Grenzschicht zwischen einem Metall und dem Vakuum beim Auftreffen von elektromagnetischer Strahlung auf die Metallfläche nachweisbar ist. Allerdings weist die photoninduzierte Emission von Elektronen aus einer Aluminiumfolie, die in ein Elektrolytbad eingetaucht ist, auch folgende unterschiedlichen Aspekte auf:In order to use an aluminum foil for, for example, the chemical reduction of liquid or gaseous components or as a detector for electromagnetic radiation, the aluminum foil is subjected to a surface treatment in order to enlarge the effective surface or the surface roughness. The aluminum foil is then introduced as a negative electrode into an electrolyte bath and a potential voltage is applied. If the aluminum foil in the electrolyte bath is exposed to electromagnetic radiation, preferably with wavelengths in the UV range, an emission of photoelectrons from the aluminum foil can be observed directly into the electrolyte bath, provided the aluminum foil is exposed to a suitable surface treatment and placed on a suitable potential voltage and has been exposed to electromagnetic radiation of a suitable wavelength. This phenomenon of the emission of photoelectrons from the aluminum foil directly into the electrolytic bath has some similarities with the photo effect, as can be detected at the boundary layer between a metal and the vacuum when electromagnetic radiation hits the metal surface. However, the photon-induced emission of electrons from an aluminum foil immersed in an electrolyte bath also has the following different aspects:
An der Grenzschicht zwischen der Metalloberfläche und der Elekrolytlösung baut sich eine elektrische Doppelschicht auf, an der die ganze Potentialspannung, mit der die Aluminiumfolie beaufschlagt wird, abfällt. Hieraus folgt, daß eine weitere Variable die Fotoemission der Elektronen aus der Aluminiumschicht in das Elektrolytbad beeinflußt. Im Vergleich zum Fotoeffekt an einer Metall/Vakuum-Grenzschicht ändert sich der Energieschwellwert für die Fotoemission der Elektronen gemäß der Gleichung
Während die Emission eines Fotoelektrons aus einem Metall in das Vakuum als rein physikalisches Phänomen interpretiert werden kann, ohne daß es im Anschluß an die Emission der Elektronen zu chemischen Reaktionen kommt, ist dies im Falle einer Metall/Lösung-Grenzfläche anders. Dann gelangen nämlich die aufgrund des Fotoeffekts emittierten Elektronen in die Lösung bzw. das Elektrolytbad und setzen eine Reihe chemischer Reaktionen in Gang. Als Endresultat findet eine chemische Reduktion der flüssigen oder gasförmigen Komponenten, die in dem Elektrolytbad enthalten sind, statt.While the emission of a photoelectron from a metal into the vacuum can be interpreted as a purely physical phenomenon without chemical reactions following the emission of the electrons, this is different in the case of a metal / solution interface. Then the electrons emitted due to the photo effect get into the solution or the electrolyte bath and initiate a series of chemical reactions. The end result is a chemical reduction of the liquid or gaseous components contained in the electrolyte bath.
Eine Abschätzung der Intensität des Fotostroms an einer Metall/Lösung-Grenzfläche ist relativ schwierig. Unter Außerachtlassung von Oberflächenvergrößerungseffekten, die gewöhnlich auf die Oberflächenrauhigkeit und/oder an der Oberfläche erzeugte Elektronen auf Plasmaschwingungen des Metalls zurückzuführen sind, ergeben Modellberechnungen Quantenausbeuten in der Größenordnung von 10⁻⁵ bis 10⁻⁴ für unterschiedliche Metall/Elektrolyt-Oberflächen.It is relatively difficult to estimate the intensity of the photocurrent at a metal / solution interface. Under Disregarding surface enlargement effects, which are usually due to the surface roughness and / or electrons generated on the surface due to plasma vibrations of the metal, model calculations give quantum yields in the order of 10⁻⁵ to 10⁻⁴ for different metal / electrolyte surfaces.
Im Spezialfall einer Aluminium/Vakuum-Grenzfläche konnten Quantenausbeuten von etwa 4% bei einer Energie der eingestrahlten elektromagnetischen Strahlung nahe der Plasmafrequenz (hγ = 10 eV) gemessen werden. Andererseits konnte für eine Aluminium/Elektrolyt-Grenzfläche ein Emissionsgrenzwert nahe hγ = 2 eV ermittelt werden, der auf einer Reduzierung der metallischen Austrittsarbeit aufgrund der angelegten potentialen Spannung zurückzuführen ist. Die Austrittsarbeit für die Grenzschicht/Aluminium/Elektrolyt liegt bei etwa h γ = 4,15 eV. Eine weitere Reduzierung der Austrittsarbeit an der Grenzschicht Aluminium/Elektrolytbad konnte nicht gemessen werden, da eine starke Wasserstoffentwicklung bei Potentialspannungen negativer als -1,95 Volt (bezogen auf MSE) in dem Elektrolytbad einsetzt.In the special case of an aluminum / vacuum interface, quantum yields of about 4% could be measured with an energy of the incident electromagnetic radiation close to the plasma frequency (hγ = 10 eV). On the other hand, an emission limit value close to hγ = 2 eV could be determined for an aluminum / electrolyte interface, which is due to a reduction in the metal work function due to the applied potential voltage. The work function for the boundary layer / aluminum / electrolyte is approximately h γ = 4.15 eV. A further reduction in the work function at the aluminum / electrolyte bath interface could not be measured, since a strong hydrogen evolution at potential voltages more negative than -1.95 volts (based on MSE) starts in the electrolyte bath.
Wie aus der Tabelle am Ende der Beschreibung zu entnehmen ist, kann eine Verstärkung des Fotostroms aufgrund einer geeigneten Oberflächenbehandlung des Metalls erreicht werden. So ist es angezeigt, die Aluminiumfolie mechanisch, z.B. durch Sandstrahlen, durch elektromechanisches Polieren oder durch elektrochemisches Ätzen oder einer Kombination dieser Verfahren aufzurauhen. Insbesondere hat sich ein Elektropolieren der Oberfläche der Aluminiumfolie mittels Perchlorsäure und/oder Ethanol bewährt, wobei die Oberfläche der Aluminiumfolie in einem anschließenden Schritt mit Aluminiumpartiklen eines Durchmessers zwischen etwa 1 µm und etwa 45 µm mechanisch poliert wird. Die Oberfläche der Aluminiumfolie weist eine Rauhigkeit entsprechend einem Rauhigkeitsfaktor zwischen 1,75 und 3 auf. Diese Rauhigkeitsfaktoren werden über eine Messung der Kapazität der Aluminiumfolie bei 9 Volt (MSE) ermittelt. Mit den dargestellten Oberflächenbehandlungsmethoden wurde die Oberfläche der Aluminiumfolie um einen Faktor (Oberflächenvergrößerungsfaktor SEF) zwischen etwa 10 und etwa 40 erhöht.As can be seen from the table at the end of the description, an increase in the photocurrent can be achieved due to a suitable surface treatment of the metal. It is therefore appropriate to roughen the aluminum foil mechanically, for example by sandblasting, by electromechanical polishing or by electrochemical etching or a combination of these processes. In particular, electropolishing of the surface of the aluminum foil by means of perchloric acid and / or ethanol has proven itself, the surface of the aluminum foil being mechanically polished in a subsequent step with aluminum particles with a diameter between approximately 1 μm and approximately 45 μm. The surface of the aluminum foil has a roughness corresponding to a roughness factor between 1.75 and 3. These roughness factors are determined by measuring the capacity of the aluminum foil at 9 volts (MSE). With the surface treatment methods shown, the surface of the aluminum foil was increased by a factor (surface enlargement factor SEF) between approximately 10 and approximately 40.
Das Elektrolytbad besteht aus solchen Lösungen, die keine aggressiven Anionen, wie z.B. Halogene, aufweisen. Der pH-Wert des Elektrolytbades liegt in einem Bereich zwischen etwa 5 und etwa 10. Aufgrund der oben erwähnten Wasserstoffentwicklung in dem Elekrolytbad wird der Betrag der Potentialspannung auf Werte unter etwa 2 Volt eingestellt. Bei der eingestrahlten elektromagnetischen Strahlung handelt es sich um Wellenlängen im UV-Bereich, insbesondere wurde Strahlung einer Wellenlänge von λ von etwa 300 nm eingesetzt. Dies entspricht einer Fotonenergie von hγ = 4 eV. Unter diesen Bedingungen konnte im Dauerzustand, also im eingeschwungenen Zustand des Systems, eine Quantenausbeute von ewa 2% bis etwa 4% erzielt werden.The electrolytic bath consists of solutions that do not contain aggressive anions, e.g. Halogens. The pH of the electrolyte bath is in a range between about 5 and about 10. Because of the hydrogen evolution mentioned above in the electrolyte bath, the magnitude of the potential voltage is set to values below about 2 volts. The incident electromagnetic radiation is wavelengths in the UV range, in particular radiation with a wavelength of λ of approximately 300 nm was used. This corresponds to a photon energy of hγ = 4 eV. Under these conditions, a quantum yield of approximately 2% to approximately 4% could be achieved in the permanent state, i.e. in the steady state of the system.
Berücksichtigt man die äußerst starke reduzierende Wirkung der emittierten Fotoelektronen, kann mit diesem System auch eine Reduzierung sehr stabiler gasförmiger Substanzen, wie CO₂ oder N₂ erreicht werden. Eine weitere Art der Verwendung des beschriebenen Systems besteht in dem Einsatz der Aluminium/Lösung-Grenzfläche als Detektor für elektromagnetische Strahlung insbesondere im UV-Bereich, in dem eine hohe Quantanausbeute erzielbar ist.
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DE4434557A DE4434557C2 (en) | 1994-09-28 | 1994-09-28 | Use an aluminum foil |
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AUPR099500A0 (en) * | 2000-10-25 | 2000-11-16 | Sustainable Technologies International Pty Ltd | Uv sensors and arrays and methods to manufacture thereof |
FR2936057B1 (en) * | 2008-09-17 | 2010-10-15 | Commissariat Energie Atomique | METHOD FOR CHARACTERIZING DIELECTRIC LAYERS BY ULTRAVIOLET PHOTO-EMISSION SPECTROSCOPY |
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DE381725C (en) * | 1923-09-24 | Licht Therapie G M B H | Device for measuring the intensity of ultraviolet radiation | |
US3628017A (en) * | 1970-06-18 | 1971-12-14 | Itek Corp | Ultraviolet light-sensitive cell using a substantially chemically unchanged semiconductor electrode in an electrolyte |
US4107008A (en) * | 1975-06-16 | 1978-08-15 | Beeston Company Limited | Electrolysis method for producing hydrogen and oxygen |
JPS5610219A (en) * | 1979-07-04 | 1981-02-02 | Matsushita Electric Ind Co Ltd | Ultraviolet integral detecting element and ultraviolet integral detector |
US4481091A (en) * | 1981-02-17 | 1984-11-06 | At&T Bell Laboratories | Chemical processing using electromagnetic field enhancement |
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USRE19218E (en) * | 1934-06-19 | Light-sensitive device | ||
US2064260A (en) * | 1930-03-08 | 1936-12-15 | Kurt Adamczick And Willy List | Method and apparatus for synthesizing nitrogen compounds |
JPS56138221A (en) * | 1980-03-31 | 1981-10-28 | Matsushita Electric Ind Co Ltd | Ultraviolet ray detecting element |
DE3829541A1 (en) * | 1987-09-03 | 1989-03-16 | Ricoh Kk | LEAF-SHAPED ELECTRODE, METHOD FOR PRODUCING THE SAME AND SECONDARY BATTERY CONTAINING THIS |
SU1711062A1 (en) * | 1989-01-12 | 1992-02-07 | Институт теплофизики СО АН СССР | Method of revealing aluminum surface structure defects |
JP2627563B2 (en) * | 1989-09-18 | 1997-07-09 | 富士写真フイルム株式会社 | Method for producing support for photosensitive lithographic printing plate |
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1994
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- 1995-01-14 DE DE29500544U patent/DE29500544U1/en not_active Expired - Lifetime
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Publication number | Priority date | Publication date | Assignee | Title |
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DE381725C (en) * | 1923-09-24 | Licht Therapie G M B H | Device for measuring the intensity of ultraviolet radiation | |
US3628017A (en) * | 1970-06-18 | 1971-12-14 | Itek Corp | Ultraviolet light-sensitive cell using a substantially chemically unchanged semiconductor electrode in an electrolyte |
US4107008A (en) * | 1975-06-16 | 1978-08-15 | Beeston Company Limited | Electrolysis method for producing hydrogen and oxygen |
JPS5610219A (en) * | 1979-07-04 | 1981-02-02 | Matsushita Electric Ind Co Ltd | Ultraviolet integral detecting element and ultraviolet integral detector |
US4481091A (en) * | 1981-02-17 | 1984-11-06 | At&T Bell Laboratories | Chemical processing using electromagnetic field enhancement |
Non-Patent Citations (1)
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PATENT ABSTRACTS OF JAPAN vol. 5, no. 56 (P - 57)<728> 17 April 1981 (1981-04-17) * |
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DE4434557A1 (en) | 1996-04-04 |
DE59500977D1 (en) | 1997-12-18 |
DE4434557C2 (en) | 2000-03-09 |
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