Solar photocatalytic water splitting hydrogen production technical system integrated with band gap complementary light harvesting material

Abstract

The invention discloses a solar photocatalytic water splitting hydrogen production technical system integrated with a band gap complementary light harvesting material, and belongs to the technical field of solar photocatalytic production of solar fuel. The whole system is of a laminated type and sequentially comprises a wide-band-gap semiconductor light absorption unit (photocatalysis system II), a charge and proton transmission carrier and a narrow-band-gap semiconductor light absorption unit (photocatalysis system I) from top to bottom. The photocatalytic system II mainly absorbs ultraviolet light and visible light in a solar spectrum and oxidizes water to generate oxygen, protons and electrons, and the protons are transmitted to the photocatalytic system I through a transmission carrier; the photocatalytic system I absorbs long-wave visible light and near-infrared light, protons are reduced to generate hydrogen, and the hydrogen is collected in a centralized manner; the photocatalytic system I and the photocatalytic system II are connected through charges and a proton transmission carrier, so that circulation of the whole system is realized. According to the technical system, hydrogen production and oxygen production reaction spaces are separated, and the problem that hydrogen and oxygen are difficult to separate in a photocatalytic water splitting system can be fundamentally solved.

Description

Technical Field

[0001] The present application relates to a solar photocatalytic water decomposition hydrogen production technology system with integrated bandgap complementary light-harvesting materials, belonging to the technical field of solar photocatalytic production of solar fuels. Background Art

[0002] Clean energy, environmental protection and green sustainable development have become the consensus of the international community, and the development of clean and renewable energy is imminent. As the "mother of energy" on earth, solar energy has the advantages of being clean, abundant and renewable. Its efficient conversion and utilization is an ideal way to solve energy and environmental problems. Among them, decomposing water to produce hydrogen through solar energy is one of the most effective ways to utilize solar energy. As an energy carrier, hydrogen has the advantages of high combustion calorific value and cleanliness. It can not only be used directly as a fuel to replace scarce fossil energy, but also as an industrial raw material to synthesize industrial chemicals such as methanol and ammonia. Therefore, achieving efficient decomposition of water to produce hydrogen through artificial photosynthesis is a fundamental way to solve energy and environmental problems.

[0003] At present, the main ways to convert solar energy into hydrogen energy through artificial photosynthesis are: photovoltaic-electrolysis coupling system, photoelectrocatalytic system and powder photocatalyst system. Among them, solar photocatalytic water decomposition to produce hydrogen has the advantages of simple process equipment and low one-time investment cost, and is one of the most promising technologies for large-scale solar hydrogen production in the future. However, the biggest problem currently facing solar photocatalytic hydrogen production is the low solar energy conversion efficiency, and there are safety hazards in the mixing of hydrogen and oxygen, and the separation of hydrogen and oxygen is difficult and costly, which greatly limits future large-scale applications. Therefore, how to improve the efficiency of solar photocatalytic hydrogen production and solve the problem of hydrogen and oxygen separation are the current research focuses of photocatalytic water decomposition. The K. Domen research group used Al-doped SrTiO3 as a photocatalyst for full water decomposition and conducted preliminary large-scale experimental exploration outdoors. The solar energy to hydrogen energy conversion efficiency was 0.4-0.76%. The system was equipped with a hydrogen and oxygen collection and separation system based on a separation membrane, but the gas separation cost was high and the separation was not thorough (Nature, 2021, 98, 304-307). The maximum solar energy to hydrogen conversion efficiency of this work is still less than 1.0%, and more than 20% of the hydrogen in the entire system remains in the original mixed gas, which still poses a great safety hazard. The cost invested in hydrogen separation also accounts for a large proportion of the entire system. Summary of the invention

[0004] In order to solve the problems of low solar energy conversion efficiency, safety hazards of coexistence of hydrogen and oxygen, difficulty in separating hydrogen and oxygen, and difficulty in large-scale application in the existing technology of solar photocatalytic water decomposition to produce hydrogen, the applicant has studied and developed a "hydrogen farm" strategy for scalable solar water decomposition to produce hydrogen, and realized large-scale solar water decomposition to produce hydrogen through the coupling system of photocatalysis and photoelectrocatalysis (Angew.Chem.Int.Ed.,2020,59,9653-9658). This technology not only increases the conversion efficiency of solar energy to hydrogen energy to 1.85%, but more importantly, it fundamentally solves the problem of separation of hydrogen and oxygen, and has good prospects for industrialization. However, in addition to the fact that the solar energy conversion efficiency of this technology still needs to be improved, the entire system is not a full photocatalytic system in the full sense, and it also requires the assistance of electrochemical processes, and the two separate systems of photocatalysis and photoelectrocatalysis are also relatively complex. Based on this, in order to solve the aforementioned problems and defects, the applicant discloses in this application a technical solution for stacked solar photocatalytic water decomposition to produce hydrogen. The utilization rate of solar energy is improved by complementing the light absorption of wide-bandgap semiconductors and narrow-bandgap semiconductors and imitating the characteristics of the Z-scheme principle of the natural photosynthetic system. The efficiency of solar energy to hydrogen conversion is expected to exceed 10%, and hydrogen and oxygen are produced in two systems separately in space, which fundamentally solves the safety hazards of the coexistence of hydrogen and oxygen and the difficulty of separating hydrogen and oxygen. As a cheap, efficient and scalable method for solar photocatalytic water decomposition to produce hydrogen, this technology is expected to realize large-scale industrial solar photocatalytic hydrogen production.

[0005] This application adopts the following technical solutions:

[0006] According to the first aspect of the present application, a solar photocatalytic water decomposition hydrogen production technology system integrating bandgap complementary light-harvesting materials is provided, including a stacked photocatalytic hydrogen production system;

[0007] The stacked photocatalytic hydrogen production system comprises a stacked and relatively isolated photocatalytic system II and a photocatalytic system I;

[0008] The photocatalytic system II and the photocatalytic system I are connected via a charge and proton transfer system;

[0009] The charge and proton transport system includes relatively independent charge transport carriers and proton transport carriers;

[0010] The photocatalytic system II includes a wide bandgap semiconductor light absorbing material;

[0011] The photocatalytic system I comprises a narrow bandgap semiconductor light-absorbing material;

[0012] The process of solar photocatalytic decomposition of water to produce hydrogen includes: in the photocatalytic system II, a wide bandgap semiconductor light absorption unit absorbs ultraviolet light and short-wave visible light in the solar spectrum, oxidizes water to produce oxygen, protons and electrons, releases oxygen into the atmosphere, and transfers protons and electrons to the photocatalytic system I through a proton transport carrier and a charge transport carrier, respectively; in the photocatalytic system I, a narrow bandgap semiconductor light absorption unit absorbs long-wave visible light and near-infrared light, reduces protons to produce hydrogen, and the hydrogen is collected in a centralized manner.

[0013] Optionally, the absorption band of the wide bandgap semiconductor light absorbing material is between 300 and 700 nm;

[0014] Optionally, the absorption band edge of the narrow-bandgap semiconductor light-absorbing material is between 500 and 1000 nm.

[0015] Optionally, the proton transport carrier is selected from at least one of a pump system of an external storage tank, an isolation system of a high-transmittance material with pores and the pores are filled with ion exchange membranes, a high-transmittance ion conduction membrane isolation system, and a high-transmittance membrane isolation system with charge and proton conduction functions.

[0016] Optionally, the charge transfer carrier is selected from at least one of a liquid soluble ion pair with a redox potential between 0 and 1.23 V, a solid energy storage medium with a redox potential between 0 and 1.23 V, a solid medium with a charge transfer function, and a solid medium with a charge and proton transfer function.

[0017] Optionally, the electron carrier in the charge transport carrier is selected from Fe 3+ / Fe 2+ 、Fe(CN)6 3- / Fe(CN)6 4- IO3 - / I - 、I3 - / I - Sn 4+ / Sn 2+ 、SO4 2- / SO3 2- , VO 2+ / VO2 + , Cu 2+ / Cu + 、Co(NH3)6 3+ / Co(NH3)6 2+ 、[Co(phen)3] 3+ / [Co(phen)3] 2+ 、[Co(bpy)3] 3+ / [Co(bpy)3] 2+ 、[P2W 18 O62 ] 6- / [P2W 18 O 62 ] (6+n)- At least one soluble ion pair in.

[0018] Optionally, the valence band top position of the wide bandgap semiconductor light absorbing material is more positive than the oxidation potential of water, and the conduction band bottom position is more negative than the redox potential of the electron carrier in the charge transport carrier;

[0019] Optionally, the valence band top position of the narrow bandgap semiconductor light absorbing material is more positive than the redox potential of the electron carrier in the charge transport carrier, and the conduction band bottom position is more negative than the reduction potential of the proton.

[0020] Optionally, the charge transfer carrier is selected from at least one solid medium of carbon-based materials, metal materials, and conductive polymer materials.

[0021] Optionally, the carbon-based material is selected from at least one of graphene and carbon nanotubes.

[0022] Optionally, the metal material is selected from at least one of Au and Ag.

[0023] Optionally, the proton transport carrier is selected from at least one of a perfluorosulfonic acid membrane, a polytetrafluoroethylene membrane, and a polyvinylidene fluoride membrane.

[0024] Optionally, the wide bandgap semiconductor light-absorbing material is selected from at least one of titanium oxide, zinc oxide, tungsten oxide, iron oxide, vanadium oxide, nitride carbide, tantalum nitride, tantalum oxynitride, zinc gallium oxynitride, bismuth vanadate, bismuth chromate, silver phosphate, strontium titanate, cobalt titanate, potassium tantalate, and bismuth tantalate.

[0025] Optionally, the narrow bandgap semiconductor light-absorbing material is selected from at least one of cuprous oxide, cadmium sulfide, tantalum nitride, barium tantalum oxynitride, magnesium tantalum oxynitride, zinc sulfide, bismuth sulfide, cadmium selenide, copper indium sulfide, gallium arsenide, gallium phosphide, carbon nitride, and silicon.

[0026] The beneficial effects of this application include:

[0027] (1) The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials provided in this application utilizes the complementary light absorption characteristics of two semiconductor photocatalysts to improve the utilization rate of solar energy. The solar energy to hydrogen energy conversion efficiency can exceed 10%, and it is expected to realize large-scale industrial solar photocatalytic hydrogen production.

[0028] (2) In the present application, hydrogen and oxygen are generated in two systems respectively, which overcomes the problems of difficulty in separating hydrogen and oxygen, safety hazards of hydrogen and oxygen mixing, and reverse reaction of hydrogen and oxygen.

[0029] (3) Compared with solar photocatalytic water splitting on a single photocatalyst, the requirements for the energy band positions of semiconductors for photocatalytic oxygen and hydrogen production in this application are greatly reduced. It is no longer necessary to meet the requirements that the valence band position must be lower than the water oxidation potential and the conduction band position must be higher than the proton reduction potential. Only one of the two requirements needs to be met.

[0030] (4) The present application has a wide range of choices for charge transfer carriers, including liquid soluble ion pairs or solid energy storage media with a redox potential between 0 and 1.23 V, or solid media with charge transfer function, or solid media with both charge and proton transfer functions.

[0031] (5) The present application is a stacked system that integrates light-harvesting materials with different band gaps, fully utilizes the solar spectrum, greatly improves the efficiency of solar energy utilization, and saves device footprint and cost.

[0032] (6) The application system is simple, low-cost, open, and highly operable, making it easy to implement large-scale applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the principle of the stacked solar photocatalytic water decomposition hydrogen production system described in this application.

[0034] Figure 2 This is a schematic diagram of the structure of the stacked solar photocatalytic water decomposition hydrogen production system described in this application.

[0035] Figure 3 Schematic diagram of the energy band structure of the stacked solar photocatalytic water decomposition hydrogen production system described in this application.

[0036] Figure 4 Schematic diagram of the UV-visible absorption spectra of the bandgap complementary light-harvesting material photocatalytic system II and the photocatalytic system I described in the present application.

[0037] Figure 5 This is a schematic diagram of the reactor structure in which the charge and proton transfer unit described in this application is an external storage tank.

[0038] Figure 6 This is a schematic diagram of the reactor structure in which the charge and proton transfer unit described in this application is a hybrid system of a high light transmittance material and an ion exchange membrane.

[0039] Figure 7 This is a schematic diagram of the reactor structure in which the charge and proton transfer unit described in the present application is a highly light-transmitting ion-conducting membrane.

[0040] Figure 8 The charge and proton transfer unit described in the present application is a schematic diagram of the reactor structure of a high-transmittance membrane isolation system with charge and proton conduction functions.

[0041] Fig. 9 It is the linear relationship between the band gap of the upper / lower semiconductor and STH and the band gap matching relationship between the upper / lower semiconductor under different oxygen / hydrogen production quantum efficiencies in this application.

[0042] Fig.10 It is the relationship between the upper / lower semiconductor band gap and STH under different oxygen / hydrogen production quantum efficiencies in this application.

[0043] Fig.11 Schematic diagram of the UV-visible absorption spectra of two semiconductor photocatalysts, WO3 and CdS, in Example 1 of the present application.

[0044] Fig.12 For BiVO4 and ZnSe:CuGa2Se in Example 2 of this application 3.5 Schematic diagram of the UV-visible absorption spectra of two semiconductor photocatalysts.

[0045] Fig.13 Schematic diagram of the UV-visible absorption spectra of the two semiconductor photocatalysts B / N / g-C3N4 and Si in Example 3 of the present application. DETAILED DESCRIPTION

[0046] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0048] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0049] The technology and principle of the solar photocatalytic water splitting hydrogen production technology system provided by the application with integrated bandgap complementary light-harvesting materials:

[0050] The solar photocatalytic water splitting hydrogen production technology system provided by the present application includes a stacked photocatalytic hydrogen production system ( Figure 1 ), from top to bottom are wide bandgap semiconductor light absorption unit (photocatalytic system II), charge and proton transport carrier, narrow bandgap semiconductor light absorption unit (photocatalytic system I). Among them, photocatalytic system II mainly absorbs ultraviolet and visible light in the solar spectrum, oxidizes water to produce oxygen and protons, and the protons are transferred to photocatalytic system I through the transport unit; photocatalytic system I absorbs long-wave visible light and near-infrared light, reduces protons to produce hydrogen, and the hydrogen is collected in a centralized manner; photocatalytic system I and photocatalytic system II are connected by charge and proton transport carriers to realize the circulation of the entire system ( Figure 2 ). Among them, the charge and proton transport carriers can be pumped by an external storage tank system (such as Figure 5 As shown), a highly light-transmitting material with pores, and an isolation system in which the pores are filled with ion exchange membranes (such as Figure 6 As shown), high light transmittance ion conduction membrane isolation system (as shown Figure 7 As shown), a highly transparent membrane isolation system with charge and proton conduction functions (such as Figure 8 shown).

[0051] This technology can achieve wide spectrum absorption and utilization of sunlight through the complementary light absorption characteristics of two semiconductor photocatalysts ( Figure 3 and Figure 4 ), which can improve the conversion efficiency of solar energy to hydrogen energy, and divide the photocatalytic water splitting reaction into two half reactions, hydrogen production and oxygen production, which are carried out on two photocatalysts respectively, solving the problems of safety hazards caused by the coexistence of hydrogen and oxygen, and the spatial separation of hydrogen and oxygen. Its basic reaction principle is:

[0052] Photocatalytic system II:

[0053] 2H2O→O2+4H + +4e -

[0054] nOx.+4e - →nRed.

[0055] Photocatalytic system I:

[0056] nRed.→nOx.+4e -

[0057] 4H + +4e - →2H2

[0058] Overall reaction:

[0059] 2H2O→O2+2H2

[0060] The solar energy to hydrogen energy conversion efficiency (STH) in this system is calculated by integrating the photon flux density in the AM1.5 standard solar spectrum as the number of absorbed photons based on the band gap of the semiconductor, and then combining the quantum efficiency of the semiconductor's photocatalytic oxygen or hydrogen production in the above reaction principle. The specific calculation formula is as follows:

[0061]

[0062]

[0063] Among them, n photon,i represents the number of photons in interval i; P i represents the proportion of the solar spectrum in interval i; E solarrepresents the total amount of incident solar energy (AM 1.5G); Represents the energy released by water; QE(λ i ) represents the quantum efficiency at the central wavelength of interval i, and the quantum efficiency at this wavelength is taken as the average quantum efficiency in interval i; h represents Planck's constant; c represents the speed of light.

[0064] During the implementation of the entire system, the reaction rates of photocatalytic system II and photocatalytic system I must match to ensure that the water splitting reaction can proceed efficiently. The slow end of the reaction rate will become the rate-limiting step. Therefore, the final STH is based on the utilization rate of sunlight (P i *λ i *QE(λ i ))The smaller end is used as the standard for calculation ( Fig. 9 and Fig.10 ).

[0065] Example 1

[0066] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the upper layer (photocatalytic system II) is a wide bandgap photocatalytic semiconductor that responds to ultraviolet light and short-wave visible light. In this embodiment, tungsten trioxide (WO3) material is used as an example, and its absorption band edge is located at about 440nm ( Fig.11 ), the band gap value is ~2.8eV, the bottom of the conduction band is at ~0.7V, and the top of the valence band is at ~3.5V, which is more positive than the oxidation potential of water and can realize the oxidation reaction of water.

[0067] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the lower layer (photocatalytic system I) is a narrow bandgap photocatalytic semiconductor that responds to long-wave visible light and near-infrared light. In this embodiment, cadmium sulfide (CdS) material is taken as an example, and its absorption band edge is located at about 520nm ( Fig.11 ), the band gap value is ~2.4eV, the valence band top is at ~1.9V, and the conduction band bottom is at around -0.5V, which is more negative than the reduction potential of protons, and can realize the reduction reaction of water to produce hydrogen.

[0068] The stacked photocatalytic hydrogen production system described in the present application, wherein the charge transfer carrier includes a soluble energy storage electrode pair ion, which connects the water oxidation reaction occurring in the photocatalytic system II with the water reduction reaction occurring in the photocatalytic system I. Its redox potential is between 0 and 1.23 V, and is more positive than the bottom position of the conduction band of the selected wide band gap semiconductor, which can capture photogenerated electrons to undergo a reduction reaction from an oxidized state to a reduced state; it is more negative than the top position of the valence band of the selected narrow band gap semiconductor, which can capture photogenerated holes to undergo an oxidation reaction from a reduced state to an oxidized state. In this embodiment, the electron carrier is Fe 3+ / Fe 2+Its redox potential is 0.77V, which is more positive than the bottom of WO3 conduction band (~0.7V) and more negative than the top of CdS valence band (~1.9V). 3+ To Fe 2+ The reduction reaction can also capture photogenerated holes to generate Fe 2+ To Fe 3+ oxidation reaction.

[0069] In this embodiment, the upper WO3 wide bandgap semiconductor absorbs ultraviolet light less than 440nm and short-wave visible light in the solar spectrum to generate photogenerated holes and photogenerated electrons. The photogenerated holes oxidize water to produce oxygen and protons, and the photogenerated electrons oxidize Fe 3+ Reduction to Fe 2+ Oxygen is released into the atmosphere, and protons and Fe 2+ The photogenerated electrons generated by CdS absorb long-wave visible light and near-infrared light greater than 440nm (through the WO3 layer) and less than 520nm in the solar spectrum, and the photogenerated holes reduce the protons to produce hydrogen. 2+ Oxidation to Fe 3+ The hydrogen is collected and then the high-valent Fe 3+ It is transported back to the upper WO3 photocatalytic system to complete the cycle of the entire system.

[0070] In this embodiment, the water decomposition reaction is divided into two half reactions, hydrogen production and oxygen production, which are carried out on two photocatalysts, WO3 and CdS, respectively, to solve the problem that it is difficult to achieve a complete water decomposition reaction on a single photocatalyst particle. This stacked system fully absorbs and utilizes sunlight through the complementary light absorption characteristics of the two semiconductor photocatalysts WO3 and CdS, and the utilization rate of sunlight reaches about 26% (λ<520nm), greatly improving the conversion efficiency of solar energy to hydrogen energy (STH). When the quantum efficiencies of WO3 photocatalytic water oxidation and CdS photocatalytic proton reduction reach 100% / 100%, 80% / 80%, 80% / 40%, 40% / 80%, 40% / 40%, 40% / 20%, 20% / 40%, 20% / 20%, the theoretical STH reaches 3.8%, 3.1%, 2.3%, 1.5%, 1.5%, 1.1%, 0.8%, 0.8% ( Fig.10 ). In addition, in this embodiment, the hydrogen production and oxygen production reaction spaces are separated, oxygen is released into the atmosphere, and hydrogen is collected centrally, which fundamentally solves the problem of difficult separation of hydrogen and oxygen in traditional photocatalytic water splitting systems.

[0071] Example 2

[0072] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the upper layer (photocatalytic system II) is a wide bandgap photocatalytic semiconductor that responds to ultraviolet light and short-wave visible light. In this embodiment, bismuth vanadate (BiVO4) material is taken as an example, and its absorption band edge is located at about 530nm ( Fig.12 ), the band gap value is ~2.4eV, the bottom of the conduction band is at ~0.2V, and the top of the valence band is at ~2.6V, which is more positive than the oxidation potential of water and can realize the oxidation reaction of water.

[0073] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the lower layer (photocatalytic system I) is a narrow bandgap photocatalytic semiconductor that responds to long-wave visible light and near-infrared light, in this embodiment, zinc selenide-copper gallium selenide solid solution (ZnSe:CuGa2Se 3.5 ) material as an example, its absorption band edge is located at around 725nm ( Fig.12 ), the band gap value is ~1.8eV, the top of the valence band is at ~0.9V, and the bottom of the conduction band is at around -0.9V, which is more negative than the reduction potential of protons, and can realize the reduction reaction of water to produce hydrogen.

[0074] The stacked photocatalytic hydrogen production system described in the present application, wherein the charge transfer carrier includes a soluble energy storage electrode pair ion, which connects the water oxidation reaction occurring in the photocatalytic system II with the water reduction reaction occurring in the photocatalytic system I. Its redox potential is between 0 and 1.23 V, and is more positive than the bottom position of the conduction band of the selected wide band gap semiconductor, which can capture photogenerated electrons to undergo a reduction reaction from an oxidized state to a reduced state; it is more negative than the top position of the valence band of the selected narrow band gap semiconductor, which can capture photogenerated holes to undergo an oxidation reaction from a reduced state to an oxidized state. In this embodiment, the electron carrier is Fe 3+ / Fe 2+ Its redox potential is 0.77 V, which is more positive than the bottom of the conduction band of BiVO4 (~0.2 V) and more positive than that of ZnSe:CuGa2Se 3.5 The valence band top (~0.9V) is more negative, which can capture photogenerated electrons to generate Fe 3+ To Fe 2+ The reduction reaction can also capture photogenerated holes to generate Fe 2+ To Fe 3+ oxidation reaction.

[0075] In this embodiment, the BiVO4 wide bandgap semiconductor on the upper layer absorbs ultraviolet light and short-wave visible light less than 530nm in the solar spectrum to generate photogenerated holes and photogenerated electrons. The photogenerated holes oxidize water to produce oxygen and protons, and the photogenerated electrons oxidize Fe 3+ Reduction to Fe 2+ Oxygen is released into the atmosphere, and protons and Fe 2+ is transferred to the lower layer ZnSe:CuGa2Se 3.5In narrow bandgap semiconductor photocatalytic systems. ZnSe:CuGa2Se 3.5 By absorbing the long-wave visible light and near-infrared light greater than 530nm (through the BiVO4 layer) and less than 725nm in the solar spectrum, the photogenerated electrons generated will reduce protons to produce hydrogen, and the photogenerated holes will reduce Fe 2+ Oxidation to Fe 3+ The hydrogen is collected and then the high-valent Fe 3+ It is transported back to the upper BiVO4 photocatalytic system to complete the cycle of the entire system.

[0076] In this embodiment, the water decomposition reaction is divided into two half reactions, hydrogen production and oxygen production, respectively in BiVO4 and ZnSe:CuGa2Se 3.5 The two photocatalysts are carried out on each other, solving the problem that it is difficult to achieve a complete water decomposition reaction on a single photocatalyst particle. This stacked system is made of BiVO4 and ZnSe:CuGa2Se 3.5 The complementary light absorption characteristics of the two semiconductor photocatalysts enable full absorption and utilization of sunlight, with a utilization rate of about 50% (λ<750nm), greatly improving the conversion efficiency of solar energy to hydrogen energy (STH). 3.5 (530nm<λ<750nm) have similar utilization rates for the solar spectrum, about 25% respectively. When BiVO4 photocatalytic water oxidation and ZnSe:CuGa2Se 3.5 The quantum efficiencies of photocatalytic proton reduction were 100% / 100%, 80% / 80%, 80% / 40%, 40% / 80%, 40% / 40%, 40% / 20%, 20% / 40%, 20% / 20%, and the theoretical STHs were 9.3%, 7.4%, 6.1%, 3.7%, 3.7%, 3.0%, 1.9%, 1.9% ( Fig.10 ). In addition, in this embodiment, the hydrogen production and oxygen production reaction spaces are separated, oxygen is released into the atmosphere, and hydrogen is collected centrally, which fundamentally solves the problem of difficult separation of hydrogen and oxygen in traditional photocatalytic water splitting systems.

[0077] Example 3

[0078] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the upper layer (photocatalytic system II) is a wide bandgap photocatalytic semiconductor that responds to ultraviolet light and short-wave visible light. In this embodiment, a boron-doped nitrogen-deficient carbon trinitrogen tetrakis (B / N / g-C3N4) material is used as an example, and its absorption band edge is located at about 600nm ( Fig.13 ), the band gap value is ~2.0eV, the bottom of the conduction band is at ~0.4V, and the top of the valence band is at ~2.4V, which is more positive than the oxidation potential of water and can realize the oxidation reaction of water.

[0079] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the lower layer (photocatalytic system I) is a narrow bandgap photocatalytic semiconductor that responds to long-wave visible light and near-infrared light. In this embodiment, silicon (Si) material is taken as an example, and its absorption band edge is located at about 1000nm ( Fig.13 ), the band gap value is ~1.1eV, the top of the valence band is at ~0.7V, and the bottom of the conduction band is at around -0.4V, which is more negative than the reduction potential of protons, and can realize the reduction reaction of water to produce hydrogen.

[0080] The stacked photocatalytic hydrogen production system described in the present application, wherein the charge transfer carrier includes a soluble energy storage electrode pair ion, which connects the water oxidation reaction occurring in the photocatalytic system II with the water reduction reaction occurring in the photocatalytic system I. Its redox potential is between 0 and 1.23 V, and is more positive than the bottom position of the conduction band of the selected wide band gap semiconductor, which can capture photogenerated electrons to undergo a reduction reaction from an oxidized state to a reduced state; and is more negative than the top position of the valence band of the selected narrow band gap semiconductor, which can capture photogenerated holes to undergo an oxidation reaction from a reduced state to an oxidized state. In this embodiment, the electron carrier is selected from I3 - / I - Its redox potential is 0.55 V, which is more positive than the bottom of the conduction band of B / N / g-C3N4 (~0.4 V) and more negative than the top of the valence band of Si (~0.7 V). - To I 3- The reduction reaction can also capture photogenerated holes to generate I3 - To I - oxidation reaction.

[0081] In this embodiment, the upper B / N / g-C3N4 wide bandgap semiconductor absorbs ultraviolet light and short-wave visible light less than 600nm in the solar spectrum to generate photogenerated holes and photogenerated electrons. The photogenerated holes oxidize water to produce oxygen and protons, and the photogenerated electrons oxidize I - Restore to I3 - Oxygen is released into the atmosphere, protons and I3 - The photogenerated electrons generated by Si absorb long-wave visible light and near-infrared light greater than 600nm (through the B / N / g-C3N4 layer) and less than about 1000nm in the solar spectrum, and the photogenerated holes reduce protons to produce hydrogen. 3- Oxidation to I - The hydrogen is collected and then converted into high-valence hydrogen. - It is transported back to the upper B / N / g-C3N4 photocatalytic system to realize the cycle of the entire system.

[0082] In this embodiment, the water splitting reaction is divided into two half reactions, hydrogen production and oxygen production, which are carried out on two photocatalysts, B / N / g-C3N4 and Si, respectively, solving the problem that it is difficult to achieve a complete water splitting reaction on a single photocatalyst particle. This stacked system fully absorbs and utilizes sunlight through the complementary light absorption characteristics of the two semiconductor photocatalysts B / N / g-C3N4 and Si, and the utilization rate of sunlight reaches about 70% (λ<1000nm), which greatly improves the conversion efficiency of solar energy to hydrogen energy (STH). Among them, the utilization rates of the solar spectrum of B / N / g-C3N4 (λ<600nm) and Si (600nm<λ<1000nm) are comparable, about 35% respectively. When the quantum efficiencies of the photocatalytic water oxidation of B / N / g-C3N4 and the photocatalytic proton reduction of Si reach 100% / 100%, 80% / 80%, 80% / 40%, 40% / 80%, 40% / 40%, 40% / 20%, 20% / 40%, and 20% / 20% respectively, the theoretical STH reaches 18%, 14.4%, 14.1%, 7.2%, 7.2%, 7.1%, 3.6%, and 3.6% respectively. Fig.10 ). In addition, in this embodiment, the hydrogen production and oxygen production reaction spaces are separated, oxygen is released into the atmosphere, and hydrogen is collected centrally, which fundamentally solves the problem of difficult separation of hydrogen and oxygen in traditional photocatalytic water splitting systems.

[0083] Example 4

[0084] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the upper layer (photocatalytic system II) is a wide bandgap photocatalytic semiconductor that responds to ultraviolet light and short-wave visible light. In this embodiment, bismuth vanadate (BiVO4) material is taken as an example, and its absorption band edge is located at about 530nm ( Fig.12 ), the band gap value is ~2.4eV, the bottom of the conduction band is at ~0.2V, and the top of the valence band is at ~2.6V, which is more positive than the oxidation potential of water and can realize the oxidation reaction of water.

[0085] The stacked photocatalytic hydrogen production system described in the present application, wherein the photocatalytic material of the lower layer (photocatalytic system I) is a narrow bandgap photocatalytic semiconductor that responds to long-wave visible light and near-infrared light, in this embodiment, zinc selenide-copper gallium selenide solid solution (ZnSe:CuGa2Se 3.5 ) material as an example, its absorption band edge is located at around 725nm ( Fig.12 ), the band gap value is ~1.8eV, the top of the valence band is at ~0.9V, and the bottom of the conduction band is at around -0.9V, which is more negative than the reduction potential of protons, and can realize the reduction reaction of water to produce hydrogen.

[0086] The stacked photocatalytic hydrogen production system described in the present application, wherein the charge transfer carrier includes a solid medium with a charge transfer function, which transfers the photogenerated electrons generated in the photocatalytic system II to the photocatalytic system I. In this embodiment, the charge carrier is selected from carbon nanotubes.

[0087] The stacked photocatalytic hydrogen production system described in the present application, wherein the proton transport carrier includes a highly light-transmitting ion conduction module, which transports the protons generated in the photocatalytic system II to the photocatalytic system I. In this embodiment, the charge carrier is a Nafion proton conduction module.

[0088] In this embodiment, the BiVO4 wide bandgap semiconductor on the upper layer absorbs ultraviolet light and short-wave visible light less than 530nm in the solar spectrum to generate photogenerated holes and photogenerated electrons, which oxidize water to produce oxygen and protons. The photogenerated electrons and protons are respectively transmitted to the ZnSe:CuGa2Se 3.5 In narrow bandgap semiconductor photocatalytic systems. ZnSe:CuGa2Se 3.5 By absorbing long-wave visible light and near-infrared light greater than 530nm (through the BiVO4 layer) and less than 725nm in the solar spectrum, the photogenerated electrons generated reduce protons to produce hydrogen and are collected centrally. The photogenerated holes recombine with the electrons transmitted by the carbon nanotubes to realize the circulation of the entire system.

[0089] In this embodiment, the water decomposition reaction is divided into two half reactions, hydrogen production and oxygen production, respectively in BiVO4 and ZnSe:CuGa2Se 3.5 The two photocatalysts are carried out on each other, solving the problem that it is difficult to achieve a complete water decomposition reaction on a single photocatalyst particle. This stacked system is made of BiVO4 and ZnSe:CuGa2Se 3.5 The complementary light absorption characteristics of the two semiconductor photocatalysts enable full absorption and utilization of sunlight, with a utilization rate of about 50% (λ<750nm), greatly improving the conversion efficiency of solar energy to hydrogen energy (STH). 3.5 (530nm<λ<750nm) have similar utilization rates for the solar spectrum, about 25% respectively. When BiVO4 photocatalytic water oxidation and ZnSe:CuGa2Se 3.5 The quantum efficiencies of photocatalytic proton reduction were 100% / 100%, 80% / 80%, 80% / 40%, 40% / 80%, 40% / 40%, 40% / 20%, 20% / 40%, 20% / 20%, and the theoretical STHs were 9.3%, 7.4%, 6.1%, 3.7%, 3.7%, 3.0%, 1.9%, 1.9% ( Fig.10). In addition, in this embodiment, the hydrogen production and oxygen production reaction spaces are separated, oxygen is released into the atmosphere, and hydrogen is collected centrally, which fundamentally solves the problem of difficult separation of hydrogen and oxygen in traditional photocatalytic water splitting systems.

[0090] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A solar photocatalytic water splitting hydrogen production technology system integrating bandgap complementary light-harvesting materials, characterized in that: It includes a stacked photocatalytic hydrogen production system; The stacked photocatalytic hydrogen production system comprises a stacked and relatively isolated photocatalytic system II and a photocatalytic system I; The photocatalytic system II and the photocatalytic system I are connected via a charge and proton transfer system; The charge and proton transport system includes relatively independent charge transport carriers and proton transport carriers; The photocatalytic system II includes a wide bandgap semiconductor light-absorbing material; The photocatalytic system I comprises a narrow bandgap semiconductor light absorbing material; The process of solar photocatalytic decomposition of water to produce hydrogen includes: in the photocatalytic system II, a wide bandgap semiconductor light absorption unit absorbs ultraviolet light and short-wave visible light in the solar spectrum, oxidizes water to produce oxygen, protons and electrons, releases oxygen into the atmosphere, and transfers protons and electrons to the photocatalytic system I through a proton transport carrier and a charge transport carrier, respectively; in the photocatalytic system I, a narrow bandgap semiconductor light absorption unit absorbs long-wave visible light and near-infrared light, reduces protons to produce hydrogen, and the hydrogen is collected in a centralized manner.

2. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The absorption band of the wide bandgap semiconductor light absorbing material is between 300 and 700 nm; Preferably, the absorption band edge of the narrow-bandgap semiconductor light-absorbing material is between 500 and 1000 nm.

3. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The proton transport carrier is selected from at least one of a pump system of an external storage tank, an isolation system of a high-transmittance material with pores and the pores are filled with an ion exchange membrane, a high-transmittance ion conduction membrane isolation system, and a high-transmittance membrane isolation system with charge and proton conduction functions.

4. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The charge transfer carrier is selected from at least one of a liquid soluble ion pair with a redox potential between 0 and 1.23 V, a solid energy storage medium with a redox potential between 0 and 1.23 V, a solid medium with a charge transfer function, and a solid medium with a charge and proton transfer function.

5. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 4 is characterized in that: The electron carrier in the charge transport carrier is selected from Fe 3+ / Fe 2+ 、Fe(CN)6 3- / Fe(CN)6 4- IO3 - / I - 、I3 - / I - Sn 4+ / Sn 2+ 、SO4 2- / SO3 2- , VO 2+ / VO2 + , Cu 2+ / Cu + 、Co(NH3)6 3+ / Co(NH3)6 2+ 、[Co(phen)3] 3+ / [Co(phen)3] 2+ 、[Co(bpy)3] 3+ / [Co(bpy)3] 2+ 、[P2W 18 O 62 ] 6- / [P2W 18 O 62 ] (6+n)- At least one soluble ion pair in the.

6. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 5 is characterized in that: The valence band top position of wide band gap semiconductor light absorbing materials is more positive than the oxidation potential of water, and the conduction band bottom position is more negative than the redox potential of the electron carrier in the charge transport carrier; Preferably, the valence band top position of the narrow bandgap semiconductor light absorbing material is more positive than the redox potential of the electron carrier in the charge transport carrier, and the conduction band bottom position is more negative than the reduction potential of the proton.

7. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The charge transfer carrier is selected from at least one solid medium selected from carbon-based materials, metal materials, and conductive polymer materials; Preferably, the carbon-based material is selected from at least one of graphene and carbon nanotubes; Preferably, the metal material is selected from at least one of Au and Ag.

8. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The proton transport carrier is selected from at least one of a perfluorosulfonic acid membrane, a polytetrafluoroethylene membrane, and a polyvinylidene fluoride membrane.

9. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The wide bandgap semiconductor light-absorbing material is selected from at least one of titanium oxide, zinc oxide, tungsten oxide, iron oxide, vanadium oxide, nitride carbide, tantalum nitride, tantalum oxynitride, zinc gallium oxynitride, bismuth vanadate, bismuth chromate, silver phosphate, strontium titanate, cobalt titanate, potassium tantalate, and bismuth tantalate.

10. The solar photocatalytic water splitting hydrogen production technology system with integrated bandgap complementary light-harvesting materials according to claim 1 is characterized in that: The narrow bandgap semiconductor light-absorbing material is selected from at least one of cuprous oxide, cadmium sulfide, tantalum nitride, barium tantalum oxynitride, magnesium tantalum oxynitride, zinc sulfide, bismuth sulfide, cadmium selenide, copper indium sulfide, gallium arsenide, gallium phosphide, carbon nitride, and silicon.

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