Composite for photoactive material, photoelectrode for oxygen evolution reaction comprising same, and method for manufacturing same

Abstract

The present invention relates to a composite for a photoactive material having excellent performance, a photoelectrode for an oxygen evolution reaction comprising same, and a manufacturing method therefor. Through various embodiments of the present invention, it is possible to ultimately achieve green hydrogen production through high-performance photoelectrochemical water splitting.

Description

Composite for photoactive material, photoelectrode for oxygen evolution reaction including same, and method for manufacturing same

[0001] The present invention relates to a composite for a photoactive material, a photoelectrode for an oxygen generation reaction including the composite, and a method for manufacturing the composite.

[0002]

[0003] The energy crisis is one of the major problems facing the modern world, a problem that must be solved to meet the increasing energy demand caused by industrial growth and population growth.

[0004] Recently, extensive research has been conducted on the development of clean, renewable energy through photoelectrochemical (PEC) water splitting. Hydrogen fuel has the highest gravimetric energy density of all fuels, making it a clean energy source for transportation, manufacturing, and various other sectors.

[0005] However, although photoelectrode materials must exhibit solar-to-hydrogen (STH) conversion efficiencies of more than 10% for commercial feasibility, the STH conversion efficiencies do not reach the requirements for practical applications.

[0006] To date, various metal oxide semiconductor-based photoelectrodes have been used in the oxygen evolution reaction (OER) and have successfully achieved significant efficiencies in converting light energy into useful chemicals and electricity. However, the activation of single metal oxides is limited to the ultraviolet region of the solar spectrum, which substantially hinders their applicability to practical solar energy conversion mechanisms.

[0007]

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] 1. Chinese Patent Publication No. 117822013

[0011] 2. Chinese Patent Publication No. 117845264

[0012] 3. Korean Patent Publication No. 10-2023-0030188

[0013] [Non-patent literature]

[0014] 1. Applied Catalysis B: Environmental 243 (2019): 657-666

[0015] 2. Chemistry of Materials (2024), 36(1), 275-285

[0016]

[0017] The present invention solves the technical problems of the existing technology discussed above, provides a composite for a photoactive material having excellent performance, a photoelectrode for an oxygen generation reaction including the composite, and a method for manufacturing the composite, and ultimately aims to achieve green hydrogen production through photoelectrochemical water decomposition.

[0018]

[0019] One aspect of the present invention relates to a ceramic of the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0022] x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9,

[0023] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

[0024] Another aspect of the present invention relates to a complex comprising the following (a1) and the following (a2).

[0025] (a1) semiconductor oxide, and

[0026] (a2) Ceramic of the following chemical formula 1:

[0027] [Chemical Formula 1]

[0028] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0029] x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9,

[0030] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

[0031] Another aspect of the present invention relates to a photoactive material, such as a photoelectrode or photocatalyst, comprising a composite according to various embodiments of the present invention.

[0032] Another aspect of the present invention relates to a photoelectrochemical (PEC) cell comprising (i) a working electrode and (ii) a counter electrode, wherein the working electrode is a photoelectrode according to various embodiments of the present invention.

[0033] Another aspect of the present invention relates to a water splitting device or a hydrogen generating device comprising a photoelectrochemical cell according to various embodiments of the present invention.

[0034] Another aspect of the present invention relates to various multifunctional materials, such as electrochemical catalysts, sensors, and supercapacitors, comprising composites according to various embodiments of the present invention, or to various devices, such as electrolysis devices and energy storage devices, comprising the same.

[0035] Another aspect of the present invention relates to a method for manufacturing a photoelectrode comprising the following steps.

[0036] (A) A step of forming a coating solution layer by coating a mixed solution containing (a1) and (a2) on a substrate:

[0037] (a1) semiconductor oxide precursor, and

[0038] (a2) Ball milled powder of ceramic expressed by the above chemical formula 1,

[0039] (B) a step of forming a coating layer by heating the coating liquid layer, and

[0040] (C) A step of forming a photoelectrode layer by firing the above coating layer.

[0041]

[0042] According to various embodiments of the present invention, the technical problems of the existing technology discussed above are solved, and a composite for a photoactive material having excellent performance, a photoelectrode for an oxygen evolution reaction including the composite, and a method for manufacturing the composite are provided, which ultimately enable green hydrogen production through photoelectrochemical water decomposition.

[0043]

[0044] Figure 1 shows the XRD patterns for pure BVO and BVO-ceramic composites, shown in black and red, respectively.

[0045] Figure 2 shows the XPS spectra for pure BiVO4 (BVO) and BVO-ceramic composites. (a) Bi4f, (b) V2p, (c) O1s, (d) Pb4f, (e) Cu2p, (f) S2p, (g) P2p

[0046] Figure 3 shows scanning electron microscope (SEM) images. (a) and (b) SEM images of pure BVO thin films, (d) and (e) SEM images of BVO-ceramic composite thin films, (c) cross-sectional image of pure BVO, and (f) cross-sectional image of BVO-ceramic composite.

[0047] Figure 4 shows transmission electron microscope (TEM) images of the BVO-ceramic composite photoelectrode. (a) to (c) at various magnifications, (d) corresponding STEM images, and (e) to (k) elemental mapping images for Bi, V, O, Pb, Cu, P, and S.

[0048] Figure 5 shows the results of linear sweep voltammetry (LSV) analysis for pure BVO photoelectrodes (black) and BVO-ceramic composite photoelectrodes (blue). (a) LSV curves, (b) chopped curves, (c) Nyquist plots for pure BVO photoelectrodes and BVO-ceramic composite photoelectrodes, and (d) schematic diagram of the electron transport mechanism of the BVO-ceramic composite photoelectrode.

[0049]

[0050] Below, various aspects and various implementation examples of the present invention will be examined in more detail.

[0051] In this specification, expressions such as ‘includes’, ‘has’, ‘consists of’, and ‘consists of’ may include other parts, as long as ‘only’ is not used.

[0052] In addition, when a component is expressed as singular in this specification, it also includes plural components unless otherwise explicitly stated.

[0053] Additionally, the numerical values ​​or numerical ranges described herein are interpreted to include an error range even if there is no separate explicit description.

[0054] Additionally, the expression “X to Y” indicating a numerical range in this specification means “X or more and Y or less.”

[0055] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, detailed descriptions of well-known functions or components that may obscure the gist of the present invention will be omitted in the following description and the attached drawings. Additionally, throughout the specification, the term "including" a component does not exclude other components, unless specifically stated otherwise, but rather implies the inclusion of other components.

[0056] Unless specifically defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology, and shall not be construed in an idealized or overly formal sense unless explicitly defined herein.

[0057]

[0058] One aspect of the present invention relates to a ceramic of the following chemical formula 1.

[0059] [Chemical Formula 1]

[0060] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0061] x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9,

[0062] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10It is a mistake of 4.

[0063] The above ceramic can be used as a photoelectrode, particularly a photoelectrode for oxygen evolution reaction (OER), in accordance with various aspects and various embodiments of the present invention; a photoelectrochemical cell, particularly a photoelectrochemical cell for water splitting or hydrogen generation; and various other multifunctional materials.

[0064] If some of the components constituting the above ceramic are missing or outside the above composition range, it is not preferable in that the effects according to various aspects and various embodiments of the present invention cannot be sufficiently expressed.

[0065] In particular, if some of the components constituting the above ceramic are missing or outside the above composition range, unlike the ceramic of the above composition according to the present invention, it is not effective in charge carrier separation, and thus the synergistic effect between BVO and the ceramic may not be observed.

[0066] Another aspect of the present invention relates to a complex comprising the following (a1) and the following (a2).

[0067] (a1) semiconductor oxide, and

[0068] (a2) Ceramic of the following chemical formula 1:

[0069] [Chemical Formula 1]

[0070] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0071] x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9,

[0072] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10It is a mistake of 4.

[0073] At this time, the semiconductor oxide may be selected from BiVO4, Fe2O3, FeVO4, and a combination of two or more thereof, and is preferably BiVO4.

[0074] In various aspects of the present invention, according to one embodiment, in the chemical formula 1, x is 2.1 to 9.9. When the amount of Cu doping increases, the band energy of the ceramic of chemical formula 1 changes, so that the conductivity can be greatly improved, which is preferable. However, when the amount exceeds the upper and lower limits, the effect of improving the conductivity or the photoelectrochemical performance of the composite photoelectrode including the same is insignificant, which is not preferable.

[0075] According to another embodiment, the composite includes the semiconductor oxide and the ceramic of the chemical formula 1 in a ratio of 0.04 to 400 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide. If it is less than the lower limit or exceeds the upper limit of the above range, the electrode including the semiconductor oxide-ceramic composite may not have a significant effect on improving hole mobility and charge carrier separation efficiency at the electrode-electrolyte interface compared to a pure BVO electrode, which is not preferable.

[0076] [Chemical Formula 1]

[0077] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0078] x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9,

[0079] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

[0080] According to another embodiment, the composite includes the semiconductor oxide and the ceramic of the chemical formula 1 in a ratio of 0.25 to 0.55 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide. If the ratio is outside the above range, the electrode including the semiconductor oxide (BVO)-ceramic composite may not have a significant effect of improving charge separation efficiency and electron mobility compared to a pure BVO electrode, which is not preferable.

[0081] According to another embodiment, the complex exhibits effective peaks at 2θ of 18° to 20°, 28° to 30°, 29.5° to 31.5°, 33.3° to 34.1°, 34.5° to 34.8°, 39.5° to 40.15°, 46.1° to 46.9°, and 51.1° to 51.8°, and does not exhibit effective peaks at 2θ of 43.0° to 43.8°.

[0082] Pure BiVO4 has a monoclinic Scheelite structure and shows the standard diffraction pattern of JCPDS #140688. However, the composite according to one embodiment of the present invention shows effective peaks for monoclinic (200), (022), (112) planes at the same 2θ as pure BiVO4, and effective peaks for monoclinic (110), (121), (040), (002) planes at a slightly lower 2θ than pure BiVO4, and, unlike pure BiVO4, does not show an effective peak for tetragonal (013) plane.

[0083] According to a particularly preferred embodiment, the composite of the present invention preferably shows effective peaks at 2θ of 18° to 20°, 28° to 30°, 29.5° to 31.5°, 33.3° to 34.1°, 34.5° to 34.8°, 39.5° to 40.15°, 46.1° to 46.9°, and 51.1° to 51.8° as a result of X-ray diffraction (XRD) analysis, and does not show effective peaks at 2θ of 43.0° to 43.8°, and when it has a crystal structure showing all of the characteristics of these XRD patterns, when it forms a composite with a semiconductor oxide (BVO) and is utilized as an electrode, compared to a case where none of the characteristics of the above XRD patterns are shown, the photocurrent density and the charge transfer resistance at the electrode-electrolyte interface are improved compared to a pure BVO electrode, and the hole mobility at the electrode-electrolyte interface is improved. It is desirable because the effect of improving the charge carrier separation efficiency can be significantly increased.

[0084] According to another embodiment of the present invention, the complex is characterized by X-ray photoelectron spectroscopy (XPS) analysis results showing that Bi(4f 5 / 2 ) binding energy, Bi(4f 5 / 2 ) binding energy, V(2p 3 / 2 ) binding energy, V(2p 1 / 2 ) binding energy, O(1s) binding energy is higher than that of pure BiVO4.

[0085] According to another preferred embodiment, the composite has an average crystal size of 40-50 nm as determined by X-ray diffraction analysis, an average particle diameter of 500-1,500 nm as determined by dynamic light scattering (DLS) analysis, and a full-width at half maximum (FWHM) of 1,000 nm or less. This is related to the ball milling conditions described below. When the ball milling conditions are particularly 400-700 rpm and 3-36 hours, not only does the average crystal size decrease to 40-50 nm, but the average particle diameter also becomes uniform to 500-1,500 nm and the full-width at half maximum of the particle diameter becomes 1,000 nm or less, which can be advantageous in further improving the photoelectrochemical performance when utilized in a photoelectrode.

[0086] According to a more preferred embodiment, the composite has an average crystal size of 40-50 nm as determined by X-ray diffraction analysis, and an average particle diameter of 500-1,500 nm and a full width at half maximum of 500 nm or less as determined by dynamic light scattering (DLS) analysis. This is also related to the ball milling conditions described below. When the ball milling conditions are particularly 450-550 rpm and 5-7 hours, the average crystal size also decreases to 40-50 nm, the average particle diameter becomes uniform to 500-1,500 nm, and the full width at half maximum of the particle diameter also becomes uniform to 500 nm or less, which may be advantageous in further improving the photoelectrochemical performance when utilized in a photoelectrode.

[0087] According to a further preferred embodiment, the complex comprises the semiconductor oxide and the ceramic of the chemical formula 1 in a ratio of 0.25 to 0.55 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide, and the complex has an average crystal size of 40-50 nm as a result of X-ray diffraction analysis, and an average particle diameter of 500-1,500 nm and a full width at half maximum of 500 nm or less as a result of dynamic light scattering (DLS) analysis.

[0088] As described above, (i) when the mixing molar ratio (loading amount) of the semiconductor oxide and the ceramic of the chemical formula 1 is controlled so that the ratio of the ceramic of the chemical formula 1 is 0.25 to 0.55 mmol based on 1 mol of the semiconductor oxide, and (ii) the ball milling conditions of the composite are controlled together so that (ii-1) the average crystal size is 40-50 nm, (ii-2) the average particle diameter is 500-1,500 nm, and (iii-3) the particle diameter has a full width at half maximum of 500 nm or less, unlike a case where even one of the above conditions is not satisfied, a photoelectrode including such a composite exhibits a significantly increased photocurrent density as a result of linear sweep voltammetry (LSV) analysis, and a significantly reduced charge transfer resistance at the electrode-electrolyte interface as a result of electrochemical impedance spectroscopy (EIS) analysis, which may be more preferable.

[0089] Another aspect of the present invention relates to a photoactive material comprising a composite according to various embodiments of the present invention.

[0090] Non-limiting examples of photoactive materials according to the present invention include, but are not limited to, photoelectrodes or photocatalysts. The photoelectrode may be a thin film layer formed on at least a portion of the surface of a substrate, including the composite according to the present invention, and the photocatalyst may be a composite according to the present invention supported on a carrier.

[0091] In this respect, the present invention may relate to a photoelectrode comprising (b) a substrate, and (a) a photoelectrode layer formed on at least a portion of the surface of the substrate, wherein the photoelectrode layer comprises a composite according to various embodiments of the present invention.

[0092] At this time, the thickness of the photoelectrode layer is 1.2-1.3 μm, which is preferable in that it can organically combine with the configuration according to various embodiments of the present invention to synergistically improve the performance of the photoelectrode.

[0093] In one embodiment, the photoelectrode is for oxygen evolution reaction (OER).

[0094] Another aspect of the present invention relates to a photoelectrochemical (PEC) cell comprising (i) a working electrode and (ii) a counter electrode, wherein the working electrode is a photoelectrode according to various embodiments of the present invention.

[0095] Another aspect of the present invention relates to a water splitting device comprising a photoelectrochemical cell according to various embodiments of the present invention.

[0096] Another aspect of the present invention relates to a hydrogen generation device comprising a photoelectrochemical cell according to various embodiments of the present invention, wherein the composite according to the present invention is applied to a working electrode and hydrogen is generated at a counter electrode.

[0097] In addition, another aspect of the present invention may be a multifunctional material comprising a composite according to various embodiments of the present invention. Non-limiting examples of multifunctional materials in the present invention include, but are not limited to, photoelectrodes, photocatalysts, electrochemical catalysts, sensors, supercapacitors, and the like.

[0098] Another aspect of the present invention relates to a device comprising a multifunctional material according to various embodiments of the present invention, which can be utilized as a gas generator, a photoelectrochemical water splitting device, an electrochemical water electrolysis device, an electricity generating device such as a fuel cell, an energy storage device including a battery or a supercapacitor, or a communication or transportation device including one or more of these.

[0099] In particular, when used as a gas generator, the type of gas generated may vary depending on the semiconductor oxide used. In the case of BiVO4 or FeVO4, it can be used as an oxygen generator utilizing an oxygen evolution reaction (OER), and in the case of Fe2O3, it can be used as a hydrogen generator utilizing a hydrogen evolution reaction (HER).

[0100] However, the gas generated is not limited thereto. For example, in the case of BiVO4 or FeVO4, oxygen can be generated by using this as a working electrode, and hydrogen can also be generated simultaneously by using Pt or the like as a counter electrode. Therefore, the gas generating device of the present invention should be broadly interpreted as a gas to be generated in that it can be used as a gas generating device that generates oxygen and hydrogen simultaneously.

[0101] It is clear that not only a composite including a ceramic and a semiconductor oxide in which the Cu doping amount in Chemical Formula 1 is controlled to, for example, 2.1 to 9.9, but also a composite including a known ceramic and a semiconductor oxide in which the Cu doping amount in Chemical Formula 1 is lower than this is included in the scope of the present invention, but the composite including a ceramic and a semiconductor oxide of Chemical Formula 1 with an increased Cu doping amount of the present invention is more preferable because the catalytic activity is greatly increased compared to a composite including a ceramic and a semiconductor oxide of Chemical Formula 1 manufactured by a conventional method when applied as a photoactive material for an oxygen evolution reaction.

[0102] According to one embodiment, in the above chemical formula 1, x is 2.1 to 9.9. When the amount of Cu doping increases, the band energy of the ceramic of chemical formula 1 changes, so that the conductivity can be significantly improved, which is preferable. However, when the amount exceeds the upper and lower limits, the effect of improving the conductivity or the photoelectrochemical performance of the composite photoelectrode including the same is insignificant, which is not preferable.

[0103] Another aspect of the present invention relates to a method for manufacturing a photoelectrode comprising the following steps.

[0104] (A) A step of forming a coating solution layer by coating a mixed solution containing (a1) and (a2) on a substrate:

[0105] (a1) semiconductor oxide precursor solution, and

[0106] (a2) Ball milled solution obtained by ball milling a dispersion of a ceramic represented by the following chemical formula 1:

[0107] [Chemical Formula 1]

[0108] Pb 10-x Cu x [(PO4) 6-y (SO4) y ]O z S z'

[0109] x is a real number between 0.9 and 9.9, and y is 10 -10It is a real number of 5.9,

[0110] z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

[0111] (B) a step of forming a coating layer by heating the coating liquid layer, and

[0112] (C) A step of forming a photoelectrode layer by firing the above coating layer.

[0113] According to one embodiment, the semiconductor oxide is BiVO4.

[0114] In another embodiment, x is 2.1 to 9.9.

[0115] According to another embodiment, the mixed solution includes the semiconductor oxide precursor and the ceramic of the chemical formula 1 in a molar ratio of 1:0.008 to 0.8. If it is less than the lower limit or more than the upper limit of the above range, the electrode including the semiconductor oxide (BVO)-ceramic composite may not have a significant effect on improving hole mobility and charge carrier separation efficiency at the electrode-electrolyte interface compared to a pure BVO electrode, which is not preferable.

[0116] According to another embodiment, the mixed solution includes the semiconductor oxide precursor and the ceramic of the chemical formula 1 in a ratio of 0.04 to 400 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide precursor. If the ratio is outside the above range, the electrode including the semiconductor oxide (BVO)-ceramic composite may not have a significant effect of improving charge separation efficiency and electron mobility compared to a pure BVO electrode, which is not preferable.

[0117] According to another embodiment, the ball milling is performed at 400 to 700 rpm for 3 to 36 hours. Such ball milling conditions are related to the above-mentioned average crystal size, average particle diameter, and full width at half maximum, and it is preferable that the composite has an average crystal size of 40 to 50 nm as a result of X-ray diffraction analysis, and an average particle diameter of 500 to 1,500 nm and a full width at half maximum of 1,000 nm or less as a result of dynamic light scattering (DLS) analysis. When the ball milling conditions are particularly 400 to 700 rpm and 3 to 36 hours, not only does the crystal size decrease to 40 to 50 nm, but the average particle diameter also becomes 500 to 1,500 nm, and the full width at half maximum of the particle diameter also becomes uniform at 1,000 nm or less, which can be advantageous in further improving the photoelectrochemical performance when utilized in a photoelectrode.

[0118] In another embodiment, the composite comprises (i) the semiconductor oxide and the ceramic of the formula 1 in a ratio of 0.25 to 0.55 mmol of the ceramic of the formula 1 based on 1 mol of the semiconductor oxide precursor, (ii) ball milling is performed at 450 to 550 rpm for 5 to 7 hours, and the composite has (ii-1) an average crystal size of 40 to 50 nm as a result of X-ray diffraction analysis, and (ii-2) an average particle size of 500 to 1,500 nm as a result of dynamic light scattering analysis, and (ii-3) a full width at half maximum of 500 nm or less as a result of particle size. When the loading amount of the ceramic of the formula 1 and the ball milling conditions are adjusted together as above, unlike a case where even one of the above conditions is not satisfied, the photocurrent density can be greatly increased and the charge transfer resistance at the interface between the electrode and the electrolyte can be greatly reduced, which can be very advantageous when utilized as a photoactive material.

[0119] According to a preferred embodiment, the mixed solution is a binder-free solution. Another significance of the present invention lies in the fact that excellent effects can be achieved without the use of a binder, which is essential in existing methods.

[0120] Non-limiting examples of methods for performing the above coating include, but are not limited to, spin coating, doctor blade coating, inkjet printing, etc. However, according to a more preferred embodiment, the coating is preferably performed using an electrostatic spray deposition (ESD) method in terms of thickness uniformity, film density, and surface smoothness.

[0121] According to another embodiment, the heating is performed at 150 to 500°C for 40 minutes to 5 hours, and the calcination is performed at 400 to 700°C for 40 minutes to 5 hours.

[0122] It is preferable to perform a heating step after coating in that it can remove residual solvent traces and increase the adhesive strength of the ceramic of chemical formula 1, and it is more preferable to perform it at a temperature of 150 to 350°C for 40 minutes to 5 hours.

[0123] It is also desirable to additionally perform a calcination step after heating, and more preferably to perform it at a temperature of 400 to 700°C for 40 minutes to 5 hours.

[0124] Hereinafter, the present invention will be described in more detail through examples and the like. However, the scope and content of the present invention should not be construed as being limited or reduced by the examples and the like. Furthermore, based on the disclosure of the present invention, including the following examples, it is clear that those skilled in the art can easily implement the present invention, even though specific experimental results are not presented. It is also natural that such variations and modifications fall within the scope of the appended claims.

[0125] In addition, the experimental results presented below only describe representative experimental results of the above examples and comparative examples, and the effects of each of the various embodiments of the present invention that are not explicitly presented below will be specifically described in the relevant section.

[0126] Example

[0127] Chemical substances

[0128] Bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), vanadyl acetylacetone (C 10 H 14 O5V) was used as a precursor, and acetic acid, dimethyl sulfoxide (C2H6OS), acetone, and methanol were used as solvents. All chemicals were of AR grade and used without further purification.

[0129] Manufacturing Example 1: Preparation of BiVO4 (BVO) precursor solution

[0130] A Bi solution was prepared by dissolving 1.21 g of bismuth nitrate pentahydrate in 10 mL of acetic acid, and a V solution was prepared by dissolving 0.99 g of vanadyl acetylacetone in 110 mL of dimethyl sulfoxide (DMSO). The two solutions were slowly mixed while continuously stirred to prepare a BVO precursor solution.

[0131] Manufacturing Example 2: Ceramic Manufacturing

[0132] Powders of PbO, PbSO4, Cu, and P were prepared in the molar ratio of the molecules to be synthesized and mixed uniformly. The mixture was placed in a reaction tube (quartz tube or copper tube), vacuumed, sealed, and heated at 770°C for 12 hours to perform the reaction. After the reaction was completed, the granules produced in the reaction tube were powdered, reduced to a near-vacuum state, and heated at 550°C for 5 hours for the second time. Through this process, solid sulfur was sublimated, and the sublimated sulfur was removed in the molar ratio through the evacuation process to manufacture a ceramic.

[0133] For example, when synthesizing a ceramic with a doping amount of Cu adjusted to 2 moles, the molar ratio of the raw materials is mixed as PbO: PbSO4: Cu: P = 2:6:2:6, and as another example, the composition is Pb 7.38 Cu 2.62 (PO4) 5.46 (SO4) 0.54 O 0.66 S 0.84 When synthesizing phosphorus ceramics, the molar ratio of raw materials is mixed as PbO: PbSO4: Cu: P = 1.38:6:2.62:6.

[0134] Manufacturing Example 3: Manufacturing of ball-milled ceramic powder and ball-milled solution

[0135] Pb 7.38 Cu 2.62 (PO4) 5.46 (SO4) 0.54 O 0.66 S 0.84 A ball milled powder of a ceramic of chemical formula 1 was obtained by ball milling a ceramic (structure confirmed through XPS and XRD, molecular weight 2,303) at 500 rpm for 6 hours, and this was dispersed in ethanol to prepare a ball milled solution of a ceramic of chemical formula 1.

[0136] Comparative Manufacturing Example 1: Ceramic Manufacturing

[0137] Pb9Cu(PO4)6O (CAS No. 2972464-09-6) was prepared according to a known method, such as Chemistry of Materials (2024), 36(1), 275-285.

[0138] Comparative Manufacturing Example 2: Ceramic Manufacturing

[0139] Pb9Cu(PO4) according to the method disclosed in Korean Patent Publication No. 10-2023-0030188 (Patent Application No. 10-2021-0112104) 5.5 (SO4) 0.5 S 3.5 was manufactured.

[0140]

[0141] Comparative Example 1: Preparation of pristine BiVO4 (BVO) electrode

[0142] The BVO precursor solution prepared in Manufacturing Example 1 was injected into a syringe and then coated on a fluorine-doped tin oxide (FTO) substrate using electrostatic spray deposition (ESD) under the conditions shown in Table 1 below. The substrate was then placed on a hot plate in an open atmosphere and maintained at 300°C. The light yellow film thus produced was calcined at 500°C for 1 hour for further characterization.

[0143] Spray coating amount (mL) 1-5 Flow rate (μL) 20-80 Deposition time (min) 15-50 Nozzle-to-substrate distance (cm) 5-25 Nozzle size (gauge) 21-29 Deposition temperature (℃) 80-140

[0144] Example: Fabrication of BVO-ceramic composite electrode

[0145] The BVO precursor solution manufactured in Manufacturing Example 1 and the ball milled solution of the ceramic manufactured in Manufacturing Example 3 were mixed and injected into a syringe, and then coated on an FTO substrate using the electrostatic spray deposition (ESD) method under the same conditions as in Comparative Example 1.

[0146] The mixing ratio of the BVO precursor solution and the ball milled solution of the ceramic was changed for each solution so that 0.2 mmol, 0.4 mmol, 0.6 mmol, and 0.8 mmol of the ceramic of chemical formula 1 were included based on 1 mol of the BVO precursor.

[0147] Then, the substrate was placed on a hot plate in an open atmosphere and maintained at 300°C. The light yellow film thus produced was fired at 500°C for 1 hour for further characterization.

[0148] Comparative Examples 2 and 3: Preparation of BVO-ceramic composite electrodes

[0149] A BVO-ceramic composite electrode was manufactured in the same manner as in the examples, except that the ceramics manufactured in Comparative Manufacturing Examples 1 and 2 were used instead of the ceramics manufactured in Manufacturing Example 2 (Comparative Examples 2 and 3, respectively).

[0150]

[0151] Test Example 1: X-ray Diffraction Analysis

[0152] XRD analysis was performed on the pure BVO manufactured in Comparative Example 1 and the BVO-ceramic composite manufactured in the examples, and the results are presented in Fig. 1.

[0153] As a result, pure BVO shows peaks in the region where both monoclinic and tetragonal structures appear (2θ of 19.0°, 28.98°, 30.50°, 33.5°, 34.67°, 35.25°, 40.07°, 43.5°, 46.5, 51.5, etc.), which correspond to mono(110) or tet(101), mono(130), mono(040) or tet(121), mono(200), tet(200), mono(220) or tet(022), mono(150), tet(013), tet(132), and mono(022) or tet(213), respectively (JCPDS #140688).

[0154] The BVO-ceramic composite also showed a similar XRD pattern in the monoclinic (110), (200), (220), (022), and (112) crystal planes, but the peaks corresponding to the other crystal planes were confirmed to have shifted to lower angles (see Insert A), which means that the distance between the planes was relatively expanded.

[0155] Additionally, it was confirmed that the BVO-ceramic composite did not show a peak corresponding to the tetragonal (013) crystal plane that pure BVO shows (see inset B), which can be seen that some of the tetragonal structures underwent a structural change to a relatively more disordered monoclinic system.

[0156] Test Example 2: X-ray Photoelectron Spectroscopy (XPS) Analysis

[0157] XPS analysis was performed on the pure BVO manufactured in Comparative Example 1 and the BVO-ceramic composite manufactured in the examples, and the results are presented in Fig. 2.

[0158] The binding energy of pure BVO photoelectrode is 163.89 eV (Bi4f 5 / 2 ) and 158.64 eV (Bi4f7 / 2 ) is separated into two peaks (Fig. 2a). However, in the case of the BVO-ceramic composite photoelectrode, the binding energy was slightly higher, appearing at 164.28 eV and 158.98 eV, respectively.

[0159] In addition, both photoelectrodes showed a small change in the V2p binding energy (Fig. 2b). For the BVO photoelectrode, it was 523.58 eV (V2p 3 / 2 ) and 516.55 eV (V2p 1 / 2 ) were found to slightly shift to 524.24 eV and 516.95 eV for the BVO-ceramic composite, respectively. This shift was attributed to the V 5+ This may be due to changes in electronegativity nearby.

[0160] The O1s spectrum in Fig. 2c shows that the binding energy shifted from 531.35 eV for pure BVO to 532.21 eV and from 529.50 eV to 530.02 eV for the BVO-ceramic composite. This suggests that the bond length was lengthened due to a slight increase in the interatomic distance, in light of the XRD analysis results (a trend of volume expansion and a change to a disordered monoclinic structure).

[0161] The binding energy of Pb4f is 138.26 eV (Pb4f 7 / 2 ) and 143.17 eV (Pb4f 5 / 2 ) is separated into two peaks (Fig. 2d). Also, in the case of Cu2p, the two peaks of the Cu2p core level are 927.17 eV (Cu2p 3 / 2 ) and 952.07.33 eV (Cu2p 1 / 2 ) is located (Fig. 2e).

[0162] Figure 2f shows the S2p spectrum of the BVO-ceramic composite photoelectrode, where the satellite peak observed at 169.19 eV indicates the presence of sulfur in the composite. Additionally, the satellite peak observed at approximately 130 eV indicates the presence of phosphorus in the composite (Figure 2g).

[0163] Test Example 3: Scanning Electron Microscope (SEM) Analysis

[0164] SEM analysis was performed on the pure BVO manufactured in Comparative Example 1 and the BVO-ceramic composite manufactured in the examples, and the results are presented in Fig. 3.

[0165] As shown in Figures 3a and 3b, SEM images of pure BVO show a spherical morphology composed of round particles with a size of 50 to 70 nm uniformly distributed on the FTO substrate. Figure 3b clearly shows spherical porous particles with a size of approximately 50 nm on the FTO substrate.

[0166] Figures 3d and 3e are images at different magnifications of the BVO-ceramic composite sample, showing agglomerated and interconnected spherical BVO particles homogeneously anchored on the BVO-ceramic surface. The smooth surface of the agglomerated particles was observed, and the particle size was approximately 40–50 nm. The BVO particles are visible in the images due to the very small amount of ceramic, and the addition of ceramic may cause agglomeration of the BVO particles. The introduction of ceramic into the BVO particles changes the behavior of the composite in a multi-channel environment, promoting efficient charge interactions, effectively separating photogenerated carriers, and consequently enhancing the photoelectrochemical performance.

[0167] Cross-sectional views of the morphology of pure BVO and BVO-ceramic composite photoelectrodes are presented in Figures 3c and 3f, respectively. Figure 3c shows that the surface of the FTO substrate was uniformly coated with a BVO film with a thickness of 0.8 to 0.9 μm. Figure 3f shows a cross-sectional image of a BVO-ceramic composite with a thickness ranging from 1.2 to 1.3 μm, indicating that the addition of ceramic to BVO resulted in an increase in thickness.

[0168] Test Example 4: TEM Analysis and STEM / EDS Analysis

[0169] The morphology and crystal structure were also analyzed using a transmission electron microscope (TEM), and the results are presented in Figure 4. Figures 4a to 4k show TEM images of the BVO-ceramic composite at various magnifications. Figure 4a clearly shows a porous spherical morphology with a diameter of approximately 50 to 60 nm, which is in good agreement with the SEM results. The observed porous surface structure can enhance the photoelectrochemical reaction by providing more accessible surface sites. This porous structure is particularly effective in increasing the area of ​​the electrode-electrolyte interface, promoting the transport of photogenerated electron-hole pairs and reducing the charge recombination rate in the photoelectrochemical water splitting reaction. Figure 4c shows a high-resolution image of the BVO-ceramic composite, showing lattice fringes consistent with the single-crystal structure of monoclinic BVO, which further supports the XRD data.

[0170] Additionally, elemental mapping was analyzed using STEM / EDS (Scanning Transmission Electron Microscopy / Energy Dispersive X-ray Spectroscopy) (Figs. 4d to 4k), showing that bismuth, vanadium, oxygen, lead, copper, phosphorus, and sulfur were uniformly distributed across the surface. The unique morphology of the as-prepared sample suggests its potential as a highly effective material for photoelectrochemical water splitting.

[0171] Test Example 5: Linear Scanning Voltametry (LSV) and Electrochemical Impedance Spectroscopy (EIS) Analysis

[0172] The photoelectrochemical (PEC) performance of the pure BVO photoelectrode prepared in Comparative Example 1 and the BVO-ceramic composite photoelectrode prepared in the examples was evaluated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS).

[0173] The photoelectrochemical (PEC) properties of the photoanodes were measured using a three-electrode optical cell configuration with a multichannel potentiostat. In this setup, the photoanodes served as the working electrode, a platinum electrode as the counter electrode, a saturated Ag / AgCl electrode as the reference electrode, and 0.5 M Na2SO4 as the electrolyte for water oxidation. Photoelectrochemical measurements of the individual electrodes were performed using a high-purity quartz reactor. A 300 W Xe lamp was used as the light source and was calibrated with a Sun Checker. Cutoff curves and photocurrent densities were obtained by linear sweep voltammetry (LSV). Electrochemical impedance spectroscopy (EIS) was performed under dark and light conditions.

[0174] First, the pure BVO photoelectrode manufactured in Comparative Example 1 and the BVO-ceramic composite photoelectrode manufactured in the examples were assembled, respectively. The prepared photoelectrodes were analyzed by linear scanning voltammetry (LSV) under dark conditions, light irradiation conditions, and light blinking (on-off) conditions.

[0175] The photocurrent density (0.35 mA / cm²) of the BVO-ceramic composite electrode was confirmed to be approximately three times higher than that of the reference BVO electrode (0.12 mA / cm²) in a 0.5 M Na2SO4 electrolyte. This suggests that the introduction of ceramics can enhance electrical conductivity and charge carrier transport, thereby promoting photocurrent.

[0176] Next, electrochemical impedance spectroscopy (EIS) was performed to investigate the charge transfer rate. Nyquist plots of pure BVO and BVO-ceramic composites were generated in 0.5 M Na2SO4 electrolyte. As illustrated in Fig. 5c, the semicircle diameter in the high-frequency region generally corresponds to the charge transfer resistance (R ct ) indicates that pure BVO has high R ct It exhibits low charge carrier separation efficiency due to this, which means that the catalytic activity for water oxidation is reduced due to insufficient hole transfer at the electrode / electrolyte interface.

[0177] On the other hand, the introduction of ceramics significantly reduced the charge transfer resistance compared to pure BVO, which means that the introduction of ceramics reduced the resistance by increasing the charge carrier density and electrical conductivity.

[0178] Finally, it was confirmed that the synergistic effect of BVO and ceramics is very effective in excellent charge carrier separation and ultimately can improve the overall water splitting performance.

[0179] In addition, although drawings and the like were not provided, it was confirmed that the BVO-ceramic composite electrodes manufactured in Comparative Examples 2 and 3 above not only had significantly lower overall catalytic activity, including final water splitting performance, compared to the BVO-ceramic composite electrode of the example, but also were not effective in charge carrier separation, unlike the BVO-ceramic composite electrode of the example, so that no synergistic effect between BVO and ceramic was observed.

Claims

1. Ceramic of the following chemical formula 1: [Chemical Formula 1] Pb 10-x With x [(PO4) 6-y (SO4) y ]A z S z' x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9, z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

2. A complex comprising (a1) and (a2): (a1) semiconductor oxide, and (a2) Ceramic of the following chemical formula 1: [Chemical Formula 1] Pb 10-x With x [(PO4) 6-y (SO4) y ]A z S z' x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9, z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4.

3. In the second paragraph, the semiconductor oxide is a composite selected from BiVO4, Fe2O3, FeVO4, and a combination of two or more thereof.

4. In the second paragraph, the semiconductor oxide is a complex of BiVO4.

5. A complex according to claim 2, wherein x is 2.1 to 9.

9.

6. In the second paragraph, the complex is a complex comprising the semiconductor oxide and the ceramic of the chemical formula 1 in a ratio of 0.04 to 400 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide.

7. In the second paragraph, the complex is a complex comprising the semiconductor oxide and the ceramic of the chemical formula 1 in a molar ratio of 1:0.5 to 0.11, with 0.25 to 0.55 mmol of the ceramic of the chemical formula 1 based on 1 mol of the semiconductor oxide.

8. In the second paragraph, the base complex is as a result of X-ray diffraction (XRD) analysis, 2θ shows effective peaks at 18° to 20°, 28° to 30°, 29.5° to 31.5°, 33.3° to 34.1°, 34.5° to 34.8°, 39.5° to 40.15°, 46.1° to 46.9°, and 51.1° to 51.8°, A complex that does not exhibit a significant peak at 2θ of 43.0° to 43.8°.

9. In paragraph 2, the results of X-ray photoelectron spectroscopy (XPS) analysis, The above complex is Bi(4f 5 / 2 ) binding energy, Bi(4f 5 / 2 ) binding energy, V(2p 3 / 2 ) binding energy, V(2p 1 / 2 ) binding energy, and the O(1s) binding energy is higher than that of pure BiVO4.

10. A photoactive material comprising a complex according to any one of claims 2 to 9. 11.(b) a substrate, and (a) a photoelectrode including a photoelectrode layer formed on at least a portion of the substrate surface, A photoelectrode comprising a composite according to any one of claims 2 to 9, wherein the photoelectrode layer is a photoelectrode.

12. In the 11th paragraph, the photoelectrode layer has a thickness of 1.2 to 1.3 μm.

13. In the 11th paragraph, the photoelectrode is a photoelectrode for oxygen evolution reaction (OER).

14. A photoelectrochemical (PEC) cell comprising (i) a working electrode, (ii) a counter electrode, and (iii) a reference electrode, A photoelectrochemical cell wherein the working electrode is a photoelectrode according to claim 11.

15. A water splitting device comprising a photoelectrochemical cell according to Article 14.

16. A hydrogen generating device comprising a photoelectrochemical cell according to Article 14.

17. A multifunctional material comprising a composite according to any one of claims 2 to 9.

18. A device comprising a multifunctional material according to Article 17.

19. A method for manufacturing a photoelectrode comprising the following steps: (A) A step of forming a coating solution layer by coating a mixed solution containing (a1) and (a2) on a substrate: (a1) semiconductor oxide precursor, and (a2) Ball milled powder of a ceramic represented by the following chemical formula 1: [Chemical Formula 1] Pb 10-x With x [(PO4) 6-y (SO4) y ]A z S z' x is a real number between 0.9 and 9.9, and y is 10 -10 It is a real number of 5.9, z and z' are 10 each -10 is a real number of 4, and z+z' is 10 -10 It is a mistake of 4. (B) a step of forming a coating layer by heating the coating liquid layer, and (C) A step of forming a photoelectrode layer by firing the above coating layer.

20. A method for manufacturing a photoelectrode, wherein the semiconductor oxide is BiVO4.

21. A method for manufacturing a photoelectrode in claim 19, wherein x is 2.1 to 9.

9.

22. A method for manufacturing a photoelectrode in claim 19, wherein the mixed solution contains the semiconductor oxide precursor and the ceramic of the chemical formula 1 in a molar ratio of 1:0.008 to 0.

8.

23. A method for manufacturing a photoelectrode in claim 19, wherein the mixed solution contains the semiconductor oxide precursor and the ceramic of the chemical formula 1 in a molar ratio of 1:0.4 to 0.

11.

24. A method for manufacturing a photoelectrode in claim 19, wherein the ball milled powder of the ceramic is obtained by performing ball milling at 400-700 rpm for 3-36 hours.

25. A method for manufacturing a photoelectrode according to claim 19, wherein the ball milled powder of the ceramic is obtained by performing ball milling at 450 to 550 rpm for 5 to 7 hours.

26. A method for manufacturing a photoelectrode in claim 19, wherein the ball milled powder of the ceramic has (i) an average crystal size of 40 to 50 nm as a result of X-ray diffraction analysis, and (ii) an average particle diameter of 500 to 1,500 nm and a full width at half maximum of 500 nm or less as a result of dynamic light scattering (DLS) analysis.

27. In paragraph 19, the mixed solution contains the semiconductor oxide precursor and the ceramic of the chemical formula 1 in a molar ratio of 1:0.05 to 0.11, A method for manufacturing a photoelectrode, wherein the above complex has an average crystal size of 40 to 50 nm as a result of X-ray diffraction analysis and an average particle diameter of 500 to 1,500 nm and a full width at half maximum of 500 nm or less as a result of dynamic light scattering (DLS) analysis.

28. A method for manufacturing a photoelectrode, wherein the mixed solution in claim 19 is a binder-free solution.

29. A method for manufacturing a photoelectrode in claim 19, wherein the coating is performed by electrostatic spray deposition.

30. In the 19th paragraph, the heating is performed at 150 to 500°C for 40 minutes to 5 hours, A method for manufacturing a photoelectrode, wherein the above-mentioned firing is performed at 400 to 700°C for 40 minutes to 5 hours.

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