Optical optimisation for a photoelectrochemical reactor

Abstract

The invention relates to a facility comprising: - a solar photoelectrochemical reactor (1) comprising: a photoanode (PA) and a photocathode (PC) which are sensitive to solar radiation (RS); first and second walls (P1, P2) which are transparent to solar radiation (RS) and face the photoanode (PA) and the photocathode (PC), respectively; - an optical system arranged outside the solar photoelectrochemical reactor (1) comprising first and second reflectors (R1, R2) designed to reflect, respectively: a first spectral range of incident solar radiation (RS) toward the first wall (P1) and a second spectral range of incident solar radiation (RS), different from the first spectral range, toward the second wall (P2).

Description

[0001] OPTIMIZATION OF AN OPTIMIZATION OF A PHOTOELECTROCHEMICAL REACTOR

[0002] Technical field

[0003] The invention relates to the technical field of photoelectrochemical reactors.

[0004] The invention finds its application in particular in the dissociation of water (“water splitting” in English) for the production of dihydrogen H2, the production of solar fuels from water H2O and carbon dioxide CO2.

[0005] State of the art

[0006] A photoelectrochemical cell known from the state of the art, in particular from document EP 2 737 941 A1, comprises a photoanode and a photocathode, sensitive to solar radiation. The photoanode comprises a photocatalytic layer made of titanium dioxide TiO2, while the photocathode comprises a photocatalytic layer made of copper oxide Cu2O.

[0007] Such a state-of-the-art photoelectrochemical cell is not entirely satisfactory in terms of efficiency (or yield) since titanium dioxide TiO2 absorbs in the ultraviolet (wavelength less than 400 nm) and ultraviolet radiation only represents about 3% of the electromagnetic energy of the sun.

[0008] Much research is aimed at broadening the spectral response band of the photocatalytic layer of titanium dioxide TiO2 of the photoanode, for example by using suitable doping (e.g. nitrogen), by band engineering, by forming heterojunctions, by incorporating metal nanoparticles for surface plasmon resonance, by using co-catalysts, etc. Such state-of-the-art solutions are generally still at the research stage, and significantly complicate the manufacturing of the photoelectrochemical cell.

[0009] Furthermore, infrared radiation represents the majority (around 45%) of the electromagnetic energy of the sun, and leads to a massive transfer of heat to the photoelectrochemical cell which is likely to degrade over time.

[0010] Statement of the invention

[0011] The invention aims to remedy all or part of the aforementioned drawbacks. To this end, the invention relates to an installation, comprising:

[0012] - a solar photoelectrochemical reactor, comprising: a photoanode and a photocathode, sensitive to solar radiation; first and second walls, transparent to solar radiation, facing the photoanode and the photocathode respectively;

[0013] - an optical system, arranged outside the solar photoelectrochemical reactor, and comprising first and second reflectors, designed to respectively reflect: a first spectral domain of incident solar radiation towards the first wall, a second spectral domain of incident solar radiation, different from the first spectral domain, towards the second wall.

[0014] Thus, such an installation according to the invention makes it possible to differentiate the solar radiation received by the photoanode and the solar radiation received by the photocathode, thanks to an optical system arranged outside the photoelectrochemical reactor. Indeed, the solar radiation received by the photoanode has been spectrally filtered by the first reflector while the solar radiation received by the photocathode has been spectrally filtered by the second reflector. This differentiated spectral filtering for the photoanode and for the photocathode makes it possible to envisage an increase in the efficiency of the photoelectrochemical reactor by adjusting the first and second spectral domains respectively to the nature of the photoanode and the photocathode. This differentiated spectral filtering makes it possible to overcome the complex solutions of the state of the art for modifying the materials of the photoanode and the photocathode.

[0015] Furthermore, this differentiated spectral filtering makes it possible to consider limiting the infrared radiation received by the photoanode, which makes it possible to significantly reduce the heat transfer in the photoelectrochemical reactor, with an improvement in its lifetime (less degradation of materials). In addition, this differentiated spectral filtering makes it possible to consider limiting the ultraviolet radiation received by the photocathode, which also makes it possible to improve the lifetime of the photoelectrochemical reactor (less degradation of materials).

[0016] The installation according to the invention may include one or more of the following characteristics.

[0017] According to a characteristic of the invention, the first and second reflectors are designed to respectively reflect the first and second spectral domains according to respectively first and second different light intensities.

[0018] Thus, one advantage is that it is possible to modulate the power of the radiation received by the photoanode and the photocathode. This differentiation of light intensities makes it possible, in particular, to consider increasing the first light intensity in the ultraviolet to increase the efficiency of the photoanode, and reducing the second light intensity in the infrared to reduce heat transfer to the photocathode.

[0019] According to a characteristic of the invention:

[0020] - the photoanode comprises a photocatalytic layer made of a first semiconductor material having a band gap energy, noted Egi;

[0021] - the first reflector is designed to filter all or part of the wavelengths, noted Xi, of the incident solar radiation verifying À x where “h” is Planck’s constant and “c” is the speed of light in a vacuum.

[0022] Thus, one advantage provided is to increase the efficiency and durability of the photoelectrochemical reactor by deflecting the photoanode or removing all or part of the solar spectrum whose energy does not allow the photoanode to generate electron-hole pairs.

[0023] According to a characteristic of the invention, the first semiconductor material is chosen from titanium dioxide TiO2, bismuth vanadate BiVO i, zinc oxide ZnO, tin dioxide SnO2, tungsten trioxide WO3, ferric oxide Fe2O3.

[0024] Thus, an advantage provided by these "n" type materials is due to their stable physicochemical properties over time to efficiently generate electron-hole pairs, separate them (i.e. avoid their recombination) and transport them, as well as their quality of adsorption of reagents.

[0025] According to a characteristic of the invention, the second reflector is designed to filter wavelengths, denoted X2, of the incident solar radiation verifying λ2 < 400 nm.

[0026] Thus, an advantage provided is to be able to deflect towards the photoanode or suppress the ultraviolet radiation, too energetic for the strict needs of the photo-excitation of the photocathode, and which leads to a degradation of the photoelectrochemical reactor in the long term.

[0027] According to a characteristic of the invention:

[0028] - the photocathode comprises a photocatalytic layer made of a second semiconductor material having a band gap energy, denoted Eg2; - the second reflector is designed to filter all or part of the wavelengths, denoted X2, of the incident solar radiation verifying À2> - where “h” is Planck’s constant and “c” is the speed of light in a vacuum.

[0029] Thus, one advantage provided is to increase the efficiency of the photoelectrochemical reactor by eliminating all or part of the solar spectrum whose energy does not allow the photocathode to generate electron-hole pairs.

[0030] According to a characteristic of the invention, the second semiconductor material is chosen from copper oxide Cu2O, a perovskite, a delafossite, a spinel, silicon, boron arsenide BAs, tungsten selenide WSe2, zinc sulfide ZnS, indium phosphide InP, gallium-indium phosphide GaInP2.

[0031] Thus, an advantage provided by these “p” type materials is due to their stable physicochemical properties over time to efficiently generate electron-hole pairs, separate them (i.e. avoid their recombination) and transport them, as well as their quality of adsorption of reagents.

[0032] According to a characteristic of the invention, each of the first and second reflectors comprises at least one mirror chosen from a plane mirror, a parabolic mirror, a cylindro-parabolic mirror.

[0033] According to a characteristic of the invention, the first and second reflectors respectively comprise first and second coatings adapted to reflect the first and second spectral domains respectively.

[0034] Thus, one advantage provided is the ease of implementation to obtain the desired first and second spectral domains.

[0035] According to a characteristic of the invention, the installation comprises displacement means, configured to move the first and second reflectors according to the incident solar radiation so that the first and second reflectors respectively reflect the first and second spectral domains respectively towards the first and second walls.

[0036] Thus, an advantage provided is to optimize the intensity of the radiation reflected by the first and second reflectors towards the first and second walls respectively depending on the position of the sun. Definitions

[0037] — By “reactor” we mean an enclosure intended to receive a reaction volume.

[0038] — By "photoelectrochemical" we mean the use of light and chemical reactions to produce electricity.

[0039] — By "photoanode" we mean an electrode sensitive to light, and where an electrochemical oxidation reaction takes place.

[0040] — By “photocathode” we mean an electrode sensitive to light, and where an electrochemical reduction reaction takes place.

[0041] — By "first (or second) spectral domain" is meant a restriction of the solar spectrum in terms of wavelengths reflected by the corresponding reflector.

[0042] — By "photocatalytic layer" is meant a layer capable of generating at least one electron-hole pair when the layer is subjected to photoexcitation (with sufficient energy), and where an oxidation-reduction reaction can take place on the surface of the layer. The photocatalytic layer can be continuous, or discontinuous when the photocatalyst (i.e. the material of the photocatalytic layer) is in suspension, i.e. dispersed in fine particles inside the reaction volume.

[0043] — By “filter” we mean that the reflector is designed to:

[0044] (i) directly filter all or part of the corresponding wavelengths by its intrinsic characteristics, or

[0045] (ii) indirectly filter all or part of the corresponding wavelengths by deflecting the incident solar radiation towards other surfaces.

[0046] — By "perovskite" we mean calcium titanate CaTiO3, as well as all compounds of the empirical formula ABO3 possessing the same crystal structure.

[0047] — By "delafossite" we mean an oxide of iron and copper CuFeCL, as well as all compounds of the empirical formula ABO2 possessing the same crystal structure.

[0048] — By "spinel" we mean an oxide of magnesium and aluminum MgAl2O4 as well as minerals with the gross formula AB2X4, in particular CuM2O4, where M=A1, Cr, Mn, Fe, Co.

[0049] Brief description of the drawings

[0050] Other features and advantages will become apparent in the detailed description of various embodiments of the invention, the description being accompanied by examples and references to the attached drawings.

[0051] Figure 1 is a schematic longitudinal sectional view of a photoelectrochemical reactor which can equip an installation according to the invention, illustrating an application for the production of a fuel (eg methanol CH3OH) from a reduction of carbon dioxide CO2.

[0052] Figure 2 is a strip diagram of a photoelectrochemical cell, the photoanode and photocathode of which each have a photocatalytic layer made of a semiconductor material.

[0053] Figure 3 is a schematic side view of an installation according to the invention, illustrating a first arrangement of the first and second reflectors of the optical system.

[0054] Figure 4 is a schematic side view of an installation according to the invention, illustrating a second arrangement of the first and second reflectors of the optical system.

[0055] Figure 5 is a schematic side view of an installation according to the invention, illustrating an embodiment of the first and second reflectors of the optical system, where each of the first and second reflectors comprises a plurality of mirrors.

[0056] It should be noted that the drawings described above are schematic, and are not necessarily to scale for the sake of readability and to simplify their understanding.

[0057] Detailed description of the implementation methods

[0058] Identical elements or those providing the same function will bear the same references for the different embodiments, for the sake of simplification.

[0059] An object of the invention is an installation, comprising:

[0060] - a solar photoelectrochemical reactor 1, comprising: a photoanode PA and a photocathode PC, sensitive to solar radiation RS; first and second walls Pl, P2, transparent to solar radiation RS, facing respectively the photoanode PA and the photocathode PC;

[0061] - an optical system, arranged outside the solar photoelectrochemical reactor 1, and comprising first and second reflectors RI, R2, designed to respectively reflect: a first spectral domain of incident solar radiation RS towards the first wall PI, a second spectral domain of incident solar radiation RS, different from the first spectral domain, towards the second wall P2.

[0062] Solar photoelectrochemical reactor

[0063] By way of non-limiting examples, the solar photoelectrochemical reactor 1 may have a circular, square, rectangular, or triangular cross-section. The solar photoelectrochemical reactor 1 is preferably of the tubular type. The solar photoelectrochemical reactor 1 comprises first and second walls P1, P2 transparent to solar radiation RS, and facing respectively the photoanode PA and the photocathode PC. The first and second walls P1, P2 will be called “frontal”. The solar photoelectrochemical reactor 1 comprises an enclosure P1, P2, P intended to receive a reaction volume, and capable of delimiting an anode chamber and a cathode chamber. The enclosure P1, P2, P comprises the first and second front walls P1, P2, and longitudinal walls P connecting the first and second front walls P1, P2. The longitudinal walls P are preferably opaque to solar radiation RS.However, the longitudinal walls P may be partly transparent to solar radiation RS. The anode chamber is intended to receive a first electrolyte ELI while the cathode chamber is intended to receive a second electrolyte EL2. The anode chamber and the cathode chamber are separated by a membrane 3. The membrane 3 is advantageously an ion exchange membrane, adapted to diffuse certain ions produced by the photoelectrochemical reactor 1, for example the H ions. +. By way of non-limiting example, the membrane 3 may be made of nafion®. The first electrolyte ELI and the second electrolyte EL2 may be in the liquid phase or in the gas phase. By way of non-limiting example, the first electrolyte ELI may be a liquid phase of water H2O while the second electrolyte EL2 may be a gas phase of carbon dioxide CO2. The first electrolyte ELI may be identical to the second electrolyte EL2, for example water H2O in the case of the production of dihydrogen H2.

[0064] The solar photoelectrochemical reactor 1 comprises a photoanode PA sensitive to solar radiation RS. The photoanode PA advantageously comprises a photocatalytic layer 10 made of a first semiconductor SCI material having a bandgap energy, denoted Egi. The first semiconductor material SCI is advantageously of type n, and chosen from titanium dioxide TiO2, bismuth vanadate BiVCh, zinc oxide ZnO, tin dioxide SnO2, tungsten trioxide WO3, ferric oxide Fe2O3. More specifically, the photoanode PA may comprise an electrode E covered with the photocatalytic layer 10. By way of non-limiting example, the electrode E may be made of an electrically conductive material, such as a metallic material (eg Ag, Al). The photocatalytic layer 10 may be discontinuous.In other words, the photocatalytic layer 10 of the photoanode PA can be in suspension, that is to say dispersed in fine particles inside the reaction volume, in order to improve the mass transfer at the interface between the first electrolyte ELI and the first semiconductor material SCI.

[0065] As a variant of the photocatalytic layer 10, the photoanode PA may comprise an electrode E covered with a photovoltaic layer, i.e. a layer capable of generating at least one electron-hole pair when the layer is subjected to photoexcitation. As non-limiting examples, the photovoltaic layer may comprise:

[0066] - a perovskite photovoltaic cell (calcium titanate CaTiO3);

[0067] - a cadmium telluride CdTe photovoltaic cell;

[0068] - a CIGS type photovoltaic cell (copper, indium, gallium, selenium);

[0069] - a CZTS type photovoltaic cell (copper, zinc, tin, sulfur);

[0070] - a photovoltaic cell based on crystalline silicon, in particular with amorphous silicon / crystalline silicon heterojunction;

[0071] - a monolithic multi-junction type architecture, such as cells based on III-V materials, silicon / perovskite tandem cells.

[0072] The solar photoelectrochemical reactor 1 comprises a photocathode PC sensitive to solar radiation RS. The photocathode PC advantageously comprises a photocatalytic layer 20 made of a second semiconductor material SC2 having a band gap energy, denoted Eg2. The second semiconductor material SC2 is advantageously of p-type, and chosen from copper oxide Cu2O, a perovskite, a delafossite (for example copper-based, such as CuFeO2, CUA1O2, CuCrO2, CuRhO2), a spinel (eg CuMAL where M=A1, Cr, Mn, Fe, Co), silicon, boron arsenide BAs, tungsten selenide WSe2, zinc sulfide ZnS, indium phosphide InP, gallium-indium phosphide GaInP2. More specifically, the photocathode PC may comprise an electrode E covered with the photocatalytic layer 20. By way of non-limiting example, the electrode E may be made of an electrically conductive material, such as a metallic material (eg Ag, Al).The photocatalytic layer 20 may be discontinuous. In other words, the photocatalytic layer 20 of the photocathode PC may be in suspension, that is to say dispersed in fine particles inside the reaction volume, in order to improve the mass transfer at the interface between the second electrolyte EL2 and the second semiconductor material SC2.

[0073] As a variant of the photocatalytic layer 20, the photocathode PC may comprise an electrode E covered with a photovoltaic layer, i.e. a layer capable of generating at least one electron-hole pair when the layer is subjected to photoexcitation. As non-limiting examples, the photovoltaic layer may comprise:

[0074] - a perovskite photovoltaic cell (calcium titanate CaTiC) / ;

[0075] - a cadmium telluride CdTe photovoltaic cell;

[0076] - a CIGS type photovoltaic cell (copper, indium, gallium, selenium);

[0077] - a CZTS (copper, zinc, tin, sulfur) type photovoltaic cell; - a crystalline silicon-based photovoltaic cell, in particular with amorphous silicon / crystalline silicon hetero junction;

[0078] - a monolithic multi-junction type architecture, such as cells based on III-V materials, silicon / perovskite tandem cells.

[0079] The photoanode PA and the photocathode PC are advantageously connected by an external circuit in which electrons c generated by the photoanode PA circulate. The photons of the solar radiation RS1 reflected by the first reflector RI are absorbed by the first semiconductor material SCI, and excite the electrons of its valence band BV1, which can then generate electron-hole pairs eVh +. More precisely, an electron e can cross the band gap Egi of the first semiconductor material SCI if the photons of the solar radiation RS1 reflected by the first reflector RI are sufficiently energetic, then the electron e can then pass from the valence band BV1 to the conduction band BC1 of the first semiconductor material SCI. A hole h + (i.e. an absence of electron or vacancy) is simultaneously created in the valence band BV1. The holes h +reach the surface of the photocatalytic layer 10 of the photoanode PA where they can react with the first electrolyte ELI. The electrons e pass from the conduction band BC1 of the first semiconductor material SCI to the valence band BV2 of the second semiconductor material SC2 via the external circuit, thus creating a photocurrent. At the same time, the photons of the solar radiation RS2 reflected by the second reflector R2 are absorbed by the second semiconductor material SC2, and excite the electrons of its valence band BV2, which can then generate electron-hole pairs eVh +. More precisely, an electron e can cross the band gap Eg2 of the second semiconductor material SC2 if the photons of the solar radiation RS2 reflected by the second reflector R2 are sufficiently energetic, then the electron e can then pass from the valence band BV2 to the conduction band BC2 of the second semiconductor material SC2. The electrons e from the conduction band BC2 of the second semiconductor material SC2 reach the surface of the photocatalytic layer 20 of the photocathode PC where they can react with the second electrolyte EL2.

[0080] Optical system

[0081] The optical system is arranged outside the solar photoelectrochemical reactor 1. In other words, the optical system is located outside the solar photoelectrochemical reactor 1.

[0082] The optical system comprises a first reflector RI designed to reflect a first spectral domain of incident solar radiation RS towards the first wall PL. The first spectral domain is restrictive compared to the entire solar spectrum. The first reflector RI is advantageously arranged to reflect the first spectral domain of the incident solar radiation RS so that the solar radiation RS1 reflected by the first reflector RI extends in a direction parallel to the normal to the surface of the first wall PI of the photoelectrochemical reactor 1. Such an arrangement of the first reflector RI makes it possible to maximize the intensity of the radiation RS1 received by the photoanode PA, with a view to increasing the efficiency of the photoelectrochemical reactor 1.

[0083] The optical system comprises a second reflector R2 designed to reflect a second spectral domain of incident solar radiation RS towards the second wall P2. The second spectral domain is different from the first spectral domain. The second spectral domain is restrictive with respect to the entire solar spectrum. The second reflector R2 is advantageously arranged to reflect the second spectral domain of the incident solar radiation RS so that the solar radiation RS2 reflected by the second reflector R2 extends in a direction parallel to the normal to the surface of the second wall P2 of the photoelectrochemical reactor 1. Such an arrangement of the second reflector R2 makes it possible to maximize the intensity of the radiation RS2 received by the photocathode PC, with a view to increasing the efficiency of the photoelectrochemical reactor 1.

[0084] The first and second reflectors RI, R2 are advantageously designed to respectively reflect the first and second spectral domains according to respectively first and second different light intensities. By way of non-limiting examples, the first and second reflectors RI, R2 may comprise:

[0085] - Fresnel mirrors having lens matrices (called linear Fresnel lenses) which can be focused or defocused so as to modulate the reflected light intensity for a given incidence of solar radiation RS;

[0086] - heliostats that can be focused or defocused so as to modulate the reflected light intensity for a given incidence of solar radiation RS.

[0087] When the photoanode PA comprises a photocatalytic layer 10 made of a first semiconductor material SCI having a band gap energy, noted Egi, then the first reflector RI is advantageously designed to filter all or part of the wavelengths, noted Xi, of the incident solar radiation RS verifying À x > - where "h" is Planck's constant and "c" is the speed of light in vacuum. The first RI reflector then acts as a high-pass filter for the energy of the photons reflected by the first RI reflector (low-pass filter for wavelengths).

[0088] The second reflector R2 is advantageously designed to filter wavelengths, denoted 2, of the incident solar radiation RS verifying λ2 < 400 nm. The second reflector R2 then acts as a low-pass filter for the energy of the photons reflected by the second reflector R2 (high-pass filter with respect to the wavelengths).

[0089] When the photocathode PC comprises a photocatalytic layer 20 made of a second semiconductor material SC2 having a band gap energy, denoted Eg2, then the second reflector R2 is advantageously designed to filter all or part of the wavelengths, noted X2, of the incident solar radiation RS verifying À2> - where “h” is Planck's constant and "c" is the speed of light in vacuum. The second reflector R2 then acts as a high-pass filter for the energy of the photons reflected by the second reflector R2 (low-pass filter for wavelengths).

[0090] Advantageously, the second reflector R2 is designed to reflect (band-pass filter) the wavelengths of the incident solar radiation RS verifying: hc

[0091] 400 nm < À2< — — Eg2

[0092] In practice, the band gap energy Eg2 of the second semiconductor material SC2 is lower than the band gap energy Egi of the first semiconductor material SCI, so that — > 400 nm.

[0093] 4 Eg2

[0094] Each of the first and second reflectors RI, R2 advantageously comprises at least one mirror M1, M2 chosen from a plane mirror, a parabolic mirror, a cylindro-parabolic mirror.

[0095] Advantageously, the first and second reflectors RI, R2 respectively comprise first and second coatings adapted to reflect the first and second spectral domains respectively. By way of non-limiting example, it is possible to use:

[0096] — ultraviolet mirrors (called “cold”) which filter visible energy and infrared energy by transmission to the reflector (e.g. quartz glass — fused silica) or by absorption by the reflector (e.g. aluminum);

[0097] — visible / infrared mirrors (called “cold”) which filter ultraviolet energy by transmission to the reflector or by absorption by the reflector.

[0098] Such cold mirrors are marketed, for example, by the companies THORLABS, NTFL of Newportlab, KANEKA, etc.

[0099] By way of non-limiting example, the first spectral domain is located in the ultraviolet while the second spectral domain is located in the infrared or in the visible.

[0100] The installation advantageously comprises displacement means, configured to move the first and second reflectors RI, R2 according to the incident solar radiation RS so that the first and second reflectors RI, R2 respectively reflect the first and second spectral domains respectively towards the first and second walls Pl, P2. The displacement means advantageously comprise a solar tracker T, configured to orient itself according to the position of the sun in the sky.

[0101] The invention is not limited to the embodiments disclosed. Those skilled in the art are able to consider their technically effective combinations and to substitute equivalents for them.

Claims

CLAIMS 1. Installation, including: - a solar photoelectrochemical reactor (1), comprising: a photoanode (PA) and a photocathode (PC), sensitive to solar radiation (RS); first and second walls (Pl, P2), transparent to solar radiation (RS), facing respectively the photoanode (PA) and the photocathode (PC); - an optical system, arranged outside the solar photoelectrochemical reactor (1), and comprising first and second reflectors (RI, R2), designed to respectively reflect: a first spectral domain of incident solar radiation (RS) towards the first wall (PI), a second spectral domain of incident solar radiation (RS), different from the first spectral domain, towards the second wall (P2).

2. Installation according to claim 1, in which the first and second reflectors (RI, R2) are designed to respectively reflect the first and second spectral domains according to respectively first and second different light intensities.

3. Installation according to claim 1 or 2, in which: - the photoanode (PA) comprises a photocatalytic layer (10) made of a first semiconductor material (SCI) having a band gap energy, noted Egi; - the first reflector (RI) is designed to filter all or part of the wavelengths, noted Xi, of the incident solar radiation (RS) verifying À x > - , where “h” is the constant of E 3i Planck and “c” is the speed of light in vacuum.

4. Installation according to claim 3, in which the first semiconductor material (SCI) is chosen from titanium dioxide TiO2, bismuth vanadate BiVO4, zinc oxide ZnO, tin dioxide SnO2, tungsten trioxide WO3, ferric oxide Fe2C>3.

5. Installation according to one of claims 1 to 4, in which the second reflector (R2) is designed to filter wavelengths, noted X2, of the incident solar radiation (RS) verifying λ2 < 400 nm.

6. Installation according to one of claims 1 to 5, in which: - the photocathode (PC) comprises a photocatalytic layer (20) made of a second semiconductor material (SC2) having a band gap energy, denoted Eg2; - the second reflector (R2) is designed to filter all or part of the wavelengths, noted X2, of the incident solar radiation (RS) verifying À2> - , where “h” is the constant of E 32 Planck and “c” is the speed of light in vacuum.

7. Installation according to claim 6, in which the second semiconductor material (SC2) is chosen from copper oxide Cu2O, a perovskite, a delafossite, a spinel, silicon, boron arsenide BAs, tungsten selenide WSe2, zinc sulfide ZnS, indium phosphide InP, gallium-indium phosphide GaInP2.

8. Installation according to one of claims 1 to 7, in which each of the first and second reflectors (RI, R2) comprises at least one mirror (Ml, M2) chosen from a plane mirror, a parabolic mirror, a cylindro-parabolic mirror.

9. Installation according to one of claims 1 to 8, in which the first and second reflectors (RI, R2) respectively comprise first and second coatings adapted to reflect the first and second spectral domains respectively.

10. Installation according to one of claims 1 to 9, in which: - the first spectral domain is located in the ultraviolet; - the second spectral domain is located in the infrared or in the visible.

11. Installation according to one of claims 1 to 10, comprising displacement means, configured to move the first and second reflectors (RI, R2) according to the incident solar radiation (RS) so that the first and second reflectors (RI, R2) respectively reflect the first and second spectral domains respectively towards the first and second walls (Pl, P2).

Images