Perovskite photoanode and photoelectrochemical water splitting system using same

Abstract

The present invention relates to a perovskite photoanode and, more specifically, to a perovskite photoanode comprising: an oxygen generation part comprising a first lower electrode, a first electron transport layer formed on the first lower electrode, a perovskite first light absorbing layer formed on the first electron transport layer, a first hole transport layer formed on the first light absorbing layer, a first upper electrode formed on the first hole transport layer, a first Ni thin-film layer formed on the first upper electrode, and an oxygen evolution reaction catalyst layer formed on the first Ni thin film layer; and a passivation part comprising a second lower electrode, a second electron transport layer formed on the second lower electrode layer, a perovskite second light absorbing layer formed on the second electron transport layer, a second hole transport layer formed on the second light absorbing layer, a second upper electrode formed on the second hole transport layer, and a second Ni thin-film layer formed on the second upper electrode, wherein the first lower electrode and the second upper electrode are electrically connected to each other.

Description

Perovskite photoanode and photoelectrochemical water splitting system using the same

[0001] The present invention relates to a perovskite (PSK) photoanode and a photoelectrochemical water splitting system using the same.

[0002]

[0003] Since Fujishima and Honda first demonstrated solar hydrogen (H2) production using a TiO2 photoanode in 1972, photoelectrochemical (PEC) water splitting has attracted considerable attention as a promising technology for solar hydrogen production. The performance of a PEC cell is largely determined by the photoanode, which must be made of earth-abundant elements, be stable in water, and have a high solar-to-hydrogen (STH) efficiency of greater than 10% to make a PEC cell a practically viable solar H2 production system. The primary strategy to date for obtaining such photoanodes has been to utilize intrinsically stable oxide semiconductors, such as TiO2, Fe2O3, WO3, and BiVO4, and to improve their efficiency by applying various modification strategies, including doping, morphology control, heterojunctions, or heteroduplex configurations. Despite extensive research worldwide for nearly 50 years, the STH efficiency of these stable materials still falls short of the 10% target, as their charge transport properties and band gaps are not suitable for efficient light collection and conversion.

[0004] Organic-inorganic metal-halide perovskite materials have attracted significant attention as promising photovoltaic (PV) materials. They possess excellent charge transport properties and a tunable bandgap of 1.48–2.2 eV, which are essential for efficient photoelectrodes. These materials can theoretically achieve a high STH efficiency of 28.7%. However, PSK materials suffer from instability in aqueous electrolytes, posing a critical challenge for PEC applications. Despite this, various perovskite materials have been studied, but they exhibit low photocurrent densities. The two main reasons for the low efficiency or stability of PSK-based PEC systems are (i) the low activity or stability of the PSK photoactive layer itself, and (ii) inadequate passivation layers or electrocatalysts, which lead to poor performance in terms of charge separation, charge transfer, and water-splitting activity. In particular, lead (Pb)-containing materials in conventional PSKs can leach lead into the electrolyte during degradation, posing serious environmental problems.

[0005] For the practical application of PEC water splitting technology, in addition to the high STH efficiency and excellent stability in aqueous electrolytes as mentioned above, it is required to enlarge the photoanode area without a significant decrease in performance. Most of the large-area metal oxide photoanodes reported to date have shown much lower performance compared to small-sized photoanodes. For example, BiVO4 is a representative photoanode material, and it is used as a small-sized photoanode (0.1–0.3 cm 2 ) shows a high STH efficiency of 6-8%. However, large BiVO4 photoanodes (1-70 cm 2 ) exhibits a low STH efficiency of 0.1–3% due to the high resistivity of the fluorine-doped tin oxide (FTO) coated glass substrate and the non-uniform thickness of the BiVO4 layer.

[0006] For practical photoelectrochemical water splitting, the development of highly efficient, stable, and scalable photoelectrodes is essential. However, no photoelectrode satisfying all of the above requirements has yet been reported.

[0007]

[0008] The present invention aims to provide a perovskite photoanode for efficient photoelectrochemical water splitting.

[0009] The present invention aims to provide a photoanode having high efficiency and excellent stability for water oxidation.

[0010] The present invention aims to provide a large-area photoanode having high STH efficiency.

[0011] The present invention aims to provide a photoelectrochemical water splitting system in which a perovskite photoanode and a solar cell of the same size are connected.

[0012]

[0013] 1. A perovskite photoanode comprising: an oxygen generating section including a first lower electrode, a first electron transport layer formed on the first lower electrode, a perovskite first light-absorbing layer formed on the first electron transport layer, a first hole transport layer formed on the first light-absorbing layer, a first upper electrode formed on the first hole transport layer, a first Ni thin film layer formed on the first upper electrode, and an oxygen evolution reaction catalyst layer formed on the first Ni thin film layer; and a passivation section including a second lower electrode, a second electron transport layer formed on the second lower electrode layer, a perovskite second light-absorbing layer formed on the second electron transport layer, a second hole transport layer formed on the second light-absorbing layer, a second upper electrode formed on the second hole transport layer, and a second Ni thin film layer formed on the second upper electrode; wherein the first lower electrode and the second upper electrode are electrically connected.

[0014] 2. A perovskite photoanode in the above 1, wherein the first electron transport layer and the second electron transport layer include at least one selected from the group consisting of TiO2, SnO2, and ZnO.

[0015] 3. In the above 1, the first light-absorbing layer and the second light-absorbing layer are perovskite photoanode comprising a compound represented by the following chemical formula 1:

[0016] ABX3 [chemical formula 1]

[0017] In the formula, A is a methylammonium (MA) or formamidinium (FA) cation, and B is Pb 2+ , Sn 2+ , Ge 2+ , Cu 2+ , Ni 2+ , Co 2+ and Fe 2+ At least one divalent metal cation selected from the group consisting of, and X is a halogen anion.

[0018] 4. In the above 1, the first hole transport layer and the second hole transport layer are 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly(3-hexylthiophene) (P3HT), poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]](PCPDTBT) and A perovskite photoanode comprising at least one selected from the group consisting of 7-(9,9'-spirobi[fluoren]-2-yl)-N-(7-(9,9'-spirobi[fluoren]-2-yl)-9,9-dioctyl-9H-fluoren-2-yl)-N-(4-(9H-carbazol-9-yl)phenyl)-9,9-dioctyl-9H-fluoren-2-amine (CzPAF-SBF).

[0019] 5. A perovskite photoanode in the above 1, wherein the first upper electrode and the second upper electrode include at least one selected from the group consisting of gold (Au), silver (Ag), and aluminum (Al).

[0020] 6. A perovskite photoanode in the above 1, wherein the thickness of the first Ni thin film layer and the second Ni thin film layer is 0.003 to 100 μm.

[0021] 7. A perovskite photoanode, wherein the oxygen evolution reaction catalyst layer in the above 1 comprises at least one selected from the group consisting of NiFeOOH, NiOOH, and FeOOH.

[0022] 8. A perovskite photoanode further comprising an Ag layer between the first upper electrode and the first Ni thin film layer and between the second upper electrode and the second Ni thin film layer in the above 1.

[0023] 9. In the above 8, the Ag layer is a perovskite photoanode, which is a cured layer of an adhesive in which Ag-coated polymer particles are dispersed.

[0024] 10. A water splitting module comprising a perovskite photoanode according to 1 above; a cathode; and an aqueous electrolyte.

[0025] 11. A water splitting module including a plurality of photoanodes in the above 10.

[0026] 12. In the above 10, the water-splitting module is a basic electrolyte.

[0027] 13. A water splitting system comprising a water splitting module according to 10 or 11 above; and a solar cell electrically connected to the water splitting module.

[0028]

[0029] The perovskite photoanode of the present invention is stable in water, including a Ni thin film layer that blocks water intrusion.

[0030] The perovskite photoanode of the present invention can be directly immersed in water to photoelectrochemically decompose water and produce hydrogen.

[0031] The perovskite photoanode of the present invention can provide a voltage sufficient for water decomposition by including a passivation portion.

[0032] The Ag layer of the photoanode of the present invention can form an ohmic contact between the Ni thin film layer and the perovskite light-absorbing layer, thereby providing an interface for the oxygen evolution reaction (OER) and efficient charge transfer.

[0033] The perovskite photoanode of the present invention has a high photocurrent density.

[0034] The perovskite photoanode of the present invention does not leach lead.

[0035] The water splitting module of the present invention can exhibit high STH efficiency by including a large-area perovskite photoanode provided in multiple units.

[0036] The perovskite-based PEC water splitting system comprising a perovskite photoanode and a solar cell connected in parallel according to the present invention has a high STH efficiency.

[0037]

[0038] Figure 1 is a schematic cross-sectional view of an oxygen generating portion of a photoanode according to one embodiment of the present invention.

[0039] Figure 2 is a schematic cross-sectional view of a photoanode according to one embodiment of the present invention.

[0040] Figure 3 is a schematic diagram of a photoanode according to one embodiment of the present invention.

[0041] Figure 4 is a schematic diagram of a water decomposition module according to one embodiment of the present invention.

[0042] Figure 5 is a schematic conceptual diagram of a water decomposition module according to one embodiment of the present invention.

[0043] Figure 6 shows a photograph of FAPbI3 and the analysis results thereof according to one embodiment of the present invention.

[0044] FIG. 7 shows the structure and performance of a nip structure FAPbI3PV cell according to one embodiment of the present invention.

[0045] Figure 8 shows the band gap determined according to the Kubelka-Munk function.

[0046] Figure 9 shows the reproducible scans of the absorbance spectrum and the results of time-of-flight secondary-ion mass spectrometry (ToF-SIMS) analysis before and after stability testing of the FAPbI3 layer.

[0047] Figure 10 shows a schematic diagram of the bonding and interface for improving the stability of the metal-encapsulated FAPbI3 photoanode and a comparison of PEC performance.

[0048] Figure 11 shows the performance of a Ni foil encapsulated FAPbI3PV cell.

[0049] Figure 12 is a schematic diagram showing the manufacturing steps of a metal-encapsulated FAPbI3 photoanode.

[0050] Figure 13 shows the electrocatalytic performance of various oxygen evolution catalysts (OECs) loaded on Ni foil.

[0051] Figure 14 shows the device structure and PEC performance of the nip structure NiFeOOH / Ni / FAPbI3 photoanode.

[0052] Figure 15 shows the effect of various pH and OEC on the performance of NiFeOOH / Ni / FAPbI3 photoanode.

[0053] Figure 16 shows the PEC performance in two-electrode and three-electrode setups.

[0054] Figure 17 shows a band alignment diagram for a metal-metal bond.

[0055] Figure 18 shows the charge transfer and recombination kinetics of different metal ('Ni', 'Ti' and 'Ag') foils and their influence on the PEC performance of NiFeOOH / metal / FAPbI3 photoanode.

[0056] Figure 19 shows the stability analysis results of the NiFeOOH / Ni / FAPbI3 photoanode.

[0057] Figure 20 shows the stability and ion leaching analysis results of the FAPbI3 photoanode exposed to epoxy in a PEC reactor.

[0058] Figure 21 shows the surface changes by XPS analysis of the NiFeOOH / Ni / FAPbI3 photoanode during the first hour of reaction and before and after stability testing.

[0059] Figure 22 shows the XPS spectra of O 1s on the NiFeOOH layer / Ni foil before and after the stability test.

[0060] Figure 23 shows the results of energy dispersive X-ray spectroscopy (EDS) mapping analysis of a metal-encapsulated NiFeOOH / Ni / FAPbI3 photoanode.

[0061] Figure 24 is a cross-sectional FE-SEM image of a FAPbI3 thin film device.

[0062] Figure 25 shows a photoanode device according to one embodiment of the present invention having excellent long-term stability.

[0063] Figure 26 shows a schematic diagram of a NiFeOOH / Ni / FAPbI3 photoanode mini module for an unassisted PEC water splitting system, a large-area module using the same, and analysis results thereof.

[0064] Figure 27 shows a schematic diagram of a PEC panel reactor.

[0065] Figure 28 shows a photograph of an actual PEC panel reactor.

[0066] Figure 29 shows the analysis results of a PEC-PV system using a NiFeOOH / Ni / FAPbI3 photoanode and a FAPbI3PV cell.

[0067] Figure 30 is a schematic conceptual diagram of a water decomposition system according to one embodiment of the present invention.

[0068] Figure 31 shows the performance analysis results of each relevant cell in the NiFeOOH / Ni / FAPbI3-based large-cell photoanode and mini module.

[0069] Figure 32 shows a schematic diagram of a large NiFeOOH / Ni / FAPbI3 photoanode encapsulation(en) mini-module using a parallel-connected n × n array design.

[0070] Figure 33 shows a schematic diagram of the en-PEC mini module.

[0071] Figure 34 shows the performance analysis results of a large photoanode for a scalable PEC system.

[0072] Figure 35 shows the experimental setup for testing the en-PEC mini module used in the scalable PEC system.

[0073] Figure 36 shows a process flow diagram of a scalable PEC water splitting panel for solar H2 production.

[0074]

[0075] One embodiment of the present invention provides a perovskite photoanode, including: an oxygen generating portion including a first lower electrode, a first electron transport layer formed on the first lower electrode, a perovskite first light-absorbing layer formed on the first electron transport layer, a first hole transport layer formed on the first light-absorbing layer, a first upper electrode formed on the first hole transport layer, a first Ni thin film layer formed on the first upper electrode, and an oxygen evolution reaction catalyst layer formed on the Ni thin film layer; and a passivation portion including a second lower electrode, a second electron transport layer formed on the second lower electrode, a perovskite second light-absorbing layer formed on the second electron transport layer, a second hole transport layer formed on the second light-absorbing layer, a second upper electrode formed on the second hole transport layer, and a second Ni thin film layer formed on the second upper electrode.

[0076]

[0077] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. However, the following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the contents of the invention described above, serve to further understand the technical concept of the present invention. Therefore, the present invention should not be interpreted as being limited to the matters described in such drawings.

[0078] The terms “first”, “second”, “third”, “first end”, “other end”, “top surface”, “bottom surface”, “front”, “back”, “upper part”, “lower part”, etc. used in this application do not limit absolute positions or orders, but are used in a relative sense to distinguish different components or parts.

[0079]

[0080] <Gwanganode>

[0081] FIG. 1 schematically illustrates the layered structure of an oxygen generating portion of a perovskite photoanode according to one embodiment of the present invention.

[0082] The first lower electrode functions to transfer electrons generated in the perovskite light-absorbing layer to the outside. Any material that can be used as an electrode may be used for the first lower electrode without particular limitations. Examples of materials that can be used include indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and the like. Fluorine-doped tin oxide is more preferably used due to its economical nature.

[0083] The first electron transport layer transports electrons generated in the perovskite light-absorbing layer to the lower electrode.

[0084] In one embodiment of the present invention, the first electron transport layer may include at least one selected from the group consisting of TiO2, SnO2, ZnO, MgO, WO3, PbO, In2O3, Bi2O3, Ta2O5, BaTiO3, BaZrO3, and ZrO3. In a preferred embodiment, the electron transport layer of the present invention may include at least one selected from the group consisting of TiO2, SnO2, and ZnO. In a more preferred embodiment, the electron transport layer of the present invention may include TiO2.

[0085] In one embodiment of the present invention, the first perovskite light-absorbing layer absorbs externally irradiated light (e.g., sunlight) to generate electrons and holes.

[0086] As an exemplary embodiment, the first perovskite light-absorbing layer may include a compound represented by ABX3 [chemical formula 1]. In chemical formula 1, A is a methylammonium or formamidinium cation, and B is Pb. 2+ , Sn 2+ , Ge 2+ , Cu 2+ , Ni 2+ , Co 2+ and Fe 2+At least one divalent metal cation selected from the group consisting of, and X may be a halogen anion. In one embodiment, the perovskite light-absorbing layer of the present invention may include FAPbI3 or MAPbI3. In a preferred embodiment, the perovskite light-absorbing layer of the present invention may include FAPbI3.

[0087] In one embodiment of the present invention, the first hole transport layer transports holes generated in the perovskite light-absorbing layer upward.

[0088] In an exemplary embodiment, the first hole transport layer comprises 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly(3-hexylthiophene) (P3HT), poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]](PCPDTBT), and It may include at least one selected from the group consisting of 7-(9,9'-spirobi[fluoren]-2-yl)-N-(7-(9,9'-spirobi[fluoren]-2-yl)-9,9-dioctyl-9H-fluoren-2-yl)-N-(4-(9H-carbazol-9-yl)phenyl)-9,9-dioctyl-9H-fluoren-2-amine (CzPAF-SBF). In one embodiment, the first hole transport layer of the present invention may include Spiro-OMeTAD.

[0089] The first upper electrode of the present invention transfers holes generated at the lower portion to the upper portion.

[0090] In an exemplary embodiment, the first upper electrode may include, but is not limited to, at least one selected from the group consisting of gold (Au), silver (Ag), and aluminum (Al). In one embodiment, the metal layer of the present invention may include Au.

[0091] In one embodiment of the present invention, the first Ni thin film layer blocks water penetration, thereby preventing the perovskite light-absorbing layer from coming into contact with water. In addition, the Ni thin film layer can also prevent the lead component of the perovskite from being released to the outside.

[0092] In one embodiment, the thickness of the first Ni thin film layer may be 0.003 to 100 μm, preferably 10 to 50 μm, and more preferably 20 to 30 μm. Within this range, penetration of moisture or electrolyte into the perovskite can be effectively prevented.

[0093] In one embodiment of the present invention, the oxygen generation reaction catalyst layer decomposes water into oxygen, and at this time, holes transmitted from below are used.

[0094] In an exemplary embodiment, the oxygen evolution reaction catalyst may comprise at least one selected from the group consisting of NiFeOOH, NiOOH and FeOOH, and preferably comprises NiFeOOH.

[0095] In one embodiment of the present invention, an Ag (silver) layer may be additionally included between the first upper electrode and the first Ni thin film layer. The Ag layer may act as an ohmic contact medium to provide an interface for the oxygen evolution reaction and efficient charge transfer.

[0096] In an exemplary embodiment, the Ag layer may be a layer formed solely of Ag or a layer partially containing Ag.

[0097] The layer containing some Ag is not particularly limited in its shape or composition as long as it contains enough Ag to function as a conductive material. For example, it may have a structure in which Ag-coated particles are dispersed within the matrix.

[0098] In an exemplary embodiment, the Ag layer may be a cured layer of an adhesive having Ag-coated polymer particles dispersed therein.

[0099] Polymer particles coated with Ag may be formed using, as raw materials, thermosetting polymer resins such as phenol resin, urea resin, melamine resin, fluororesin, polyester resin, epoxy resin, silicone resin, polyimide resin, polyurethane resin, propylene resin, and polyolefin resin; and thermoplastic polymer resins such as polyethylene resin, polypropylene resin, polybutylene resin, poly(meth)acrylate resin, methylene resin, polystyrene resin, acrylonitrile-styrene resin, acrylonitrile-styrene-butadiene resin, vinyl resin, divinylbenzene resin, polyamide resin, polyester resin, polycarbonate resin, polyacetal resin, pyronoma resin, polyether sulfone resin, polyphenyloxide resin, polyphenylene sulfide resin, polysulfone resin, and polyurethane resin.

[0100] Adhesives include acrylic adhesives, epoxy adhesives, and silicone adhesives.

[0101] In one embodiment of the present invention, the passivation portion functions to provide a potential difference required for oxygen generation.

[0102] In an exemplary embodiment, the passivation portion may have the same laminated structure as the oxygen generation portion, except for the oxygen generation reaction catalyst. Therefore, descriptions of the lower electrode, electron transport layer, light absorption layer, hole transport layer, upper electrode, and Ni thin film layer of the passivation portion are omitted to avoid duplication.

[0103] In one embodiment of the present invention, the lower electrode of the oxygen generating unit is electrically connected to the upper electrode of the passivation unit. Electrons generated in the oxygen generating unit move to the upper electrode of the passivation unit and combine with holes generated in the passivation unit, thereby maintaining electrical flow.

[0104] The oxygen generation unit and the passivation unit can be formed on a substrate, and there is no limitation on the substrate as long as it is transparent and can transmit light. For example, a glass substrate can be used.

[0105] As illustrated in FIG. 12a, the photoanode according to one embodiment of the present invention may have its side sealed with a sealant. Any sealant known in the art, such as epoxy resin, may be used without particular limitation.

[0106]

[0107] Water Decomposition Module

[0108] FIG. 4 is a schematic diagram of a water decomposition module according to one embodiment of the present invention, and FIG. 5 is a schematic conceptual diagram of a water decomposition module according to one embodiment of the present invention.

[0109] A water splitting module according to one embodiment may include a photoanode, a cathode, and an aqueous electrolyte.

[0110] The photoanode is applied to the photoanode according to the present invention.

[0111] In exemplary embodiments, the photoanode may be provided singly or in plurality.

[0112] The photoanode according to the present invention can be connected to a cathode through wiring.

[0113] The cathode may be used without any particular limitation as long as it is formed of a material that can be used as a water splitting electrode together with the photoanode of the present invention, and may include, for example, one or more selected from the group consisting of platinum (Pt), ruthenium, rhodium, palladium, osmium, and iridium, but is not limited thereto. In one embodiment, the cathode of the present invention may include Pt.

[0114] The aqueous electrolyte may be a basic electrolyte, an acidic electrolyte, or a neutral electrolyte. The basic electrolyte may be an aqueous solution of a basic compound such as NaOH, KOH, or Na2SO3. The acidic electrolyte may be an aqueous solution of an acidic compound such as HCl or H2SO4. The neutral electrolyte may be an aqueous solution of water (H2O), potassium phosphate (KPi), or the like. Preferably, a basic electrolyte may be used.

[0115]

[0116] Water Decomposition System

[0117] FIG. 29a is a schematic diagram of a water decomposition system according to one embodiment of the present invention, and FIG. 30 is a schematic conceptual diagram of a water decomposition system according to one embodiment of the present invention.

[0118] A water splitting system according to one embodiment of the present invention includes a structure (PEC-PV) in which a water splitting module according to one embodiment of the present invention and a solar cell are combined.

[0119] In an exemplary embodiment, the solar cell may have the same structure as the laminated structure from the lower electrode to the upper electrode of the oxygen generating unit. In this case, the component of the solar cell corresponding to the lower electrode of the oxygen generating unit functions as a front electrode that transmits light from the solar cell and is electrically connected to the cathode of the water decomposition module through wiring. In addition, the component of the solar cell corresponding to the upper electrode of the oxygen generating unit functions as a rear electrode and is connected to the photoanode of the water decomposition module through wiring.

[0120] In an exemplary embodiment, electrons generated in the light-absorbing layer (perovskite) of the solar cell move through wiring to the cathode of the water-splitting module and are used to decompose water and generate hydrogen, and holes generated in the light-absorbing layer (perovskite) move to the photoanode and combine with electrons generated in the photoanode.

[0121]

[0122] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The examples and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the examples are possible within the scope and technical idea of ​​the present disclosure, and it is also natural that such changes and modifications fall within the scope of the appended claims.

[0123]

[0124] Example

[0125] (1) Fabrication of perovskite (FAPbI3) photovoltaics (PV) cells

[0126] Figure 1 shows a NiFeOOH / Ni / FAPbI3 photoanode, where the NiFeOOH-deposited 'Ni' foil encapsulates the FAPbI3 layer to protect it from moisture permeation, and the 'Ag' paste serves as an ohmic contact medium between the 'Au' layer and the 'Ni' foil to provide an interface for oxygen evolution reaction and efficient charge transfer.

[0127] Figure 4 shows a perovskite-based encapsulated PEC mini-module (2 × 2 array, 30.8 cm) for large-area unassisted solar water splitting. 2 ) is shown as a schematic diagram. Mini modules (2 × 2 array, 30.8 cm) are positioned inside the solar water splitting panel reactor filled with electrolyte. 2 ) to develop a large-scale NiFeOOH / Ni / FAPbI3 photoanode (2-cell, 7.68 cm 2 ) were fabricated by connecting 2 × 2 arrays in parallel. A large-scale photoanode (2-cell, 7.68 cm 2 ), only one of the two NiFeOOH / Ni foils participates in oxygen evolution, and the other acts as a protective layer (passivation) for FAPbI3.

[0128]

[0129] The perovskite solar cell (PSC, Fig. 6a) of this embodiment uses FAPbI3 as a light absorber. The UV-vis spectrum of FAPbI3 (Fig. 6b) shows absorption in a broad wavelength range of 400-800 nm, and has a photoluminescence emission peak at 825 nm (Fig. 6c), which is interpreted to have a direct bandgap of 1.55 eV according to the Tauc plot (Fig. 7c) and the Kubelka-Munk function (Fig. 8). The FAPbI3 layer is crystalline and exhibits an X-ray diffraction pattern corresponding to pure cubic α-FAPbI3 without impurities such as PbI2 and δ-FAPbI3 (Fig. 6d). The peak (111) at 24.4° corresponds to the plane of α-FAPbI3, which is relatively more stable to moisture than other planes.

[0130] The FAPbI3 perovskite PV of this example was fabricated with a multilayered nip structure of glass / FTO / TiO2 / FAPbI3 / 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) / gold (Au), as shown in the cross-sectional scanning electron microscope (SEM) image in Fig. 7a. The planar surface morphology of the FAPbI3 layer in Fig. 7b shows a uniformly distributed, dense, and crystalline thin film with a homogeneous and large particle size, which is a characteristic of a PSC with high power conversion efficiency (PCE). The inset in Fig. 7c illustrates the appropriate band alignment of each layer. Therefore, the present inventors have demonstrated a high external quantum efficiency (EQE) of >90% and a peak current of 23.4 mA cm over a wide absorption range of 350-850 nm. -2 Integrated photocurrent density (J sc) was prepared (Fig. 7d). The synthesis method and detailed manufacturing procedure are described in the <Manufacturing Method> section below.

[0131]

[0132] Simulated (AM 1.5G) 1-sun conditions (100 mW cm -2 ) The high performance of the FAPbI3PV cell of the present invention under the illumination of ) is demonstrated by the photocurrent density-voltage (JV) curve and key parameters of the insert table in Fig. 7e: J sc = 24.52 mA cm -2 , open circuit potential (V oc ) = 1.16 V, charge factor (FF) = 82.63%, PCE = 23.47%. J measured from the device sc (Fig. 7e) Integrated J from EQE sc(Fig. 7d) is very close to that in Fig. 7d. In addition, the fully encapsulated FAPbI3PV cell was proven to be very stable without degradation in air under maximum power point (MPP) conditions for 120 h (Fig. 7f). This was confirmed by the reproducible scan of the absorbance spectrum (Fig. 9a) and also by the time-of-flight secondary-ion mass spectrometry (ToF-SIMS) analysis of the FAPbI3 layer (Figs. 9b-j). Fig. 9a shows a repeat scan for the absorbance. Figs. 9b-9d show the ToF-SIMS results of the pure FAPbI3 layer and the ETL / FAPbI3 / HTL / Au thin film device before and after the stability test, respectively. Figures 9e to 9j show 3D images of the pure FAPbI3 layer (Figures 9e and 9h), 3D images of the ETL / FAPbI3 / HTL layer (Figures 9f and 9i), and 3D images of the 'Au' layer (Figures 9g and 9j), which were measured before (Figures 9e to 9g) and after (Figures 9h to 9j) the stability test.

[0133]

[0134] (2) Fabrication of perovskite (FAPbI3) photoanode

[0135] The inventors of the present invention completely blocked the permeation of the electrolyte by attaching a 25 μm thick 'Ni' metal foil to the FAPbI3 thin film (see the method section for detailed procedures).

[0136] The Ag paste acted as a crucial ohmic bonding metal between the Ni foil and the FAPbI3 layer without significantly degrading the performance (Fig. 10). After confirming that similar PV performance was achieved even after Ni encapsulation (Fig. 11), NiFeOOH, as an oxygen evolution reaction (OER) catalyst, was deposited on the 'Ni' foil by drop-casting Ni and Fe precursors to fabricate a metal-encapsulated FAPbI3 (denoted as NiFeOOH / Ni / FAPbI3) photoanode (Fig. 12).

[0137] Electrochemical performance of NiFeOOH / Ni foil loaded with noble metal oxide (IrO) on 'Ni' foil x and RuO x ) was much better than the electrochemical performance of IrO loaded on Ni foil (Fig. 13). The NiFeOOH / Ni electrocatalyst x and RuO x Compared to the electrocatalyst, it exhibited a higher cathodic onset potential due to a lower Tafel slope and lower charge transfer resistance in 1 M KOH (Figs. 13a to 13c). Since NiFeOOH was directly deposited on the 'Ni' foil by drop-casting the Ni-Fe precursor solution, the NiFeOOH / Ni interface was IrO according to the Nyquist plot of electrochemical impedance spectroscopy (EIS, Fig. 13c). x / Ni or RuO x / Ni interface exhibited superior charge transport. In addition, the NiFeOOH / Ni foil electrode was stable in 1 M KOH for 80 h (Fig. 13d) without any significant change in surface morphology before and after the stability test (Fig. 14c before stability test and 13d after stability test).

[0138] Next, the PEC water oxidation performance of the NiFeOOH / Ni / FAPbI3 photoanode (Fig. 14) was measured in 1 M KOH (pH 14) under 1-sun illumination in a three-electrode setup with the photoanode, Hg / HgO (1 M NaOH), and Pt wire as the working, reference, and counter electrodes, respectively. The photocurrent density (J) of the NiFeOOH / Ni / FAPbI3 photoanode ph ) is 1.23 V RHE 22.82 mA cm at -2 It showed a very high value as (Fig. 14b).

[0139] The performance was also measured for the Ni / FAPbI3 photoanode without catalyst and in the sulfite oxidation (Fig. 15a). The JV characteristics of the NiFeOOH / Ni / FAPbI3 photoanode according to the present invention (Fig. 15a) in the electrolyte with and without sulfite (i.e., sulfite and water oxidation, respectively) were V on and photocurrent density were similar. The surface charge separation (%ηsurface) efficiency of the NiFeOOH / Ni / FAPbI3 photoanode was >94%, while that of Ni / FAPbI3 was 0.75 V. RHE , which was only 33% (Fig. 15b), further demonstrating that NiFeOOH as an OER catalyst enables highly efficient surface charge separation.

[0140] We also determined the performance of the NiFeOOH / Ni / FAPbI3 photoanode in electrolytes of different pHs (Fig. 15c). Compared with acidic (0.5 M H2SO4, pH~1) and near-neutral (1 M KPi, pH~7) media, the NiFeOOH / Ni / FAPbI3 photoanode exhibited the highest performance in a basic solution (1 M KOH, pH~14), confirming that the Ni-encapsulated FAPbI3 photoanode containing NiFeOOH as a catalyst exhibited the best performance in basic electrolytes.

[0141] The present inventors also measured the performance of the NiFeOOH / Ni / MAPbI3 photoanode. 1.23 V RHE 18.72 mA cm -2 J of ph was measured, which is a lower value than the photoanode of the present invention (Fig. 14b). 1.23 V of the NiFeOOH / Ni / FAPbI3 photoanode RHE The incident photon-to-current efficiency (IPCE) in the range of 400–800 nm was close to 87% for photons, and the integrated photocurrent value was 22.56 mA cm -2 , which is the value (22.82 mA cm) in the JV measurement (Fig. 14b). -2 ) were consistent with those of the MAPbI3-based photoanodes. These IPCE results also demonstrated that the improved performance of NiFeOOH / Ni / FAPbI3 over a wider optical range was due to its smaller bandgap (Fig. 14c). The NiFeOOH / Ni / FAPbI3 photoanode exhibited the highest photovoltage (V ) of 0.99 V among all single semiconductor-based photoanodes reported so far. ph ) was shown, which was 0.41 V RHE Low V of on This high photocurrent density and low V on 0.765 V in a 3-electrode setup RHE resulted in a high ABPE of 7.93% (Fig. 16a and b). Similarly, 0.728 V vs. counter electrode (V CE ) was obtained in a two-electrode setup with an ABPE of 7.31% (Fig. 16c and d).

[0142] 0.85 V corresponding to the maximum %ABPE RHEThe gas evolved from the NiFeOOH / Ni / FAPbI3 photoanode at an applied potential was quantified by gas chromatography (GC), which showed an FE of >97% for both H2 and O2 evolution (Fig. 14d), and the gas of O2:H2 (1:2 molar ratio) was continuously generated without any decrease (Fig. 14e). This indicates that the observed photocurrent is entirely due to the water splitting reaction. Therefore, the NiFeOOH / Ni / FAPbI3 photoanode of the present invention has the best V among all PSK-based photoanodes, metal oxide photoanodes, silicon photoanodes, and organic-based photoanodes reported so far, as summarized in Fig. 14f. on , it has been proven to have excellent stability as well as %ABPE.

[0143]

[0144] (3) Understanding the causes of high efficiency and stability of NiFeOOH / Ni / FAPbI3 photoanode

[0145] a) The choice of metal foil was also found to be important because 'Ni' foil encapsulation not only protects the FAPbI3 layer from moisture penetration but also promotes efficient photogenerated hole transport to the NiFeOOH catalyst without recombination for efficient water oxidation. For example, the present inventors studied the effects of various metal foils ('Ni', 'Ag', and 'Ti') on the kinetics of charge transport and water oxidation, and the results are shown in Figs. 17 and 18. The NiFeOOH / Ni foil was the most suitable metal foil to be applied on the FAPbI3 photoanode in terms of efficiency and stability. Compared with the Ag and Ti foils, the NiFeOOH / Ni foil showed improved charge transfer kinetics for OER, higher %η. surface , earlier turn-on voltage (V on ), higher photovoltage (V ph , Fig. 18f), and had better stability in base solutions.

[0146]

[0147] b) The inventors also verified the stability by repeatedly performing 25 scans and confirming that each scan showed almost the same performance (Fig. 19a). Voltage-dependent chronoamperometry under continuous light irradiation (Fig. 19b) and voltage-dependent chronoamperometry under discontinuous light irradiation (Fig. 19c) also showed the stability of the photoanode of the present invention at different potentials. The stability of the NiFeOOH / Ni / FAPbI3 photoanode was measured by X-ray photoelectron spectroscopy (XPS) on the NiFeOOH / Ni / FAPbI3 photoanode and by inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements on the electrolyte before and after the stability test (Figs. 19-21). The measurement results indicate that the reconstitution of NiFeOOH occurred during the first hour of the reaction, but the NiFeOOH / Ni / FAPbI3 photoanode became stable after 1 hour. Energy-dispersive X-ray spectroscopy (EDS) mapping and cross-sectional SEM images of the NiFeOOH / Ni / FAPbI3 photoanode further showed a uniform element (Ni, Fe, O) distribution with no observable change in the thickness of each layer before and after stability testing (Figs. 23-24).

[0148]

[0149] c) Dissolved 'Pb' was observed in the electrolyte from 43 h (Fig. 20c). As discussed above, it was found that FAPbI3 was photostable and the NiFeOOH electrocatalyst itself was also stable (Figs. 7f, 9, and 20-21). Therefore, it was speculated that the insulating epoxy could be the cause of the observed Pb degradation. To verify the speculation, a new reactor was designed in which the insulating epoxy was not exposed to the electrolyte (Fig. 25a). In the newly designed reactor, the NiFeOOH / Ni / FAPbI3 photoanode remained stable for 3 days (Fig. 25b). In addition, ICP-OES measurements were performed at reaction times of 5, 10, 30, 43, 50, and 70 h to determine the possibility of leaching of 'Ni', 'Fe' ions, and especially 'Pb' (Fig. 25c). No leaching of 'Ni', 'Fe' or especially 'Pb' was observed during the stability test, confirming that the epoxy was the main cause of Pb dissolution after 43 hours in the previous stability test (Fig. 20a).

[0150]

[0151] (4) Manufacturing of scalable PEC-PV systems

[0152] The NiFeOOH / Ni / FAPbI3 photoanode and Pt cathode (Pt wire) were immersed in the electrolyte inside the PEC reactor, and another FAPbI3PV cell was installed in parallel (side by side) outside the electrolyte as shown in Fig. 29a. A schematic and photograph of the PEC panel reactor are shown in Figs. 27 and 28.

[0153]

[0154] The performance of the PEC-PV system was measured in 1 M KOH (pH 14) using a two-electrode setup. As shown in Fig. 26b, the operating point of the PEC-PV was determined at the intersection of the JV curves of the two devices: 16.88 mA cm -2 J of op Wow 0.91 V CE V of op, which corresponds to an STH efficiency of 10.38% (results in a 3-electrode setup are shown in Fig. 29). Under unassisted conditions (0 V) in Fig. 26c CE ) and the actual generation of H2 and O2 (299.7 and 150.1 μmols cm for 1 hour, respectively). -2 ) was determined to have a STH efficiency of 9.8%. The STH efficiency was also calculated using Faraday's law of electrolysis, which was consistent with the efficiency at the operating point described above. Figure 26d shows the metal-encapsulated perovskite-based en-PEC mini-module (2 × 2 array, 30.8 cm) installed in one PEC panel reactor. 2 ) is a schematic diagram. Figure 26 e shows the operating JV curves of the unassisted large-cell photoanode showing the effect of different active cell regions on the PEC performance. Figure 26 f shows the operating JV curves of the unassisted large-cell photoanode under unassisted conditions (0 V CE ) measured in a two-electrode setup at a large photoanode (2-cell, 7.68 cm 2 ) shows the Jt curve of the en-PEC mini module (2 × 2 array, 30.8 cm) in the PEC panel reactor. Figure 26 g shows the Jt curve of the en-PEC mini module (2 × 2 array, 30.8 cm) in the PEC panel reactor. 2 ) is an image of the 1 × 2 array multi-reactor (30.8 cm) of the en-PEC mini module, and Fig. 26 h 2 × 2 = 61.6 cm 2 ) is an image of the 2 × 2 array multi-reactor (30.8 cm) of the en-PEC mini module. 2 × 4 = 123.2 cm 2 ) is an image of <1 cm using mini module and module scale demo. 2 >100 cm 2The STH efficiency of a large-scale PEC system with an active irradiance region of . The perovskite-based PEC-PV system of the present invention has the highest STH efficiency of 9.8% among all the conventional PSK photoanode-based or metal oxide (or nitride)-based PEC-PV systems reported for unassisted water splitting.

[0155]

[0156] The present inventors used a NiFeOOH / Ni / FAPbI3 photoanode with a thickness of 0.25 cm 2 123.2 cm at 2 It has been gradually expanded to include and has proven its performance not only in the laboratory but also under outdoor solar conditions.

[0157]

[0158] The number of cells required to fabricate a large-area NiFeOOH / Ni / FAPbI3 photoanode mini module is disclosed in Fig. 31. 1.23 V RHE One large-scale photoanode (3.84 cm) in 2 ) has a photocurrent density of 20.4 mA cm -2 Small cell (0.25 cm) 2 ) photocurrent density (1.23 V RHE 22.8 mA cm at -2 ) was very similar to that of the photovoltaic cell, and only about 10% was reduced due to the enlargement of the unit cell area (Figs. 31b and 31e). To obtain sufficient photovoltage for unassisted PEC water splitting, the inventors used two unit cells (2 × 3.84 cm 2 ) consisting of a large photoanode (2-cell, 7.68 cm 2 ; Fig. 32-33) was manufactured (Fig. 26 e). This immersed large photoanode (2-cell, 7.68 cm 2 ) is a two-electrode setup without additional FAPbI3PV cells at 0 V. CE 7.43 mA cm -2 The photocurrent density of the large photoanode (2-cell, 7.68 cm) was shown (Fig. 26 de, Fig. 31 ce).2 ), it should be noted that only one of the two NiFeOOH / Ni foils actively participates in OER, while the other mainly functions as a protective layer for the FAPbI3PV cell to supply bias voltage (as shown in FIGS. 4 and 33).

[0159]

[0160] As the number of series connections increased from 2 to 5 cells, the photovoltage increased while the photocurrent density decreased (Fig. 31c-e). However, for large photoanodes (2-cell, 7.68 cm 2 ) is -1.0 V CE V of on Because it exhibited sufficient photovoltage to decompose water, a 2-cell was selected as the basic unit of a large-cell photoanode for large-area application (Fig. 31d). This large-size photoanode (2-cell, 7.68 cm 2 ) is 135.4, 67.7 μmol cm -2 h -1 showed gas production rates of H2 and O2, which corresponds to an STH efficiency of 8.9% (Fig. 26f and Fig. 34c). In addition, the en-PEC mini module (2 × 2 array, 30.8 cm 2 ) are connected in parallel to produce an active area of ​​30.8 cm 2 extended to (Figs. 33 and 34). en-PEC mini module (2 × 2 array, 30.8 cm 2 ) is 213 mA (6.91 mA cm -2 , 129.8 and 65.5 μmol cm corresponding to the absolute photocurrent and STH efficiency of 8.54% (Fig. 34d). -2 h -1 shows the H2 and O2 produced at a ratio of (Fig. 34d and e). This large-area step (7.68 -> 30.8 cm 2 ) the saturation photocurrent density was reduced by only 6% (Fig. 26e, and Figs. 34a and b).

[0161] 1 × 2, 2 × 2 array multi-reactors (total areas of 61.6 and 123.2 cm, respectively) 2 ) were further expanded by increasing the number of reactors in an array (Figs. 26h and i, and Figs. 35c-i). These large-area modules (30.8-123.2 cm 2 ) had an STH efficiency of 8.5% for 2 h and >128.9 and >64.5 μmol cm -2 h -1 showed the gas productivity ratio of H2 and O2 (Fig. 34e-g). Therefore, each en-PEC mini module (2 × 2 array, 30.8 cm 2 ) could maintain high STH efficiency even with increased area (single small cell, large cell, multi-cell, and multi-reactor approaches; Fig. 34h) because they had similar performance. In addition, a 2 × 2 array multi-reactor water splitting panel (123.2 cm 2 ) has the advantage of allowing simultaneous continuous flow of electrolyte and collection of generated gas in separate reservoirs (Fig. 36). This is the first large-area PEC system using a metal-encapsulated PSK photoanode, and the STH efficiency of more than 8.5% achieved by the present invention is >1 cm 2 This is the highest efficiency among all reported conventional large-area photoanodes (Fig. 26j). Since high STH efficiency and excellent stability were maintained in the large-area photoanode, the Techno-Economic Analysis (TEA) showed that the overall PSK-based en-PEC system is cost-competitive compared to PSK-based PV-EC (Fig. 34).

[0162]

[0163] In summary, the present inventors applied FAPbI3 after encapsulating and stabilizing NiFeOOH electrocatalyst loaded with Ni foil to fabricate a photoanode for full PSK-based PEC water splitting. The NiFeOOH / Ni / FAPbI3 photoanode exhibited a 1.23 V / V voltage under simulated 1-sun irradiance, respectively. RHE 22.82 mA cm at -2 and 0.728 V CE The photoanode was stable for 3 days in aqueous solution under continuous sunlight irradiation without any signs of degradation, indicating that water did not penetrate into the FAPbI3 layer at all. Furthermore, unassisted solar H2 production was achieved by coupling the NiFeOOH / Ni / FAPbI3 photoanode in parallel with another FAPbI3PV cell (PEC-PV), recording the highest STH efficiency among all reported conventional PSK-based photoanodes. Furthermore, by increasing the unit cell size, increasing the number of cells (multi-cell approach), and increasing the number of reactors (multi-reactor approach), the NiFeOOH / Ni / FAPbI3 photoanode was further improved from 0.25 to 123.2 cm without a significant decrease in STH efficiency (less than 15%). 2 (500 times larger). As a result, it was demonstrated that the high STH efficiency of small-cell can be maintained in large-cell photoanodes.

[0164]

[0165] <Manufacturing method>

[0166] (1) Materials

[0167] All chemicals, such as Ni(NO3)2·6H2O (Sigma-Aldrich, 99.99%), Fe(NO3)3·9H2O (Kanto Chemicals > 98.5%), and electrolytes (1 M KOH, 0.5 M H2SO4), were used without further processing as obtained from their respective manufacturers. Electrolytes, such as 1 M Na2SO3 (pH 9.3) and 1 M KPi (pH 7), were prepared and used by the inventors.

[0168]

[0169] (2) Synthesis of FAPbI3 perovskite ink

[0170] Formamidinium iodide (FAI) was synthesized as a white powder by reacting 20 mg of formamidine acetate salt (99%, Alfa Aesar) with 30 mL of aqueous HI solution (57 wt%, Sigma-Aldrich) in a 250 mL flask at 60°C and 1 mbar with stirring for 1 h. The precipitated product was obtained by evaporation at 60°C for 1 h. The FAI product was dissolved in ethanol, mixed with diethyl ether, recrystallized, and finally dried in a vacuum oven at room temperature for 24 h. 19.5 mmol of the synthesized mixture of FAI and PbI2 (99.99%, TCI chemicals) (1:1 molar ratio) was added to 11 mL of 2-methoxyethanol (2-ME, anhydrous 99.8%, Sigma-Aldrich) in a 70 mL vial and continuously stirred to synthesize black powder of formamidinium triiodide (FAPbI3). The mixed solution was heated to 120°C and precipitated by the retrograde method. The filtered FAPbI3 powder was baked at 150°C for 30 min. FAPbI3 (889 mg mL -1 ) ink was prepared in a binary solvent of dimethylformamide (Sigma-Aldrich) and dimethyl sulfoxide (Sigma-Aldrich) at an 8:1 v / v ratio, which was taken as an appropriate ratio to achieve controlled fabrication of FAPbI3PV cells. Spiro-OMeTAD / chlorobenzene (90 mg mL -1 ) solution was added to 39.5 μL of 4-tert-butylpyridine (TBP), 23 μL of Li-bis(trifluoromethanesulfonyl)imide (Li-TFSI) / acetonitrile (520 mg mL -1 ) and 10 μL of Co-TFSI / acetonitrile (375 mg mL -1 ) was prepared from a mixture of

[0171]

[0172] (3) Fabrication of FAPbI3PV cells

[0173] A FAPbI3PV cell with a nip structure was fabricated. A dense TiO2 hole-blocking layer (bl-TiO2) was deposited on a 2.5 cm × 2.5 cm fluorine-doped tin oxide (FTO) (TEC 8; Pilkington, 10-15Ω cm -2, Sigma-Aldrich) was coated by spray pyrolysis deposition of 20 mM titanium diisopropoxide bis(acetylacetonate)-Ti(acac)2 (75 wt% in isopropyl alcohol, IPA, Sigma-Aldrich) at 450°C. This layer was deposited to prevent direct contact between the FTO and the hole transport layer (HTL). A 200 nm thick mesoporous TiO2 (mp-TiO2 with a particle size of 50 nm, anatase phase) was spin-coated on the bl-TiO2 / FTO substrate at 1500 rpm for 40 s using TiO2 paste (SC-HT040, ShareChem) dissolved in a mixture of 2-ME:terpineol (3.5:1 w / w). The film was calcined at 500°C for 1 h to remove organic components. The FAPbI3 layer was spin-coated on mp-TiO2 / bl-TiO2 / FTO. The FAPbI3 layer was first heat-treated at 150°C for 10 min and then annealed at 100°C for 10 min. For surface passivation of the FAPbI3 layer, 15 mM phenethyl ammonium iodide-PEAI (98%, Greatcell Solar) dissolved in IPA (Sigma-Aldrich) was spin-coated at 5000 rpm. The surface-treated film was dried in a vacuum oven for 24 h or annealed at 100°C for 5 min, depending on the passivation conditions. For HTL, a Spiro-OMeTAD (99%, Sigma-Aldrich) solution was spin-coated at 3000 rpm for 30 s. Finally, indium was bonded onto the FTO portion (lower electrode) for additional ohmic contact, and a gold counter electrode (upper electrode) was deposited using thermal evaporation. The related photograph is shown in Fig. 6.

[0174]

[0175] (4) Fabrication of NiFeOOH / Ni foil electrode

[0176] Ni foils (10, 25, 50, and 100 μm, >99% metal Alfa Aesar) of required sizes (0.5 cm × 0.5 cm, 1 cm × 1 cm, and 6.5 cm × 0.7 cm) were re-treated with deionized water, ethanol, and deionized water for 10 min each under bath sonication. NiFeOOH electrocatalysts were prepared by the precipitation metal nitrate precipitation (PMND) method. 0.02 M Ni and Fe precursor solutions were prepared by dissolving 0.0290 g of Ni(NO3)2·6H2O (Sigma-Aldrich, 99.999%) and 0.0404 g of Fe(NO3)3·9H2O (Kanto Chemicals, >98.5%) precursors in 5 mL of 2-ME. The two precursor solutions were mixed in a molar ratio of 1:1, sonicated for 10 minutes and stirred for 60 minutes at room temperature. To prepare a single metal reference catalyst, 0.02 M NiOOH or FeOOH inks were prepared, respectively. Electrodes were prepared using each catalyst ink solution. 10 μL cm -2 The ink solution was drop-casted onto treated Ni foil substrates of various sizes. The solution was dried in an oven at 60°C for 5 min, and the electrocatalyst was deposited on the substrate by immersing it in a 1 M KOH solution for 10 s. The residual KOH on the electrode surface was rinsed with deionized water.

[0177]

[0178] (5) RuO x / Ni foil and IrO x / Manufacture of Ni foil electrode

[0179] To prepare 0.02 M of Ru-based electrocatalyst and Ir-based electrocatalyst inks, 0.041 g of RuCl3·xH2O (Sigma-Aldrich 99.9%) and 0.0947 g of Na2IrCl6·6H2O (Sigma-Aldrich 99.9%) were added to 10 mL of acetylacetone. 10 μL cm of these solutions -2The ink was loaded onto treated Ni foils (0.5 cm × 0.5 cm) and dried in an oven at 80°C for 20 min. The films were annealed in a furnace at 500°C for 1 h to obtain metal oxide films.

[0180]

[0181] (6) Preparation of Pt cathode

[0182] A Pt solution was prepared using 400 μL of H2PtCl6 (Sigma-Aldrich, 8 wt%) and 2800 μL of ethanol. 10 μL cm of this solution -2 FTO or Ni foam electrodes (up to 30.8 cm) treated with ink 2 ) and then final annealing was performed at 450°C for 1 hour.

[0183]

[0184] (7) Fabrication of NiFeOOH / Ni / FAPbI3 photoanode

[0185] The fabricated FAPbI3PV cell was used to fabricate a photoanode according to the detailed fabrication steps illustrated in Figures 12a-b. A Ni foil (25 μm thick, 99% metal, Alfa Aesar) was physically attached to the Au layer (top electrode on the hole-transport side) using Ag paste. Here, the Ag paste served as an ohmic contact mediator between the Au layer and the Ni foil to provide an electrical interface and efficient charge transfer for OER on the Ni foil. The bottom electrode (electron transport toward the FTO side) was physically connected to a copper wire for further testing. The entire NiFeOOH / Ni / FAPbI3 photoanode was secured using a two-component epoxy adhesive (JB Weld, USA) and dried overnight at room temperature. 10 μL of NiFeOOH ink (Ni:Fe in a 1:1 ratio) as the OEC was drop-casted onto the Ni foil, dried for 5 min, and then immersed in a 1 M KOH solution for 10 s. >1 cm as in Fig. 12b-d 2The same method was applied to fabricate photoanodes for large-area cells.

[0186]

[0187] (8) Manufacturing of FAPbI3PV modules

[0188] On pre-patterned and cleaned FTO substrates measuring 7 cm × 7 cm, bl-TiO2 and mp-TiO2 layers were deposited using the spray pyrolysis described above. The FAPbI3 precursor was mixed with 2-ME and 1-cyclohexyl-2-pyrrolidone. In addition, 5% MAPbBr3 was added to the FAPbI3 precursor ink to improve the crystal orientation of the FAPbI3PV cell and enhance the performance of the large-area device (FAPbI3). 0.95 (MAPbBr3) 0.05 A 0.83 M solution of FAPbI3 was deposited. To fabricate mini-modules without using laser scribing, FAPbI3 ink was deposited on a 7 cm × 7 cm mp-TiO2 layer at a thickness of 25 mm s. -1 Bar-coating was performed at a speed of 160 L min with a gap of 0.27 mm between the substrate and the bar. Then, an air knife was used to coat the substrate at a speed of 160 L min. -1 Continuous nitrogen gas blowing was performed. Then, the FAPbI3 layer was annealed at 150°C and 100°C for 15 min, respectively. For surface passivation of the FAPbI3 layer, 6 mM acetylcholine bromide in 2-propanol was added at a flow rate of 30 mm s -1 The bar-coating was performed at a speed of . After spin-coating the HTL, the Au layer was deposited using a thermal evaporator.

[0189]

[0190] (9) Production of en-PEC modules

[0191] To fabricate the metal-encapsulated FAPbI3 photoanode module, we used a novel method to attach the Ni foil to the Au back contact. Specifically, to provide proper electrical contact between the Ni foil and the top electrode (Au layer), an acrylic-based (Loctite 401, Henkel) adhesive mixed with Ag-coated polymethyl-methacrylate (PMMA) particles (0.5 wt% PMPMMS-AG-1.53, Cospheric, 45-53 micron sized PMMA particles coated with a 250 nm thick Ag layer) was uniformly pasted onto the Au layer and then dried at room temperature for 10 min. This adhesive played two roles: (i) applying a large Ni foil strip (3.84, 7.68 cm) onto the active cell, 2 ) to provide proper adhesion of the FAPbI3 layer, (ii) to protect the FAPbI3 layer from direct contact of the epoxy with the PMMA polymer (see Fig. 33). Finally, the bottom electrode was physically connected with a copper wire. The entire module of the Ni / FAPbI3 photoanode (Fig. 33) was secured using a two-component epoxy adhesive (JB weld, USA) and dried overnight at room temperature. For testing, 10 μL cm of NiFeOOH ink as OEC -2 was drop-casted onto a Ni foil / FAPbI3 photoanode.

[0192]

[0193] (10) Manufacturing of unassisted water splitting PEC panel reactor

[0194] The PEC panel reactor was designed using AUTOCAD's 3D MAX software and manufactured from transparent acrylic plastic. The performance evaluations of each individual photoanode and the water splitting reaction were performed in a two-compartment PEC panel reactor. Detailed schematics and photographs are shown in Figures 27 and 28.

[0195]

[0196] (11) Measurement of material properties

[0197] The morphology of FAPbI3 thin films and energy-dispersive X-ray spectroscopy (EDS) of the NiFeOOH / Ni foil surface were measured using a cold field-effect electron microscope (SU-8220, Hitachi High-Technologies). The optical properties of the FAPbI3PV cell and NiFeOOH / Ni / FAPbI3 were measured using a UV-Vis spectrophotometer (Shimadzu, UV-2600) and a UV-Vis-NIR spectrophotometer (Shimadzu, UV-3600) for the absorbance of the photoanode before and after the stability test. X-ray diffraction (XRD) measurements were performed using a high-resolution XRD instrument (D8 Discovery, Bruker). Electrochemical impedance spectroscopy (EIS) measurements were performed using a Metrohm Autolab (AUT302N) system. X-ray photoelectron spectroscopy (XPS) spectra were recorded using a high-transmission instrument (K-alpha, ThermoFisher Scientific) with a high-flux energy range of 200 eV–3 keV, and spectra were fitted using the Gaussian method in Origin software. ToF-SIMS depth profiling and 3D analysis were performed using a dual-beam (ToF-SIMS 5, IONTOF) instrument. Bi 3+ The pulsed primary ion beam is 250 × 250 μm 2 For the erosion of the substrate size, 30 keV was used as the applied potential and 1.2 pA as the current, which was used as the primary source for analysis. For the stability test, inductively coupled plasma-optical emission spectroscopy (ICP-OES, 700-ES Varian) was performed to measure the leaching of 'Ni', 'Fe', and 'Pb' in 1 M KOH electrolyte.

[0198]

[0199] (12) Photovoltaic power measurement

[0200] The performance of the FAPbI3PV cell was measured using a solar simulator (Newport, Oriel Sol3A class AAA) and a calibrated silicon reference cell certified by NREL, USA. The JV characteristics of the FAPbI3PV cell were 100 mW cm -2 The photocurrent density was measured using a Keithley source meter (Keithley 2400) by a solar simulator under simulated 1-sun conditions (AM 1.5G) with an irradiance of 10 mV. The step voltage was 10 mV and the delay time was 40 ms. The active area was covered by a metal mask (0.094 cm) placed in front of the PSC for accurate measurement of the photocurrent density. 2 The aperture size was controlled by the surface anti-reflection coating for measurement of high-efficiency devices.

[0201]

[0202] (13) Photoelectrochemical measurements

[0203] All PEC measurements were performed using a three-electrode or two-electrode setup in the water-splitting PEC reactor cell of the present invention. Acidic (0.5 M H2SO4, pH 0.3), basic (1 M KOH, pH 14), and neutral (0.5 M KPi at pH 7, 0.5 M Na2SO3 at pH 9) electrolytes were tested. The size of the NiFeOOH / Ni / FAPbI3 photoanode and FAPbI3PV cell was 0.25 cm 2 The same was maintained. The solar simulator (Oriel Sol3A, Newport, USA) simulated sunlight (AM 1.5G, 100 mW cm) under 1-sun conditions. -2) was used to generate the fluorescence spectra, and an electrochemical setup (Iviumstat interface, IVIUM Technologies, USA) was used for linear sweep voltammetry (JV) and chronoamperometry (Jt) measurements under 1-sun irradiance. The light intensity was 100 mW cm using a thermopile detector with a spectrum from 0.19 to 10.6 μm. -2 was measured (Newport, 818P-020-12). Photoelectrochemical impedance spectroscopy (PEIS) measurements were performed at potentials corresponding to the maximum %ABPE in the frequency range of 0.1 Hz–1000 kHz in a three-electrode setup (Iviumstat interface, IVIUM Technologies, USA). All electrochemical measurements were performed under the same conditions as described above, but without illumination.

Claims

1. First lower electrode, A first electron transport layer formed on the first lower electrode, A first perovskite light-absorbing layer formed on the first electron transport layer, A first hole transport layer formed on the first light absorbing layer, A first upper electrode formed on the first hole transport layer; A first Ni thin film layer formed on the first upper electrode, and An oxygen generating unit including an oxygen generating reaction catalyst layer formed on the first Ni thin film layer; and Second lower electrode, A second electron transport layer formed on the second lower electrode layer, A second perovskite light-absorbing layer formed on the second electron transport layer, A second hole transport layer formed on the second light absorbing layer, A second upper electrode formed on the second hole transport layer and A passivation portion including a second Ni thin film layer formed on the second upper electrode; Including, A perovskite photoanode, wherein the first lower electrode and the second upper electrode are electrically connected.

2. A perovskite photoanode according to claim 1, wherein the first electron transport layer and the second electron transport layer include at least one selected from the group consisting of TiO2, SnO2, and ZnO.

3. In claim 1, the first light-absorbing layer and the second light-absorbing layer comprise a compound represented by the following chemical formula 1, a perovskite photoanode: ABX3 [chemical formula 1] In the above formula, A is a methylammonium (MA) or formamidinium (FA) cation, B is Pb 2+ , Sn 2+ , Ge 2+ , Cu 2+ , Ni 2+ , Co 2+ and Fe 2+ At least one divalent metal cation selected from the group consisting of, X is a halogen anion.

4. In claim 1, the first hole transport layer and the second hole transport layer are 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly(3-hexylthiophene) (P3HT), poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]] (PCPDTBT), and A perovskite photoanode comprising at least one selected from the group consisting of 7-(9,9'-spirobi[fluoren]-2-yl)-N-(7-(9,9'-spirobi[fluoren]-2-yl)-9,9-dioctyl-9H-fluoren-2-yl)-N-(4-(9H-carbazol-9-yl)phenyl)-9,9-dioctyl-9H-fluoren-2-amine (CzPAF-SBF).

5. A perovskite photoanode according to claim 1, wherein the first upper electrode and the second upper electrode include at least one selected from the group consisting of gold (Au), silver (Ag), and aluminum (Al).

6. A perovskite photoanode according to claim 1, wherein the thickness of the first Ni thin film layer and the second Ni thin film layer is 0.003 to 100 μm.

7. A perovskite photoanode according to claim 1, wherein the oxygen evolution reaction catalyst layer comprises at least one selected from the group consisting of NiFeOOH, NiOOH, and FeOOH.

8. A perovskite photoanode according to claim 1, further comprising an Ag layer between the first upper electrode and the first Ni thin film layer and between the second upper electrode and the second Ni thin film layer.

9. A perovskite photoanode according to claim 8, wherein the Ag layer is a cured layer of an adhesive in which Ag-coated polymer particles are dispersed.

10. A perovskite photoanode according to claim 1; cathode; and Mercury electrolyte; A water decomposition module comprising:

11. A water splitting module comprising a plurality of photoanodes according to claim 10.

12. A water-splitting module according to claim 10, wherein the aqueous electrolyte is a basic electrolyte.

13. A water splitting module according to claim 10 or 11; and A solar cell electrically connected to the above water splitting module; A water decomposition system comprising:

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