Single crystalline ta3n5 nanoparticles modified with a mox cocatalyst, a catalyst, methods for water splitting using the catalyst, and methods to make same

Abstract

This paper discloses tantalum nitride, and more particularly a novel Ta3N5 nanoparticle, such as single-crystal Ta3N5 nanoparticles. This paper further discloses nanoparticles used in conjunction with co-catalysts. The invention also relates to Ta3N5 nanoparticles modified with metal oxides (such as CoOx co-catalysts, where Ox represents an oxide that is part of cobalt oxide). This paper discloses a catalyst, such as for the oxidation of water to produce O2. These nanoparticles can be further modified to include a water reduction catalyst. This paper further discloses a water splitting catalyst. This paper also discloses methods for manufacturing these nanoparticles and the catalyst. This paper further describes a method for splitting water using the catalyst.

Description

Single-crystal TA3N5 nanoparticles modified with MOx co-catalyst, catalyst, method for using the catalyst in water splitting, and method for manufacturing the catalyst. The use of solar energy in the presence of photocatalysts to split water to produce hydrogen and oxygen has been investigated as a potential means of clean, large-scale fuel production. With growing concerns about global warming, hydrogen fuel production is receiving increasing attention. Methods such as photocatalytic water splitting are being researched for the production of hydrogen (a clean combustion fuel). Water splitting is particularly promising due to its use of water (an inexpensive and renewable resource). Photocatalytic water splitting offers the simplicity of producing hydrogen from water using a catalyst and sunlight. In contrast to the two-step system of photovoltaic power generation and subsequent water electrolysis, photocatalytic water splitting involves direct contact between a photocatalyst and water. The photocatalyst is either in a homogeneous environment relative to water (the photocatalyst is suspended in the water) or in a heterogeneous phase relative to water (the photocatalyst is bonded to a surface in contact with water). Examples of heterogeneous photocatalytic processes include those described in US10,744,495 and US2014 / 0174905, and these patented methods can be used with the catalyst of this invention and are incorporated herein by reference in their entirety. Whether homogeneous or heterogeneous, photocatalytic water splitting is more efficient than the two-step process of water electrolysis. The primary measure of photocatalyst effectiveness is quantum yield (QY), which is: QY (%) = (photochemical reaction rate) / (photon absorption rate) × 100%. This quantity reliably determines the effectiveness of the photocatalyst. Generally, the best photocatalysts exhibit both high quantum yield and high gas release rates. Almost all reported photocatalytic water splitting systems are affected by low QY in the visible light region (e.g., rarely exceeding 3% at 420 nm), which significantly hinders any potentially viable applications. To address the growing global energy shortage and environmental degradation, artificial photosynthesis (photocatalytic water splitting and CO2 reduction) is being developed. 2. Reduction is a promising method for converting solar energy into high-value-added chemical energy (Chen, XB; Li, C.; Grätzel, M.; Kostecki, R.; Mao, SS Nanomaterials for renewable energy production and storage. Chem. Soc. Rev. 2012, 41, 7909−7937 and Wang, Z.; Li, C.; Domen, K. Recent developments in heterogeneous photocatalysts for solar-driven overall water splitting. Chem. Soc. Rev. 2019, 48, 2109−2125). Photocatalytic water splitting generally involves two independent reaction pathways, producing hydrogen and oxygen: 2H+ 2O => 2H 2+ O 2. Photocatalysts can enhance the catalytic reduction reactions of the hydrogen pathway and / or enhance the catalytic oxidation reactions of the oxygen pathway. It is desirable to use one or more photocatalysts that can simultaneously promote both the hydrogen and oxygen pathways, and to do so in an efficient manner. Water oxidation (four-electron transfer and O=O bond formation) is not only the decomposition of water into H+. 2 and O A crucial step in step 2 is CO. 2. Key steps in the reduction to carbon-containing chemicals (Wang, Y.; Suzuki, H.; Xie, J.; Tomita, O.; Martin, DJ; Higashi, M.; Kong, D.; Abe, R.; Tang, JW) Mimicking natural photosynthesis: solar to renewable H 2Fuel synthesis by Z‑scheme water splitting systems. Chem. Rev. 2018, 118, 5201−5241; and Wang, Z.; Teramura, K.; Hosokawa, S.; Tanaka, T. Highly efficient Photocatalytic conversion of CO 2 into solid CO using H 2O as a reductant over Ag-modified ZnGa 2O 4. J. Mater. Chem. A 2015, 3, 11313−11319 and Kudo, A; Miseki, Y. Heterogeneous photocatalyst materials for water splitting. Chem. Soc. Rev. 2009, 38, 253−278.) Since visible light (wavelengths between 400 nm and 800 nm) constitutes a large portion of the solar spectrum, developing semiconductor photocatalysts capable of reacting under broad visible light irradiation is crucial for achieving desired solar energy conversion efficiency. The use of Ta... 3N 5 is used for solar water splitting because of its simple chemical composition, narrow band gap energy (2.1 eV), and suitable band position across the water redox potential. Ta has been reported. 3N 5 can release H from the half-reaction 2 or O 2(Yuliati, L.; Yang, J. H.; Wang, X. C.; Maeda, K.; Takata, T.; Antonietti, M.; Domen; and Highly active tantalum(V) nitride nanoparticles prepared from a mesoporous carbon nitride template for photocatalytic hydrogen evolution under visible light irradiation. J. Mater. Chem. 2010, 20, 4295−4298; and Qi, Y.; Chen, S. S.; Li, M. R.; Ding, Q.; Li, Z.; Cui, J. Y.; Dong, B. B.; Zhang, F. X.; Li, C. Achievement of visible-light-driven Z-scheme overall water splitting using barium-modified Ta 3N 5as a H 2-evolving photocatalyst. Chem. Sci. 2017, 8, 437−443; and Hou, J. G.; Wu, Y. Z.; Cao, S. Y.; Liang, F.; Lin, Z. S.; Gao, Z. M.; Sun, L. C. In situ phase-induced spatial charge separation in core-shell oxynitride nanocube heterojunctions realizing robust solar water splitting. Adv. Energy Mater. 2017, 7, 1700171; and Nurlaela, E.; Ould-Chikh, S.; Llorens, I.; Hazemann, J.; Takanabe, K. Establishing efficient cobalt-based catalytic sites for oxygen evolution on a Ta 3N 5 photocatalyst. Chem. Mater. 2015, 27, 5685−5694) and one-step activated total water splitting (Wang, Z.; Inoue, Y.; Hisatomi, T.; Ishikawa, R.; Wang, Q.; Takata, T.; Chen, SS; Shibata, N.; Ikuhara, Y.; Domen, K. Overall water splitting by Ta 3N 5nanorod single crystals grown on the edges of KTaO 3particles. Nat. Catal. 2018, 1, 756−763.). Due to its water oxidation ability, Ta 3N 5. O in Z-type water splitting and photoelectrochemical water splitting 2. Significant improvements were achieved in the release of the product (Tabata, M.; Maeda, K.; Higashi, M.; Lu, D.; Takata, T.; Abe, R.; Domen, K. Modified Ta 3N 5powder as a photocatalyst for O 2evolution in a two-step water splitting system with an iodate / iodide shuttle redox mediator under visible light. Langmuir 2010, 26, 9161−9165; and Ma, SS; Maeda, K.; Hisatomi, T.; Tabata, M.; Kudo, A.; Domen, K. A redox-mediator-free solar-driven Z-scheme water-splitting system consisting of modified Ta 3N 5as an oxygen-evolution photocatalyst. Chem. Eur. J. 2013, 19, 7480−7486; and Liu, GJ; Ye, S.; Yan, PL; Xiong, FQ; Fu, P.; Wang, ZL; Chen, Z.; Environ. Sci. 2016, 9, 1327−1334 (2016); and Zhong, M.; Hisatomi, T.; Sasaki, Y.; Suzuki, S.; Teshima, K.; Nakabayashi, M.; Shibata, N.; Nishiyama, H.; Katayama, M.; Yamada, T.; Domen, K. Highly active GaN-stabilized Ta 3N 5thin-film photoanode for solar water oxidation. Angew. Chem. Int. Ed. 2017, 56, 4739−4743). Highly expecting a high-quality Ta 3N 5. Photocatalysts are used to effectively enhance the separation of photoexcited charges and the migration of electrons and holes to surface sites for photocatalytic reactions. (Learn about Ta...) 3N 5. Photocatalysts are generally composed of powdered Ta, which consists of aggregated polycrystalline microparticles with crystal defects and impurity energy levels. 2O 5 precursor in NH 3. Nitriding under high temperature and long duration results in crystal defects and impurity energy levels that are detrimental to photocatalytic water oxidation activity. Modification with alkaline metals or magnesium oxide to improve the oxidation process is necessary. 2O 5. Pre-adjustment Ta 3N The morphology and surface properties of 5 promote efficient photocatalysis of O 2. Required for release. When the lattice spacing is close to Ta 3N 5 lattice spacing of KTaO 3. When potassium components, which are easily vaporized at high temperatures, are used as unique starting metal oxides, in short NH4+... 3. Minimizing the defect state of Ta in the nitriding process 3N 5 nanometer rod single crystal in KTaO Rapid growth on 3 cubes and exhibited in one-step visible light-driven total water splitting while releasing H 2 and O 2. This confirms its use in the synthesis of Ta. 3N Before 5, the body was operating Ta 3N The morphology, crystallinity, nanostructure, and defect states of Ta particles play a fundamental role in achieving efficient conversion of solar energy into chemical energy. Metallic Ta particles can be considered as well-grown and crystallized Ta particles. 3N 5. Promising materials for photocatalysts, because Ta metal and NH 3. The oxidation reaction under high-temperature nitriding differs from that of Ta. 2O O- to -N substitution of the precursor significantly shortens the nitriding process. Single-phase Ta production from Ta metal powder has been reported. 3N 5. In the same short-term nitriding process, no Ta was produced. 2O 5. In addition, through simple NH 3. The nitriding process synthesizes doped nanoparticles Ta from Ta metal nanoparticles. 3N 5 single crystals exhibit significantly enhanced photocatalytic water reduction activity (H 2. Production), demonstrating the advanced availability of nanoscale Ta metal precursors. (Ma, S.; Hisatomi, T.; Maeda, K.; Moriya, Y.; Domen, K. Enhanced water oxidation on Ta 3N 5通过碱金属盐改性的光催化剂。《美国化学会志》2012年,第134卷,19993−19996页;以及陈,S.S.;沈,S.;刘,G.J.;齐,Y.;张,F.X.;李,C. CoOx / Ta的界面工程 3N 5用于在可见光照射下实现前所未有的水氧化性能的光催化剂。《德国应用化学》2015年,第54卷,3047−3051页;以及铃木,S.;安藤,R.;松井,Y.;石濑,K.;汤田,K.;手岛,K. 通过Ta颗粒经由Na的自牺牲模板样转化制备的棱柱形Ta3N5组成的球体 2CO 3通量。《晶体工程通讯》2020年,第22卷,5122−5129页;以及肖,J.D.;韦基佐,J.J.;久富智,T.;拉贝阿,J.;中林,M.;王,Z.;肖,Q.;李,H.H.;潘,Z.H.;克劳斯,M.;尹,N.;史密斯,G.;柴田,N.;布吕克纳,A.;山形,A.;高田,T.;多门,K. 同时调节Ta的缺陷和表面性质 3N 5nanoparticles by Mg-Zr codoping for significantly accelerated photocatalytic H 2evolution. J. Am. Chem. Soc. 2021, 143, 10059−10064). Because of Ta 3N Its excellent visible light absorption and single-crystal composition make it a promising photocatalyst for solar water splitting. However, conventional Ta, derived from oxide precursors... 3N 5. Photocatalysts generally have aggregated polycrystalline microparticles with defect states and grain boundaries, which limits the significant enhancement of photocatalytic water oxidation activity. Therefore, it is necessary to provide an improved Ta 3N 5 nanoparticles and catalysts that can provide single-crystal nanoparticles and / or provide improved catalytic properties (such as, but not limited to, improved photocatalytic water oxidation activity). Therefore, there is a need in the industry for improved nanoparticles, and in particular improved tantalum nitride, for use as catalysts and in methods for water splitting and / or other applications. This application claims the right of U.S. Provisional Patent Application No. 63 / 310,237, filed February 15, 2022, pursuant to 35 USC §119(e), which is incorporated herein by reference in its entirety. Therefore, one feature of the present invention is to provide a novel tantalum nitride, and more particularly a novel Ta 3N 5 nanometer particles, such as single-crystal Ta 3N 5-nanometer particles. Another feature is that it provides Ta that can be used with at least one co-catalyst. 3N 5-nanometer particles. Another feature of the present invention is the provision of a catalyst, such as one used for water oxidation to produce O. 2. Another feature of the present invention is that it provides a single catalyst, such as for water oxidation to produce O. 2. It is also used for water reduction to produce H+. 2. Another feature of the present invention is the provision of a catalyst, such as a mixture of a water oxidation catalyst and a water reduction catalyst, for the production of O2 by water oxidation. 2. It is also used for water reduction to produce H+. 2. Another feature of the present invention is that it provides a water splitting catalyst. Another feature of the present invention is that it provides a method for water splitting using nanoparticles, such as those in the form of a catalyst. Another feature of this invention is that it provides a method for manufacturing novel tantalum nitride and catalysts. Further features and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practicing the invention. The objectives and other advantages of the invention will be realized and obtained by means of the description and the elements and combinations particularly pointed out in the appended claims. To achieve these and other advantages and for the purposes of the invention, as embodied and broadly described herein, part of the invention relates to tantalum nitride, particularly Ta 3N 5, and containing or derived from Ta 3N 5. Products made from catalysts, such as, but not limited to, catalysts. This invention also relates to metal oxides (such as CoO) x Co-catalyst, wherein O x Ta (indicating that it is a part of the oxide of cobalt oxide) modified 3N 5-nanometer particles. The present invention further relates to metal oxides (such as CoO) x Co-catalyst, wherein O x This indicates that single-crystal Ta is modified with an oxide (which is a part of cobalt oxide). 3N 5-nanometer particles. Furthermore, this invention relates to a catalyst containing or processed by a metal catalyst (such as CoO). x Co-catalyst, wherein O x Ta (indicating that it is a part of the oxide of cobalt oxide) modified 3N Photocatalysts using 5-nanometer particles (e.g., single crystals). Similarly, this invention relates to a catalyst comprising a metal oxide co-catalyst (such as CoO) xCo-catalyst) and single-crystal Ta modified by platinum and / or other metal catalysts distributed on the surface of these single-crystal nanoparticles. 3N 5-nanometer particles. Furthermore, this invention relates to a catalyst containing or being composed of Ta. 3N 5 nanometer particles (e.g., single crystals), 1) which are reacted with metal catalysts (such as CoO) x Co-catalyst, wherein O x This indicates that the oxide is a part of the cobalt oxide and that it is modified by one or two metals such as Zr and / or Mg (e.g., Ta). 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Zr or any combination thereof). The cocatalyst can be impregnated, attached, distributed or dispersed on or used with single-crystal nanoparticles. Furthermore, this invention relates to a mixture of catalysts, wherein the first catalyst is a water oxidation catalyst and the second catalyst is a water reduction catalyst. For example, the mixture may contain or be a metal catalyst (such as CoO) in which the first catalyst is present. x Co-catalyst, wherein O x Ta (indicating that it is a part of the oxide of cobalt oxide) modified 3N 5 nanometer particles (e.g., single crystals), and the second catalyst is precipitated by one or two metals such as Zr and / or Mg (e.g., Ta). 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Zr or any combination thereof) modification or doping. The present invention further relates to a catalyst comprising the single-crystal nanoparticles of the present invention and a metal oxide catalyst (e.g., CoO). xThe co-catalyst further comprises a co-catalyst (which may be platinum metal (Pt)) that is uniformly distributed or dispersed on single-crystal nanoparticles or mixed with or used in combination with nanoparticles. This invention further relates to a catalyst comprising the single-crystal nanoparticles of this invention and a metal co-catalyst (e.g., a CoOx co-catalyst) used as a water oxidation catalyst, in combination with a water reduction catalyst. For example, the water reduction catalyst for the reduction reaction may selectively use tantalum nitride single-crystal nanoparticles doped with at least one metal. The reduction reaction may use Ta 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof. The reduction reaction can use Ta. 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof and at least one co-catalyst (e.g., Pt). Furthermore, this invention relates to a water splitting method comprising the step of contacting water or other fluids with a catalyst (e.g., a photocatalyst) of this invention. The method may further comprise the use of another catalyst (e.g., a photocatalyst), wherein one catalyst is a water oxidation catalyst as described herein, and the other catalyst is a water reduction catalyst as described in U.S. Provisional Patent Application No. 63 / 184,816 or WO 2022 / 235721, filed May 6, 2021, which are incorporated herein by reference in their entirety. The two catalysts may be used as a mixture on the same single-crystal nanoparticle of this invention, or may be used as a mixture of nanoparticles and introduced or used in any order. Furthermore, this invention relates to a water splitting method comprising the step of contacting water or other fluids with a catalyst (e.g., a photocatalyst) of this invention. A single / same catalyst has a dual function, namely, a water oxidation catalyst as described herein and a water reduction catalyst as described in U.S. Provisional Patent Application No. 63 / 184,816 or WO 2022 / 235721, filed May 6, 2021, which are incorporated herein by reference in their entirety. This invention also relates to a method for manufacturing the nanoparticles or catalyst of this invention, comprising a nitriding process of spherical tantalum powder or tantalum aggregates containing salt, or flame-synthesized tantalum that is salt-encapsulated as needed, wherein the nitriding process includes NH4+. 3. Nitriding is carried out at 700 K or higher for 10 minutes to 4 hours or longer to form tantalum nitride, followed by a metal oxide co-catalyst (such as CoO). x ) is used as a cocatalyst for impregnating tantalum nitride. It should be understood that the foregoing general description and the following detailed description are merely exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. This invention relates to tantalum nitride nanoparticles, such as those derived from metal oxides (such as CoO). x Ta modified by co-catalyst 3N 5 nanometer particles. These nanometer particles can be used alone as a catalyst or as part of a catalyst. The catalyst can be used in various methods, such as water splitting methods. This invention further relates to a method for preparing these tantalum nitride nanometer particles and the catalyst. Preferably, via a metal oxide (such as CoO) x (Co-catalyst) modified tantalum nitride nanoparticles, such as Ta 3N 5-nanometer particle systems are used as catalysts for water oxidation. Tantalum nitride nanoparticles can be further modified for use as water reduction catalysts as explained herein. Tantalum nitride nanoparticles used as water oxidation catalysts can be used in combination with tantalum nitride nanoparticles used as water reduction catalysts. Dual catalysts can be used on the same tantalum nitride nanoparticle or as a mixture of tantalum nitride nanoparticles (combining tantalum nitride nanoparticles used as water oxidation catalysts with a mixture of tantalum nitride nanoparticles used as water reduction catalysts to form a mixture of the two types of nanoparticles). A specific example of tantalum nitride is Ta 3N 5. Other examples of tantalum nitride include, but are not limited to, Ta 4N 5. Ta 5N 6. Ta 2N and TaN, and generally TaN x , where x is in the range of 0.1 to 3. Tantalum nitride can be an n-type semiconductor, preferably with a narrow band gap and / or suitable energy positions of the conduction band and valence band across the water redox potential. The Ta of this invention 3N 5-nanometer particles can be single-crystal nanoparticles. The Ta of this invention 3N 5 nanometer particles can be modified by at least one cocatalyst (e.g., via the general formula MO). x Metal oxide modification, where M represents a metal and O x This refers to single-crystal nanoparticles (which are part of the oxide of the metal oxide). An example metal oxide includes CoO. x MnO x FeO x NiO x IrO x and RuO x While specific embodiments of CoOx are sometimes described herein as metal oxides, it should be understood that the details and discussions relating to CoOx also apply to other metal oxides used for the purposes of this invention. Wait for Ta 3N 5 nanometer particles can be monodisperse nanometer particles, such as single-crystal Ta. 3N 5. Monodisperse nanoparticles, where monodisperse refers to particles having approximately the same size. A monodisperse distribution can be defined as a group of nanoparticles whose particle sizes are within 20%, 10%, 5%, or 1% of each other. Particle size can be measured using a laser diffraction particle size analyzer (such as the Horiba Scientific Partica LA-960V2) or a dynamic light scattering particle size analyzer (such as the Horiba Scientific nanoPartica SZ-100V2 series). The nanoparticles of the present invention as described above or herein may be monodisperse nanoparticles and nanoparticles having a single crystalline phase. The crystalline particles of the present invention may be nanoparticles that are substantially free of or have no minor segregating phases within a detectable range, such as Ta, Ca, or similar trace phases. As a more specific example and with reference to a preferred embodiment, these nanoparticles may be made of CoO x Single-crystal Ta modified by co-catalyst 3N 5 nanometer particles, of which O x It indicates that it is an oxide of cobalt oxide. Metal oxide co-catalysts (such as CoO) x (Co-catalyst) in an amount sufficient to be used as a water oxidation catalyst, such as based on single-crystal Ta 3N At least 0.01 wt% of the total weight of 5 nanometer particles were impregnated into Ta 3N On 5 nanometer particles. This amount is based on Ta modified with metal oxide. 3N 5 nanometer particle photocatalysts (e.g., those with CoO) x Modified Ta 3N The total weight of the 5-nanometer particle photocatalyst may be at least 0.05 wt%, or at least 0.1 wt%, or at least 0.25 wt%, or at least 0.5 wt%, or higher, such as from 0.01 wt% to 1 wt% or higher, or from 0.05 wt% to 1 wt%. The CoO x The co-catalyst can be CoO, Co 2O, Co 2O 3 and / or Co 3O 4. or any combination thereof or mixture thereof. Single-crystal nanoparticles (e.g., modified by at least one co-catalyst, such as by at least one metal oxide (e.g., CoO) x Ta modified by co-catalyst 3N The 5-nanometer particles may have an apparent quantum yield of at least 5%, at least 7.5%, at least 9%, at least 10% at 420 nm, such as from 5% to 10% or higher at 420 nm. The present invention further relates to a catalyst (such as a photocatalyst) that is or contains single-crystal nanoparticles (e.g., modified by at least one co-catalyst, such as by at least one metal oxide (such as CoO)). x Ta modified by co-catalyst 3N 5 nanometer particles). Catalysts can be used in nitriding processes such as NH4+ 3. Nitriding-formed single-crystal nanoparticles. The catalysts of the present invention (such as photocatalysts) may have the ability to provide O2 concentrations of more than 200 μmol / h, more than 400 μmol / h, more than 600 μmol / h, or more than 700 μmol / h, such as from 200 μmol / h to 800 μmol / h. 2. The nature of yield. The catalyst of the present invention (such as a photocatalyst) may have the function of photocatalytic O 2. The release reaction (OER) provides the property of apparent quantum yield (AQY) in amounts exceeding 0.1%, such as from 0.1% to 9.4%, such as within 20%, 10%, or 5% of this 9.4% value. When the catalyst used also includes a water reduction catalyst (as part of the same catalyst or in combination with a water oxidation catalyst), as described herein, the catalyst of the present invention (such as a photocatalyst) may have the property of providing a solar-to-hydrogen (STH) energy conversion efficiency of more than 0.015%, such as from 0.015% to 0.1% or higher. When the catalyst used also comprises a water reduction catalyst (as part of the same catalyst or in combination with a water oxidation catalyst), as described herein, the catalysts of the present invention (such as photocatalysts) may have the ability to provide H+ ions from 5 µmol / h to 13 µmol / h, such as from 5 µmol / h to 13 µmol / h. 2. The nature of yield. When the catalyst used also contains a water reduction catalyst (as part of the same catalyst or in combination with a water oxidation catalyst), as described herein, the catalyst of the present invention (such as a photocatalyst) may have the function of photocatalytic H 2. The release reaction (HER) provides an apparent quantum yield (AQY) of more than 0.15%, such as from 0.15% to 0.54%, such as within 20%, 10%, or 5% of this 0.54% value. When the catalyst used also contains a water reduction catalyst (either as part of the same catalyst or in combination with a water oxidation catalyst), as described herein, the catalyst can provide more than 200 μmol / h, such as from 200 μmol / h to 800 μmol / h of O. 2. Yields and above 5 μmol / h, such as H2 from 5 μmol / h to 13 μmol / h 2. The nature of the yield, and its application in photocatalysis of O The OER (Organic Release Reaction) provides apparent quantum yields exceeding 0.1%, ranging from 0.1% to 9.4%, and is beneficial for photocatalytic H2O. The HER release reaction provides apparent quantum yields (AQY) exceeding 0.15%, such as from 0.15% to 0.54%. The catalyst can further possess the STH properties described herein. The present invention further relates to a catalyst comprising single-crystal nanoparticles that have been further modified or comprised of platinum and / or other metal catalysts distributed on the surface of such single-crystal nanoparticles (e.g., modified with at least one co-catalyst, such as with metal oxides (e.g., CoO)). x Ta modified by co-catalyst 3N 5 nanometer particles). The present invention further relates to the use of catalysts comprising the single-crystal nanoparticles of the present invention and metal oxide co-catalysts (e.g., CoOx co-catalysts) as water oxidation catalysts and in combination with water reduction catalysts (as described herein) in photocatalytic water splitting. The catalyst (such as a photocatalyst) may be at least a catalyst for water oxidation, and the catalyst may include the crystalline nanoparticles described herein (e.g., modified by at least one co-catalyst, such as by a metal oxide (such as CoO)). x Ta modified by co-catalyst 3N (5 nanometer particles), basically composed of, composed of or one of them. For example, Ta 3N 5-nanometer particle photocatalysts for the extraction of sacrificial AgNO3 3. O released from solution 2. It has high photocatalytic performance. The catalyst of this invention can have a higher content than the original Ta. 3N 5. Higher photocatalytic water oxidation activity (e.g., under visible light irradiation). Higher activity may be 5% or higher, or 10% or higher, or 15% or higher. For example, the nanoparticles or catalysts of the present invention (e.g., modified by at least one co-catalyst, such as by a metal oxide (e.g., CoO) x Ta modified by co-catalyst 3N 5 nanometer particles may have an O content of at least 200 μmol / h, or at least 300 μmol / h, or at least 450 μmol / h. 2. Release rate, such as from 200 μmol / h to 800 μmol / h, or from 200 μmol / h to 700 μmol / h, or from 200 μmol / h to 600 μmol / h, or from 200 μmol / h to 500 μmol / h. When more than one type of tantalum nitride exists in a swarm of nanoparticles, the distribution of two or more different tantalum nitrides can be uniform or non-uniform. For example, Ta 3N 5 can be present based on the highest weight percentage of the total weight of all present tantalum nitride. Optionally, only one type of tantalum nitride may be present in the nanoparticle swarm. The single-crystal nanoparticles of this invention can exhibit properties similar to black titanium nitride (such as black titanium Ta). 3N 5) Related single-phase X-ray diffraction (XRD) patterns. The single-crystal nanoparticles of this invention can have various shapes. For example, the nanoparticles can have shapes that make them appear as rod-shaped and / or spherical particles, such as monodisperse rod-shaped nanoparticles or monodisperse spherical particles. When nanoparticles are nanorod particles, the nanorod particles can have a certain length. The length can be from 50 nm to 500 nm or higher, such as from 50 nm to 450 nm, from 50 nm to 400 nm, from 50 nm to 350 nm, from 50 nm to 300 nm, from 50 nm to 250 nm, from 50 nm to 200 nm, from 50 nm to 150 nm, from 75 nm to 500 nm, from 100 nm to 500 nm, from 125 nm to 500 nm, from 150 nm to 500 nm, from 175 nm to 500 nm, from 200 nm to 500 nm, from 225 nm to 500 nm, from 250 nm to 500 nm, from 275 nm to 500 nm, from 300 nm to 500 nm, and so on. The length can be regarded as the average length. Length (and width) measurements can be performed using images taken with a scanning electron microscope. At least three images should be analyzed for each sample, and at least 10 particles should be measured for each image. Overall, the length and width of at least 30 particles should be measured, and the average length and average width should be taken. When nanoparticles are used to form nanorods, such nanorods may have an aspect ratio (length / width) of at least 1.2 (e.g., at least 1.3, or at least 1.4, or at least 1.5, or at least 1.7, or at least 2 or at least 2.5, or at least 3, or at least 4, such as from 1.2 to 4 or higher, or from 1.3 to 4, or from 1.4 to 4 and so on). When the nanoparticles are spherical, the spherical nanoparticles can have an average particle size (e.g., diameter) of 20 nm to 500 nm or higher, such as from 50 nm to 500 nm or higher, such as from 50 nm to 450 nm, from 50 nm to 400 nm, from 50 nm to 350 nm, from 50 nm to 300 nm, from 50 nm to 250 nm, from 50 nm to 200 nm, from 50 nm to 150 nm, from 75 nm to 500 nm, from 100 nm to 500 nm, from 125 nm to 500 nm, from 150 nm to 500 nm, from 175 nm to 500 nm, from 200 nm to 500 nm, from 225 nm to 500 nm, from 250 nm to 500 nm, from 275 nm to 500 nm, from 300 nm to 500 nm, and so on. The measurement / method can be performed using a laser diffraction particle size distribution analyzer or a dynamic light scattering particle size distribution analyzer. Alternatively, tantalum nitride (e.g., Ta) 3N 5) Can have Ta 3N The surface Ta atomic ratio of the form (N−Ta−N) is greater than 90 at% (e.g., such as 91 at% or higher, or 92 at% or higher, or 95 at% or higher, or from 91 at% to 99 at% or from 91 at% to 98 at%, or 92 at% to 98 at%, or 93 at% to 98 at%, or 94 at% to 98 at%). Alternatively, tantalum nitride (e.g., Ta) 3N 5) Can have Ta 3+ The surface atomic ratio of Ta in the form of [formula] is less than 1 at% (e.g., 0.9 at% or less, or 0.8 at% or less, or 0.5 at% or less, such as 0.001 at% to 0.9 at% or 0.01 at% to 0.5 at%). [Form of Ta] 3+ The atomic ratio of Ta on the surface of the form is undetectable or below 0.001 at. Optionally, tantalum nitride (e.g., Ta) 3N 5) Can have TaO x N yThe atomic ratio of Ta on the surface of the (O−Ta−N) form is 2 at% or higher. This atomic ratio can be from 2 at% to 5 at%. Here, x and y make N / O preferably greater than 2, or greater than 3, or greater than 4, or greater than 4.5 or greater than 4.8. The crystalline particles of the present invention may have a charge imbalance such that the oxygen to anion (O / N+O) molar ratio is 3.0% or higher or 4.0% or higher, such as from 3.0% to about 18% or from 5% to about 18%, or from about 7% to about 18%, or from about 10% to about 18%, or from about 12% to about 18%, or from 15% or higher. Optionally, tantalum nitride (e.g., Ta) 3N 5) May have a charge imbalance that results in an oxygen to anion (O / N+O) molar ratio of 4.0% or higher (e.g., such as from 5.0% to about 18%, or from 6.0% to 18%, or from 7.0% to 18%, or from 8.0% to 18%, or from 9.0% to 18%, or from 10% to 18%, and such molar ratios). Optionally, tantalum nitride (e.g., Ta) 3N 5) Tantalum nitride may be one or more of the following defective species that are substantially absent or not present within the detectable range: reducing species, such as Ta 3+ Or Ta 4+ , or V N Or O N The phrase "substantially non-existent" as used herein and throughout this document (unless otherwise stated) may be less than 15 at% or less than 10 at% or less than 5 at% or less than 2.5 at% or less than 1.5 at% or less than 1 at% or less than 0.5 at% or less than 0.2 at%, or less than 0.1 at%, or less than 0.05 at%, or less than 0.01 at%, or less than 0.001 at%. N This indicates a nitrogen vacancy, which can be represented by V. N •••、V N ••、V N • and V N ø. And V N •••、V N ••、V N • and V N ø represents V with zero, one, two, and three trapped electrons, respectively. N V, and only has unpaired electrons N ••and V N ø can be EPR active. O N Indicates oxygen impurities (examples contain O) 2- ). The tantalum nitride of this invention can be used alone or as a catalyst, or optionally as part of a catalyst. As a catalyst, the tantalum nitride of this invention can be used with one or more co-catalysts, and / or modified and / or doped with one or more metals and / or impregnated or surface-coated with one or more metals. The catalyst of this invention can be a photocatalyst. This photocatalyst can be active for various light waves or light regions, such as ultraviolet light and / or visible light (i.e., the visible light region). The co-catalyst may be at least one metal oxide, such as at least one CoO alone. x The cocatalyst may be a metal cocatalyst or both. The cocatalyst may be, contain, or further contain platinum (Pt). The cocatalyst may be, contain, or further contain metals such as, but not limited to, gold, platinum, cobalt, palladium, silver, nickel, or any combination thereof. The cocatalyst may be, contain, or further contain Cr. 2O 3. Cocatalysts such as metal cocatalysts (e.g., Pt) can be used with another cocatalyst (e.g., CoO). x Co-catalyst or Cr 2O 3) Use in combination. The tantalum nitride of the present invention can be used as a catalyst (such as a photocatalyst) to produce oxygen by splitting water and can be used in combination with a second catalyst (such as a photocatalyst) that can produce hydrogen by splitting water. Therefore, optionally, the present invention may be a combination of two catalysts, namely a water oxidation catalyst and a water reduction catalyst. These two catalysts can be used together as a mixture. The two catalysts can be used sequentially—specifically, the water oxidation catalyst is used followed by the water reduction catalyst, or vice versa. Both catalysts can be used so that they can be added individually to the water splitting reaction, but they can also coexist during the water splitting reaction. When two catalysts are used, they may be used in equal amounts (by weight), or one catalyst may be used in greater quantities than the other. For example, the weight ratio of water oxidation catalyst to water reduction catalyst may be from 10:1 to 1:10, such as from 7.5:1 to 1:7.5, or from 5:1 to 1:5, or from 3:1 to 1:3, or from 2:1 to 1:2, or from 1.5:1 to 1:1.5, or from 1.2:1 to 1:1.2, or from 1.1:1 to 1:1.1, and such weight ratios. Optionally, the tantalum nitride of the present invention can be used as a dual catalyst, such as a dual photocatalyst, to produce oxygen from water splitting and also to produce hydrogen from water splitting. In this option, the tantalum nitride is modified in at least two ways, thereby achieving two catalytic functions. The tantalum nitride is modified as described herein (e.g., modified with at least one co-catalyst, such as with at least one metal oxide (e.g., CoO)). x (co-catalyst) modification), and also through one or two metals such as Zr and / or Mg (e.g., Ta). 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Zr or any combination thereof) modification or doping. And as another example, all Mg 2+ and / or Zr 4+ All cations are present in Ta 3N In a 5-fold lattice. Regarding further modification of the sample, tantalum nitride can be only Ta 3N 5:Mg+Zr. Tantalum nitride can be Ta-only. 3N 5:Mg. Tantalum nitride can be Ta-only. 3N 5: Zr. Each tantalum nitride can cause Mg and / or Zr to exist as cations in Ta. 3N In a 5-fold lattice. Regarding the dual catalyst and water reduction function, when tantalum nitride is or contains Ta 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: When Zr or any combination thereof is used, tantalum nitride may have a magnesium-to-cation ratio (e.g., Mg / (Ta+Mg+Zr)) and a Zr-to-cation ratio (e.g., Zr / (Ta+Mg+Zr)) of up to 9.0 mol.% and 10.2 mol.%, respectively. The magnesium-to-cation ratio may be 1 to 9 mol%, or from 2 to 9 mol%, or from 3 to 9 mol%, or from 4 to 9 mol%, or from 5 to 9 mol%, or from 6 to 9 mol%. The Zr-to-cation ratio may be 1 to 10.2 mol%, or from 2 to 10 mol%, or from 3 to 10 mol%, or from 4 to 10 mol%, or from 5 to 10 mol%, or from 6 to 10 mol%, or from 7 to 10 mol%. Modifiable tantalum nitride can be used for water reduction, transforming it into TaN. x :M1 or TaN x M1+M2 or any combination thereof, wherein x is in the range of 0.1 to 3, M1 and M2 represent metal cations (e.g., Mg, Zr, Li, Sc, Ti, Hf, Al or Ga) and M1 is different from M2. The tantalum nitride of the present invention can be used alone or as a catalyst (such as a photocatalyst) and has the ability to decompose water without the assistance of a co-catalyst. Using one or more co-catalysts or a metal system is preferred. When both functions are required, namely water oxidation and water reduction, it is preferable to include metals such as Pt and, if necessary, Cr. 2O 3 or other metal oxides (e.g., Pt / Cr formed on Pt) 2O 3. Uniform thin-layer Cr core-shell nanostructure 2O 3) The loading of metals such as Pt or other metals may be at least 0.1 wt%, at least 0.5 wt%, at least 0.9 wt%, or at least 1 wt% based on the weight of the catalyst. The tantalum nitride of the present invention can be used alone or as a catalyst (such as a photocatalyst) and has the ability to decompose water without the use of sacrificial reagents. Optionally, the tantalum nitride of the present invention may be used as a catalyst, alone or together with one or more co-catalysts (such as photocatalysts) as described herein, and has the ability to split water, and uses one or more sacrificial agents (e.g., sacrificial electron donors), such as, but not limited to, AgNO3. 3. The tantalum nitride of the present invention can be used alone or as a catalyst (such as a photocatalyst) and has the ability to decompose water under ultraviolet light or visible light. The cocatalyst can be distributed or dispersed on nanoparticles, such as uniformly distributed or dispersed on single-crystal nanoparticles. Alternatively or additionally, the cocatalyst can be mixed with or combined with nanoparticles in any way. Preferably, the cocatalyst is uniformly distributed on the surface of the single-crystal nanoparticles (e.g., the weight variance of the cocatalyst at any location on the surface is ±10%). Optionally, aggregation of the cocatalyst or aggregation of the cocatalyst and nanoparticles is undetectable. The present invention further relates to a method for manufacturing the nanoparticles of the present invention. The manufacturing catalyst (e.g., Ta) 3N The method for 5-nanometer particles may include or involve a mild nitriding process on spherical tantalum powder or salt valve metal aggregates (such as salt-containing aggregates such as tantalum aggregates with NaCl). "Mild nitriding" may be or include, or involve, a process that can be performed on a gas stream (such as NH4+). 3) Nitriding at high temperatures (such as 700 K or higher) or other temperatures (e.g., 700 K to 1300 K, 725 K to 1175 K, 750 K to 1175 K, 775 K to 1300 K, 800 K to 1300 K, 850 K to 1300 K, 900 K to 1300 K, 925 K to 1175 K, or 773 K to 1223 K). This method can be carried out at temperatures from 700 K to 1300 K or from 900 K to 1150 K for 10 minutes to 40 hours or longer, or from 1 hour to 8 hours, or from 8 hours to 32 hours or longer. Methods for manufacturing tantalum nitride may include or involve converting metallic tantalum (Ta) into tantalum nitride (e.g., Ta2). 3N 5). Tantalum can be spherical tantalum powder (such as having an aspect ratio of 1.4 to 1 or 1.2 to 1, measured by measuring the diameter of the particles and the longest diameter to the shortest diameter) or flame-synthesized tantalum, which may be encapsulated with salts such as NaCl as required. The conversion to tantalum nitride can be accomplished through a nitriding step, such as, but not limited to, in a gas stream (such as NH4+). 3) Nitriding tantalum at high temperatures (such as 700 K or higher) or other temperatures (e.g., 700 K to 1300 K, 725 K to 1175 K, 750 K to 1175 K, 775 K to 1300 K, 800 K to 1300 K, 850 K to 1300 K, 900 K to 1300 K, 925 K to 1175 K, or 773 K to 1223 K). This method may be performed at temperatures of 700 K to 1200 K or 900 K to 1150 K for 10 minutes to 40 hours or longer, or from 1 hour to 8 hours, or from 8 hours to 32 hours or longer. The method may then include impregnating tantalum nitride with at least one co-catalyst, such as at least one metal oxide (such as a CoOx co-catalyst) or a precursor thereof. Regarding the nitriding step, the gas used in the gas stream can be a nitrogen-containing gas, such as NH4+. 3. The gas flow rate may be 10 ml / min or higher, 100 ml / min or higher, 150 ml / min or higher, or 200 ml / min or higher, wherein the flow rate is measured at room temperature (25°C) and room pressure (1 atm). The amount of tantalum converted to tantalum nitride in the nitriding step may be 0.01 g or more, 0.1 g or more, 1.0 g or more, or 10.0 g or more. Tantalum can be used as follows. The manufacturing method may involve tantalum as the starting material, and the production process may include flame synthesis or sodium / halide flame encapsulation (SFE). Techniques suitable for preparing the starting tantalum powder used in this invention using the SFE process are described in U.S. Patent Nos. 5,498,446 and 7,442,227, which are incorporated herein by reference in their entirety. See also Barr, JL et al., “Processing salt-encapsulated tantalum nanoparticles for high purity, ultra high surface area applications”, J. Nanoparticle Res. (2006), 8:11–22. An example of a chemical method for producing metal powders using the SFE process of the '446 patent is as follows, where “M” refers to a metal, such as Ta:MCl. x +XNa+ inert gas → M+XNaCl+ inert gas. Tantalum pentachloride is an example of a tantalum halide, which can be used as a reactant MCl in this chemistry. xArgon can be used as an inert and carrier gas. Initially, particles (e.g., Ta) are generated in the flame and grow by solidification, while the salt remains in the gas phase. The salt condenses onto and / or around the Ta particles, heat is lost, and uncovered core particles can be removed by the salt particles. The tantalum used can be in powder form, such as powder obtained through the SFE process without any salt encapsulation or coating. The tantalum used can be in the form of powder, such as powder obtained by the SFE process and containing a salt layer or encapsulation, such as NaCl / Ta powder. Using at least one co-catalyst (such as at least one metal oxide, such as CoO) x Titanium nitride impregnation with a co-catalyst or its precursor can be achieved by using a metal precursor, such as a Co precursor, such as, but not limited to, Co(NO3)2. 3) 2∙6H It is achieved through 2O. Other examples of metallic precursors include, but are not limited to, Mn(NO). 3) 2∙(H 2O) n Fe(NO) 3) 3∙(H 2O) n ,Ni(NO 3) 2∙(H 2O) n ,Ru(NO 3) 3∙(H 2O) n CoCl 2∙(H 2O) n MnCl 2∙(H 2O) n FeCl 3∙(H 2O) n NiCl 2∙(H 2O) n IrCl 3∙(H 2O) n and RuCl 3∙(H 2O) n . Methods for manufacturing catalysts using cocatalysts may include or involve multiple cocatalyst supports (e.g., CoOx and Pt supports) on single-crystal nanoparticles. Each unique cocatalyst can be used to catalyze the same or different chemical reactions. For example, single-crystal nanoparticles may have a first cocatalyst support for catalyzing water oxidation (producing oxygen) and a second cocatalyst support for catalyzing water reduction (producing hydrogen). Ta modified with CoOx cocatalyst 3N The method for 5-nanometer particles can be achieved by impregnation, followed by application in NH4+. 3. The flow is completed through heat treatment. Generally speaking, for example, Ta 3N 5. The powder can be immersed in a metal precursor (such as Co(NO)) containing the desired amount or quantity. 3) 2∙6H Ta is added to an aqueous solution as a Co precursor. This forms a slurry. The slurry can be continuously stirred for a period of time (e.g., 1 to 5 minutes or longer) using ultrasonic treatment (e.g., high-intensity ultrasonic treatment) or other similar dispersion methods to allow Ta to disperse. 3N 5. The powder is completely dispersed in the metal precursor solution, such as Co(NO3)2. 3) 2. The modified nanoparticles can then be recovered by any technique, such as drying in a hot water bath. The resulting powder mixture can be heated at, for example, 500 K or higher, such as 773 K for 1 h or other times in NH4+. 3 airflow (100 mL min) −1 Metal oxide Ta is obtained by heating at either a lower or higher flow rate. 3N 5-nanometer particle photocatalysts, such as Ta modified with CoOx 3N 5-nanometer microparticle photocatalyst. The above method can be applied to other Co precursors and / or other metal precursors to modify tantalum nitride with this type of cocatalyst. Cocatalyst loading may involve or include the deposition of one or more cocatalysts (e.g., Pt) via an impregnation reduction (IMP) method. This method involves using a cocatalyst-containing compound or cocatalyst precursor (e.g., a Pt-containing compound or Pt precursor such as H₂). 2PtCl 6) Disperse tantalum nitride (with or without a first cocatalyst) to form a slurry, which can be heated with hot water vapor (such as steam) until dry. The powder is then placed in H... 2 / N 2 airflow (H) 2: 20 mL / min; N 2:200 mL / min) and heated at 250 °C for 1 h to obtain tantalum nitride supported on a co-catalyst. Co-catalyst loading (e.g., Pt loading) may involve or include the deposition of a co-catalyst (e.g., Pt) by in-situ photodeposition (PD). In this method, a co-catalyst precursor (e.g., a Pt precursor) may be added to an aqueous solution containing tantalum nitride nanoparticles (with or without a first co-catalyst). The co-catalyst (e.g., Pt) may be in-situ loaded onto the tantalum nitride nanoparticles under photocatalytic reaction conditions. Co-catalyst loading (e.g., Pt loading) can be a combination of IMP and PD methods. For example, co-catalyst loading (e.g., Pt loading) can be performed using a step-by-step method. The IMP-PD step-by-step method may involve depositing a co-catalyst (e.g., Pt) as a seed crystal via IMP (first step) and further growing the co-catalyst seed crystal (e.g., Pt) via in-situ PD (second step). In the combination of IMP and PD methods, the co-catalyst loading (e.g., Pt loading) by photodeposition (PD) can account for 70% to 95% of the total catalyst loading (by wt% of co-catalyst) (e.g., Pt loading of wt% Pt). The catalyst of the present invention can be used in methods for decomposing water or other fluids (such as aqueous fluids, wherein the fluid system refers to liquids or gases) and thereby producing, for example, hydrogen (e.g., in the form of hydrogen gas or hydrogen protons) and also oxygen (e.g., in the form of oxygen or oxygen molecules). The nanoparticles of this invention (and metal oxides such as CoOx) are particularly suitable for the water splitting process that produces oxygen, and can be used in combination with catalysts that are particularly suitable for the water splitting process that produces hydrogen. The catalysts (one for producing oxygen and one for producing hydrogen) can be used together or in any order. By design, the same catalyst can be a dual-purpose catalyst and perform both functions, namely, water splitting to produce oxygen and hydrogen. More specifically, the present invention further relates to a method for catalytically splitting water into hydrogen and oxygen elements, wherein an oxidation reaction produces O. 2. Contains catalysts described herein (e.g., modified with at least one co-catalyst, such as with metal oxides (e.g., CoO)). x Ta modified by co-catalyst 3N Any of the following (5 nanometer particles). The method of catalytically decomposing water into hydrogen and oxygen elements, except for oxidation reactions to produce O2. 2. In addition, it may further include the use of any of the catalysts (i.e., water reduction catalysts) described in U.S. Provisional Patent Application No. 63 / 184,816, filed May 6, 2021, or WO 2022 / 235721 to carry out a reduction reaction to produce H. 2. These cases are incorporated herein by reference in their entirety. Details and discussion of the preparation and use of the same water reduction catalysts and methods described in U.S. Provisional Patent Application No. 63 / 184,816, filed May 6, 2021, or WO 2022 / 235721, may be used herein to modify or incorporate into the catalysts of the present invention (in the same catalyst or in combination with a water oxidation catalyst). Therefore, using the present invention as part of the method may further include a reduction reaction to produce H. 2. The reduction reaction may utilize single-crystal tantalum nitride nanoparticles doped with at least one metal, as needed. The reduction reaction may use Ta... 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof. The reduction reaction can use Ta. 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof and at least one co-catalyst (e.g., Pt). Aqueous fluids can be water. Aqueous fluids can be water-based fluids. Aqueous fluids can be alcohols. In the method of this invention, the catalyst, such as a photocatalyst, may be a heterogeneous phase that comes into contact with a fluid or solution. This method may include, or may include, applying energy to water or an aqueous fluid in the presence of a catalyst to drive the decomposition of water molecules into hydrogen and oxygen. Energy sources include solar energy, light energy, ultraviolet light, visible light, infrared (IR) energy, and visible light irradiation. The energy source can provide at least 20 mW / cm². 2 Or at least 40 mW / cm 2 Or at least 60 mW / cm 2 Or at least 80 mW / cm 2 Or at least 100 mW / cm 2 Or at least 200 mW / cm 2 Or at least 300 mW / cm 2 or at least 400 mW / cm 2 or at least 500 mW / cm 2 or at least 600 mW / cm 2 or at least 700 mW / cm 2 or at least 800 mW / cm 2 or at least 900 mW / cm 2 or at least 1000 mW / cm 2 Illumination. The catalyst(s) may be suspended or otherwise present in water or aqueous fluids or other fluids. The catalyst(s) can adhere to a surface and come into contact with water or an aqueous fluid or other fluid. Water or an aqueous fluid or other fluid may move or remain stationary relative to the catalyst. The catalyst can be present in any amount. For example, when the catalyst is suspended in water or an aqueous fluid or other fluid, the amount can be at least 0.15 g / 150 ml of fluid or at least 0.2 g / 150 ml, or at least 0.5 g / 150 ml, or other amounts below or above any of these ranges. Similar amounts can be used when the catalyst is fixed on a surface. Although this invention and various embodiments are described herein, it was unexpectedly discovered during the development of this invention that the methods for forming Ta 3N Certain parameters and materials can significantly affect catalytic performance. Therefore, the following method is particularly superior and yields Ta 3N 5. The catalyst is particularly superior, especially as a photocatalyst. In a preferred embodiment, the Ta material used is spherical Ta metal powder, preferably with an average particle size from 25 nm to 100 nm or from about 50 nm to 100 nm. Optimal results are obtained when the average spherical particle size is less than 100 nm. Nitriding of the spherical Ta powder unexpectedly provides better Ta when nitrided at temperatures such as from 1150 K to 1230 K or from 1170 K to 1230 K, or at least 1150 K to 1160 K or at least 1170 K. 3N 5. The optimal nitriding time is at least 1 hour, or at least 2 hours, or at least 3 hours, or at least 4 hours, with 4 to 8 hours showing the best catalytic performance. A better amount of co-catalyst (i.e., CoOx) is achieved when this amount is between 0.2 wt% and 0.8 wt%, such as from 0.3 wt% to 0.7 wt%, or from 0.35 wt% to 0.5 wt%, or about 0.5 wt%. Catalytic activity practically decreases when the CoOx loading exceeds 0.5 wt%. The optimal range is 0.35 wt% to 0.5 wt%, or about 0.5 wt%. These parameters provide excellent crystallinity and low defect density, light absorption, and photocatalytic O2. 2. Catalysts released (e.g., those providing high photocatalytic O2 under visible light irradiation) 2. Release activity). In another preferred embodiment, the Ta material used is a salt-mixed Ta metal nanopowder, such as NaCl-mixed Ta metal nanopowder (e.g., NaCl cubic crystals and Ta metal nanoparticles). The salt content (such as NaCl) can be from 10 wt% to 75 wt%, such as from 25 wt% to 60 wt%, or from 35 wt% to 60 wt%, or from 40 wt% to 60 wt%, or from 50 wt% to 60 wt% to about 55 wt% (based on the total weight of Ta and salt). The presence of salt during the nitriding process unexpectedly acts as a molten salt flux during the nitriding process, promoting highly dispersed Ta. 3N Formation of 5-nanometer microparticle single crystals. The resulting Ta... 3N 5. It has monodisperse rod-shaped crystals with exposed smooth planes. Ta 3N 5. The particle size of the crystals increases with increasing nitriding temperature. Through this nitriding process, Ta... 3N 5. The presence of clear lattice fringes from the surface to the interior without grain boundaries indicates that single-crystal Ta... 3N The 5-nanometer particle system was formed using a salt (NaCl) mixture of Ta metal precursors. The preferred nitriding process conditions are actually lower compared to using spherical Ta. Here, the preferred nitriding temperature is from about 1000 K to 1100 K, such as 1050 K to 1100 K or about 1073 K. The nitriding time providing optimal properties is from 8 hours to 32 hours, with about 10 hours to 24 hours being better, and 12 hours to 18 hours, 14 hours to 17 hours, or about 16 hours being optimal. Under these preferred conditions, the prepared catalyst exhibits good performance in photocatalytic O2. 2. During the release period, the effect of irradiation wavelength on Ta 3N 5 nanometer particles release O 2. Ta exhibits the best photocatalytic performance in terms of apparent quantum yield (AQY). Unexpectedly, with the aid of salts such as NaCl as fluxes, Ta with well-defined boundaries between grain boundaries and defect states was obtained. 3N 5-nanometer microparticle single crystals. Therefore, Ta modified with CoOx co-catalyst 3N Achieving a considerably high level of photocatalytic O on 5 nanometer particles 2. Release activity. Photocatalysis O The AQY released is very high, such as at least 5%, for example from 5% to 10% (e.g., 9.4%) at 420 nm (±25 nm). These parameters provide excellent crystallinity and low defect density, light absorption and photocatalysis. 2. Catalysts released (e.g., those providing high photocatalytic O2 under visible light irradiation) 2. Release activity). Therefore, this invention relates in part to the use of suitable starting materials via thermal NH4+. 3. Nitriding produces active nano-scale single-crystal nitrides, which are used to form photocatalysts for solar energy conversion. The present invention will be further illustrated by the following embodiments, which are intended purely as examples of the present invention. Example Materials obtained. Used for Ta 3N 5. The flame-synthesized (SFE) Ta powders in the form of NaCl-free Ta metal nanoparticles (w / o NaCl / Ta) (also known as Ta nanoparticle precursors) and NaCl-mixed Ta metal nanoparticles (NaCl / Ta) (NaCl:Ta = 55:45 wt%) were supplied by Global Advanced Metals USA, Inc. Co(NO) 3) 2∙6H 2O (99.95%) as O 2. Release of the co-catalyst precursor, AgNO 3 (99.9%) as a sacrificial electron donor and La 2O 3 (99.9%) was purchased as a buffer from Kanto Chemical Corporation, FUJIFILM Wako Pure Chemical Corporation and Kojundo Chemical Laboratory Corporation, respectively. Ta 3N Synthesis of 5-nanometer particles. In the example, Ta is prepared by nitriding Ta metal nanoparticles (w / o NaCl / Ta) or NaCl mixed with Ta metal nanoparticles (NaCl / Ta). 3N 5 nanometer particles. Transfer 0.4 to 0.5 g of Ta metal nanoparticles (w / o NaCl / Ta) or 0.6 to 0.7 g of NaCl mixed with Ta metal nanoparticles (NaCl / Ta) into an alumina tube and incubate at 100 mL / min. −1 gaseous NH 3. Nitriding was performed at different temperatures for different time spans (measured at room temperature and chamber pressure). NaCl mixed with Ta metal nanopowder precursor was ground in an agate mortar for 5 min before nitriding. The nitrided sample was washed with ultrapure water at 343 K for 2 hours and then completely dried overnight at room temperature. Ta modified with CoOx cocatalyst 3N 5 nanometer particles. In the example, Ta was modified using a CoOx cocatalyst. 3N 5-nanometer microparticle photocatalyst system is formed by impregnation and subsequent NH4+. 3. Downflow heating treatment is performed. Generally speaking, Ta... 3N 5. Powder is immersed in a solution containing the required amount of Co(NO3)2. 3) The slurry was treated with strong sound and continuously stirred for 5 min to obtain Ta from an aqueous solution containing 2∙6H2O as a Co precursor. 3N 5. Powder is completely dispersed in Co(NO) 3) 2. In solution. After drying the slurry in a hot water bath, the resulting powder mixture was placed in NH4+ solution. Ta modified with CoOx was obtained by heating at 773 K for 1 hour under a gas flow of 3 (100 mL min−1). 3N 5 nm particle photocatalyst. Unless otherwise specified, in all examples, CoOx cocatalyst is supported up to 0.5 wt% of the catalyst. Materials characterization. The following analytical techniques were used. X-ray diffraction (XRD) spectra were acquired using a Rigaku MiniFlex 300 powder diffractometer equipped with Cu Kα radiation, operating at 30 kV and 30 mA. UV-vis diffuse reflectance (DRS) spectra were recorded using a spectrophotometer (V-670, JASCO) equipped with an integrating sphere, with spectral standards used as baseline correction references. Scanning electron microscopy (SEM) images were acquired using a Hitachi SU8020 system and a JEOL JSM-7600F system. High-resolution transmission electron microscopy (HRTEM) was performed using a JEOL JEM-2800 system and a JEM-2100F system. Photocatalysis O 2. Release reaction. Photocatalysis O 2. The release reaction was carried out in a Pyrex top-illuminated reaction vessel connected to a closed gas recirculation system. 0.15 g of CoOx-modified Ta was... 3N 5. Photocatalyst and 0.15 g of La 2O 3 was dispersed as a pH buffer in 150 mL of AgNO3 3. In an aqueous solution (0.2 M). The temperature was maintained at 285 K by circulating cooling water. After completely removing air from the reaction slurry by vacuuming, the suspension was irradiated with a 300 W xenon lamp equipped with a cold mirror and a cutoff filter (L42, λ≥420 nm). The reactant solution was maintained at 288 K during the reaction by a cooling water system. The released gaseous products were analyzed using an integrated thermal conductivity detector-gas chromatography system (TCD-GC) consisting of a GC-8A chromatography system (Shimadzu Corp.) equipped with a 5 Å molecular sieve column, with argon as the carrier gas. The sensitivity of the TCD was calibrated by analyzing the known amount of gas introduced into the fully vacuum reaction system containing the reaction solution under illumination. Since the deposition of Ag particles on the photocatalyst typically reduces O2... 2. Release rate, therefore, the photocatalytic O2 release rate is estimated based on the initial gas release rate. 2. Release activity. Apparent quantum yield measurement. In O Under the conditions of the release reaction, the apparent quantum yield (AQY) of the photocatalytic reaction is given by AQY(%) = [4×R] / I×100, where R and I represent the gas release rate and the incident photon flux, respectively. The coefficient 4 represents the production of one molecule of O. 2. Involving sacrificial AgNO 3 photocatalysis O 2. Four electrons are released in the reaction. The light source is a 300 W Xe lamp (MAX-303 Compact Xenon Light Source, Asahi Spectra) equipped with bandpass filters, for example, with center wavelengths of 380, 400, 420, 440, 500, 560, and 600 nm (full width at half maximum = 15 nm). The number of incident photons was measured using an LS-100 grating spectroradiometer (EKO Instruments Co., Ltd.). Example 1 Ta metal nanopowder Ta 3N 5 nanometer particles photocatalysis O 2. Release. As mentioned above, Ta 3N 5 is generally in NH 3. In the presence of gas as a nitrogen source, tantalum oxide (Ta2) is passed through at high temperature. 2O 5) The synthesis is achieved through nitridation. This reaction requires replacing three oxygen atoms with two nitrogen atoms to maintain Ta. 5+of the high oxidation state. Ta 3N The formation of 5 requires the solid anion at reducing NH 3 The slow process of diffusion in the atmosphere resulted in the reduction of Ta species and a certain amount of oxygen impurities. To avoid the problem, spherical Ta metal nanopowder (w / oNaCl / Ta) with an average particle size of about 50 to 100 nm was used as a precursor in an example of the present invention ( Figure 5 ). Due to changes in the chemical state of Ta, the nitriding of the metal Ta precursor (w / oNaCl / Ta) forms Ta 3N Phase 5 is an entirely different reaction process. Figure 1 shows the XRD patterns of the Tan nanomicroparticle precursor (w / oNaCl / Ta) and the intermediate phase of the Tan nanopowder nitrided at 773 K to 1173 K. Ta nanomicroparticle precursor (w / oNaCl / Ta) is a metallic phase (Ta 0 ). Since the nitriding temperature is generally in determining the final Ta 3N 5 plays an important role in the crystallinity and defect density of the products, so different nitriding temperatures were studied for Ta in the Ta nanopowder precursor (w / oNaCl / Ta) 3N The crystallinity, light absorption and photocatalysis of 5 nanoparticles O 2 Effects of release. As shown in Fig. 2A , XRD patterns of nitrated samples prepared at 1123 to 1223 K for 4 h with standard Ta 3N 5 Figure (Fig. 11C) is in good agreement, indicating that pure Ta was successfully obtained in this temperature range 3N 5 phases. After increasing the nitriding temperature, the intensity of the diffraction peak showed a slight change and gradually increased, meaning that the crystallinity of the sample treated at higher temperature (1173 K or 1223 K) was superior to that of the sample treated at 1123 K. According to the UV-Vis DRS ( Figure 2B ), the absorption side of these samples was located at about 600 nm with Ta 3N 5 of characteristic light absorption consistent. However, as the temperature increases, the background absorption of the sample increases, which means that more defects form as the nitriding temperature increases. Crystallization and defect levels will affect Ta 3N 5 of the photocatalytic performance, the higher the nitriding temperature, the higher the degree of crystallinity (higher the photocatalytic performance) and the higher the defect level (lower the photocatalytic performance). Ta produced at different nitrification temperatures 3N 5. Modification with CoOx co-catalyst and measurement of photocatalytic O2. 2. Release. Found Ta processed at 1173 K. 3N 5-nanometer particles exhibit the highest photocatalytic activity under visible light irradiation. 2. Release activity (Figure 2C). Although Ta treated at 1223 K... 3N 5. Ta has properties such as those processed at 1173 K. 3N While it exhibits good crystallinity, the background absorption results in Figure 2B show that it is less crystallizable than Ta treated at 1173 K. 3N 5. More defects, therefore exhibiting slightly lower activity. Besides the nitriding temperature, the nitriding period is also crucial for photocatalytic activity. Ta nanopowder precursors (w / o NaCl / Ta) were nitrided at 1173 K for 1 h to 8 h, and then modified with a CoOx cocatalyst to form Ta. 3N 5. And measure photocatalytic O 2. Release. Figure 7A shows Ta modified by CoOx co-catalyst. 3N 5 of Ta 3N 5 and O 2. XRD patterns of the release activity, in which Ta 3N The 5-series was formed by nitriding at 1173 K for 1 to 8 hours. Ta nitrided for 4 hours... 3N 5 nanometer particles have better properties than other Ta particles. 3N Sample 5 exhibited slightly stronger diffraction intensity and relatively strong photocatalytic performance. Therefore, it was determined that Ta metal nanoparticles should be used to grow Ta. 3N Optimal synthesis conditions for 5-nanometer microparticle single crystals. Considering O 2. The release of the co-catalyst will provide active catalytic sites and improve charge transfer on the surface of the photocatalyst, using Ta synthesized at 1173 K for 4 h. 3N The effect of the amount of CoOx cocatalyst on photocatalytic performance was investigated using 5 nanoparticles (Figure 8). Ta2 synthesized from Ta nanoparticle precursor (w / o NaCl / Ta) at 1173 K for 4 h was modified with the CoOx cocatalyst. 3N 5 nanometer particles. By adjusting the CoOx co-catalyst modification process, Co(NO₃)₂... 3) 2∙6H Using O₂ as a Co precursor, 0.2 wt%, 0.35 wt%, 0.5 wt%, and 0.7 wt% CoOx cocatalysts were produced. The photocatalytic O₂ content was measured. 2. Release. Activity was observed to increase with increasing CoOx loading, reaching an optimal level at a CoOx content of 0.5 wt%, and then decreasing with further increases in CoOx content. Ta nitrided at 1173 K for 4 h was observed by SEM and HRTEM. 3N Detailed morphological information of 5-nanometer particles. As shown in Figures 2D and 2E, Ta 3N Five samples exhibited irregular crystal forms with a particle size of less than 100 nm. Small crystal size is beneficial to photocatalytic performance because the shortened migration distance of electrons and holes to the surface of the photocatalyst greatly reduces the chance of charge recombination. From the magnified images of the red and blue square areas in Figure 2E (indicated by the arrows in Figure 2E), Ta was observed... 3N The clear diffraction patterns within the 5-nanometer particles and the distinct grain boundaries between them confirm that Ta 3N The 5-nanometer particle system has a certain degree of aggregation and good crystallization of single crystals. Example 2 The initial composition of NaCl / Ta metal nanoparticles (NaCl / Ta) consisted of NaCl cubic crystals and Ta metal nanoparticles (Figure 9). 3N Photocatalysis of O on 5 nanometer particles 2. Release. When NaCl is mixed with Ta metal nanoparticles in NH4+... Pure Ta was obtained by nitriding at 1023 K, 1073 K, 1123 K and 1173 K for 16 h. 3N 5 phases and Ta 3N The crystallinity of 5 increases with increasing temperature (Figure 3A). Figure 3C shows the crystallinity of Ta in NaCl mixed with Ta metal nanoparticles (NaCl / Ta). 3N SEM image of 5-nanometer particles. NaCl at a concentration of 55 wt% in the mixture acts as a molten salt flux during nitriding to promote highly dispersed Ta. 3N 5-nanometer microparticle single crystal formation. Due to the action of NaCl flux, the obtained Ta... 3N 5-nanometer particles are monodisperse rod-shaped crystals with exposed smooth planes. 3N 5. The particle size of the crystals increases with increasing nitriding temperature, which is consistent with the increase in intensity of the XRD pattern (Figure 3A). Ta metal nanopowder mixed with NaCl... 3N HRTEM images of 5-nanometer particles show clear lattice striations from the surface to the interior without grain boundaries, indicating that single-crystal Ta 3N The 5-nanometer particle system was formed using NaCl mixed with Ta metal precursor (NaCl / Ta) (Figure 3D). Ta prepared from NaCl mixed with Ta metal nanoparticles (NaCl / Ta) 3N 5-nanometer microcrystalline particles were modified with a CoOx cocatalyst and the photocatalytic O2 content was measured. 2. Release. Ta with Ta metal precursor (w / o NaCl / Ta) 3N Compared to 5 nanometer particles (Figure 2C), highly dispersed Ta prepared from NaCl mixed with Ta metal nanoparticles (NaCl / Ta) exhibits superior dispersion. 3N 5-nanometer microparticle single crystals (NaCl / Ta) using AgNO 3 exhibits stronger photocatalytic activity as a hole-sacrificing reagent. 2. Release performance (Figure 3B). Ta from NaCl-mixed Ta metal nanoparticles (NaCl / Ta) nitrided at 1073 K. 3N 5 nanometer particles photocatalysis O 2. The release activity was the highest among other samples at different temperatures (Figure 3B). Besides the nitriding temperature, the nitriding period was also found to be crucial for photocatalytic activity. NaCl mixed with Ta metal nanoparticles (NaCl / Ta) was nitrided at 1073 K for 8 to 32 h to form Ta. 3N 5. Then, the material was modified with a CoOx co-catalyst and the photocatalytic O2 was measured. 2. Release (Figures 10A to C). As the nitridation time increased from 8 h to 16 h, Ta... 3N The increased crystallinity and particle size of 5 nanometer particles lead to photocatalytic O 2. Increased release. Further extending the nitridation time gradually reduces Ta. 3N 5 particles of O The release of activity is likely due to the increased charge migration distance and reduced surface area in large particles. Monodisperse single-crystal Ta was synthesized from NaCl mixed with Ta nanoparticles (NaCl / Ta) at 1073 K for 16 h. 3N 5-nanometer particles exhibit optimal photocatalytic O 2. Release performance. Figure 4 shows the photocatalytic O2 release performance. 2. During the release period, Ta 3N The apparent quantum yield (AQY) of 5 nm particles is dependent on the irradiation wavelength. AQY increases at wavelengths less than 400 nm, peaks at 400 nm, and then gradually decreases to a minimum at wavelengths between 420 nm and 600 nm, compared with Ta nanoparticles prepared from NaCl mixed with Ta nanoparticles (NaCl / Ta). 3N The absorption curves of the 5 nm particles show good agreement. The AQY values ​​are 9.4% at 420 nm (±25 nm) and 5.4% at 500 nm (±25 nm), which is satisfactory for Ta prepared solely from the precursor without surface or volume modification. 3N 5. The photocatalyst system exhibits relatively high efficiency. This confirms that the metal Ta nanoparticle system is free of defect states and grain boundaries, enabling highly efficient photocatalytic O2. 2. Release of high-quality Ta 3N Promising material for 5-nanometer microparticle photocatalysts. In summary, as the examples show, single-crystal Ta 3N 5 nanometer particle systems are made from metallic Ta nanoparticles or a mixture of NaCl and Ta nanoparticle precursors via NH4+. Preparation via oxidation process in nitriding. Ta metal to Ta 3N The rapid conversion of the five phases results in high-quality Ta 3N 5-nanometer particles were formed under relatively mild nitriding conditions. Furthermore, with the aid of NaCl as a flux, Ta particles with clearly defined boundaries and no grain boundaries or defect states were obtained. 3N 5-nanometer microparticle single crystals. Therefore, Ta modified with CoOx co-catalyst 3N Achieving a considerably high level of photocatalytic O on 5 nanometer particles 2. Release activity. Photocatalysis O The released AQY was as high as 9.4% at 420 nm (±25 nm). This study confirms that the use of appropriate starting materials and thermal NH4+ release... 3. The effectiveness of nitriding in producing active nano-sized single-crystal nitrides, which is useful for forming photocatalyst systems for solar energy conversion. This invention comprises, in any order and / or in any combination, the following forms / embodiments / features: 1. This invention comprises MO-based... x Single-crystal Ta modified by co-catalyst 3N 5 nanometer particles, including MOx-based metal oxides, M-based metals, and O x This indicates that it is an oxide that is part of the metal oxide. 2. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein MOx-based CoO x Co-catalyst, wherein O x This indicates an oxide that is part of cobalt oxide. 3. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the MOx cocatalyst is based on single-crystal Ta 3N At least 0.01 wt% of the total weight of 5 nanometer particles was impregnated into the Ta 3N 5 nanometer particles. 4. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the MOx cocatalyst is based on single-crystal Ta 3N At least 0.5 wt% of the total weight of 5 nanometer particles were impregnated into the Ta. 3N 5 nanometer particles. 5. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the MOx cocatalyst is CoO, Co 2O, Co 2O 3 and / or Co 3O 4. 6. Single-crystal Ta as in any previous or subsequent embodiments / features / states 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles have a photocatalytic O content of more than 0.1%. 2. Apparent quantum yield of the release reaction (OER). 7. Single-crystal Ta as in any previous or subsequent examples / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles have a photocatalytic O content ranging from 0.1% to 9.4%. 2. Apparent quantum yield of the release reaction (OER). 8. Single-crystal Ta as in any previous or subsequent embodiment / feature / state. 3N 5. Nanoparticles or methods or other embodiments, wherein such single-crystal nanoparticles are also doped with at least one metal. 9. A catalyst (or a method of using the catalyst) comprising single-crystal nanoparticles or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles, and platinum and / or other metal catalysts distributed on the surface of such single-crystal nanoparticles. 10. A photocatalyst (or a method of using the catalyst), comprising single-crystal nanoparticles or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles with a solar-to-hydrogen (STH) energy conversion efficiency exceeding 0.015%. 11. Photocatalysts or single-crystal Ta as described in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the solar-to-hydrogen (STH) energy conversion efficiency is from 0.015% to 0.1%. 12. Photocatalysts or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, comprising any single-crystal nanoparticles of any previous or subsequent embodiments / features / states, and having an H+ concentration exceeding 5 μmol / h. 2. Yield. 13. Photocatalysts or single-crystal Ta as in any previous or subsequent examples / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the H 2. Yields ranged from 5 µmol / h to 13 µmol / h. 14. Photocatalysts or single-crystal Ta as described in any previous or subsequent examples / characteristics / states. 3N 5 nanometer particles or methods or other embodiments, and having an apparent quantum yield (AQY) exceeding 0.15%. 15. Photocatalysts or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein the AQY is from 0.15% to 0.54%. 16. Photocatalysts or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, further having H+ exceeding 5 μmol / h 2. Yield or apparent quantum yield (AQY) exceeding 0.15%, or both. 17. A photocatalyst (or a method of using the catalyst) comprising single-crystal Ta as described in any previous or subsequent embodiments / characteristics / states. 3N 5 nanometer particles or other embodiments. 18. A water splitting method comprising using a photocatalyst or single-crystal Ta from any previous or subsequent embodiment / feature / state. 3N 5 nanometer particles are present in a fluid or solution along with energy. 19. A method for the catalytic splitting of water into hydrogen and oxygen, wherein an oxidation reaction produces O₂. 2. Contains a photocatalyst or single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles are present in a fluid or solution along with an energy source. 20. As in any previous or subsequent embodiments / features / states, the method (or catalyst or nanoparticles) further includes a reduction reaction to produce H₂. 2. 21. The method (or catalyst or nanoparticles) of any prior or subsequent embodiment / feature / state, wherein the reduction reaction uses tantalum nitride single-crystal nanoparticles doped with at least one metal. 22. The method (or catalyst or nanoparticles) of any prior or subsequent embodiment / feature / state, wherein the reduction reaction uses Ta 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof. 23. The method (or catalyst or nanoparticles) of any previous or subsequent embodiment / characteristic / state, wherein the reduction reaction uses Ta. 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Single-crystal nanoparticles of Zr or any combination thereof and at least one co-catalyst. 24. A method for manufacturing single-crystal nanoparticles of any prior or subsequent embodiment / feature / state, the method comprising a nitriding process of spherical tantalum powder or tantalum aggregates containing salt or flame-synthesized tantalum with salt encapsulation as desired, wherein the nitriding process includes NH4+. 3. Nitriding is carried out at 700 K or higher for 10 minutes to 32 hours to form tantalum nitride, followed by impregnation of tantalum nitride with a MOx co-catalyst. 25. The method (or catalyst or nanoparticles) as in any previous or subsequent examples / features / states, wherein the temperature is 700 K to 1200 K for 1 hour to 8 hours. 26. The method (or catalyst or nanoparticles) as in any previous or subsequent examples / features / states, further comprising using MgCl₂. 2 or other first metal salts and ZrOCl 2. Tantalum nitride impregnated with 2 or other second metal salts. 27. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles or methods or other embodiments, wherein the single-crystal nanoparticles are monodisperse nanorod particles. 28. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles or methods or other embodiments, wherein the monodisperse nanorod particles have an average length of 50 nm to 500 nm. 29. A method (or catalyst or nanoparticle) as in any previous or subsequent embodiment / feature / state, wherein the photocatalyst is a heterogeneous phase in contact with a fluid or solution. 30. Single-crystal Ta as in any previous or subsequent embodiment / feature / state. 3N 5 nanometer particles or methods or other embodiments, wherein the energy source is solar energy. 31. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles provide at least 200 O 2 Release rate / umol h -1 32. Single-crystal Ta as in any previous or subsequent embodiments / features / states 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles provide at least 300 O 2 Release rate / umol h -1 33. Single-crystal Ta as in any previous or subsequent embodiments / features / states 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles provide at least 450 O 2 Release rate / umol h -1 34. Single-crystal Ta as in any previous or subsequent embodiments / features / states 3N 5. Nanoparticles or methods or other embodiments, the method comprising subjecting spherical tantalum powder having an average particle size of 20 nm to 100 nm to the nitriding process at a temperature of 1150 K to 1230 K for 4 to 8 hours, and impregnating the tantalum nitride with a MOx co-catalyst loaded with 0.3 wt% to 0.7 wt%. 35. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, the method comprising subjecting the tantalum aggregates containing the salt aggregates or the flame-synthesized tantalum encapsulated with the salt to the nitriding process at a temperature of 1000 K to 1100 K for 8 to 32 hours, and impregnating the tantalum nitride with a MOx cocatalyst loaded with 0.3 wt% to 0.7 wt%. 36. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles or methods or other embodiments, wherein the tantalum aggregates containing the salt aggregates or the flame-synthesized tantalum encapsulated with the salt have a salt content of 25 wt% to 70 wt% based on the weight of tantalum and salt. 37. Methods (or catalysts or nanoparticles) as in any previous or subsequent embodiments / features / states, wherein the impregnation includes the Ta 3N 5 nanoparticles are mixed with a metal precursor (such as a Co precursor) to form a dispersion slurry, and then the modified nanoparticles are recovered and dried, and then subjected to oxidation at 500 K or higher in NH4+. The nanoparticles were heated under an airflow to obtain Ta-modified by MOx cocatalyst. 3N 5 nanometer particles. 38. Ta prepared by any previous or subsequent example / characteristic / state method (or catalyst or nanoparticles) modified with MOx co-catalyst. 3N 5 nanometer particles. 39. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles or methods or other embodiments, wherein such single-crystal nanoparticles are also doped with at least two metals. 40. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5. Nanoparticles or methods or other embodiments, wherein such single-crystal nanoparticles are also co-doped with two metals. 41. Single-crystal Ta as in any previous or subsequent embodiments / features / states. 3N 5 nanometer particles or methods or other embodiments, wherein such single-crystal nanometer particles are also doped to form Ta 3N 5:Mg+Zr or Ta 3N 5: Mg or Ta 3N 5: Zr or any combination thereof. 42. A catalyst comprising a) modified by a MOx co-catalyst, wherein O x This indicates that it is a part of the oxide of cobalt oxide and 2) single crystal Ta modified or doped by Zr and / or Mg. 3N 5 nanometer particles. 43. A method for catalytically splitting water into hydrogen and oxygen, the method comprising using a catalyst or single-crystal Ta as in any previous or subsequent embodiments / characteristics / states. 3N 5 nanometer particles or methods or other embodiments. This invention may include any combination of the various features or embodiments described above and / or below as set forth in sentences and / or paragraphs. Any combination of features disclosed herein is considered part of this invention and is not intended to limit the composable features. The invention herein refers to certain examples shown, and it should be understood that these examples are presented by way of example and not by way of limitation. Although exemplary examples are discussed, the foregoing detailed description is intended to be construed as covering all modifications, substitutions, and equivalents that may fall within the spirit and scope of the invention as defined in other inventive descriptions. All references cited in this invention are incorporated herein by reference in their entirety, provided they do not contradict this invention. This invention may include any combination of the various features or embodiments described in the sentences and / or paragraphs above and / or below the claims. Any combination of features disclosed herein is considered part of this invention and is not intended to limit the combinable features. Other embodiments of the invention will become apparent to those skilled in the art from consideration of this specification and the practice of the invention disclosed herein. This specification and examples are intended to be illustrative only, and the true scope and spirit of the invention are defined by the following claims and their equivalents. Figure 1 shows (a) the Ta nanoparticle precursor (w / o NaCl / Ta) used in one example of this application, and the products produced by nitriding at (b) 773 K, (c) 923 K, (d) 1023 K, (e) 1073 K, (f) 1123 K and (g) 1173 K for 10 min, and (h) the Ta obtained from Ta nanoparticle powder (w / o NaCl / Ta) nitrided at 1173 K for 4 h. 3N XRD pattern of 5. Figure 2A shows Ta produced by nitriding at different temperatures for 4 h using Ta nanoparticles (w / o NaCl / Ta). 3N XRD pattern obtained from 5 nanometer particles. Figure 2B shows Ta produced by nitriding at different temperatures for 4 h using Ta nanoparticles (w / o NaCl / Ta). 3N UV-Vis DRS data obtained from 5-nanometer particles. Figure 2C shows the effect of the nitriding temperature of the catalyst of the present invention on O. 2. Bar graph of release rate. This Ta 3N Photocatalysis of O on 5 nanometer particles 2. Release. Conditions: Catalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 2D shows Ta nanoparticles fabricated by nitriding Ta nanoparticles (w / o NaCl / Ta) at 1173 K for 4 h. 3N SEM image of 5-nanometer particles. Figure 2E shows Ta nanoparticles prepared by nitriding Ta nanoparticles (w / o NaCl / Ta) at 1173 K for 4 h. 3N HRTEM and SAED images of 5-nanometer particles. Figure 3A shows the XRD patterns, and Figure 3B shows the Ta nanoparticles prepared by mixing NaCl with Ta nanoparticles (NaCl / Ta) at different temperatures for 16 h. 3N 5 nanometer particles photocatalysis O 2. Bar graph of release activity. Conditions: catalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 3C is a SEM image of these nanoparticles from Figure 3A. Figure 3D shows Ta nanoparticles prepared by mixing NaCl with Ta nanoparticles (NaCl / Ta) at 1073 K for 16 h. 3N HRTEM image of 5-nanometer particles. Figure 4 shows the wavelength versus AQY: in photocatalysis O 2. Ta produced by nitriding NaCl mixed with Ta nanoparticles (NaCl / Ta) at 1073 K for 16 h as a function of the incident light wavelength during the release period. 3N Apparent quantum yield of 5 nanometer particles. Conditions: catalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3 buffer solution, 0.15 g; light source, 300 W xenon lamp equipped with multiple bandpass filters. Figure 5 shows the formation of Ta by nitriding in one embodiment of the present invention. 3N SEM image of Ta metal nanoparticles (w / o NaCl / Ta). Figure 6 shows the effect of irradiation time on O 2. Release Graph: Ta released using Ta nanoparticles (w / o NaCl / Ta) nitrided at different temperatures for 4 hours. 3N Photocatalysis of O on 5 nanometer particles 2. Release time process. Conditions: Catalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 7A shows the XRD patterns of the O series, and Figure 7B shows the effect of nitriding time on O. 2. Release rate, particularly Ta released from Ta nitride nanoparticles (w / o NaCl / Ta) at 1173 K for different time spans. 3N 5 nanometer particles photocatalysis O 2. Release activity diagram. Conditions: Photocatalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 8 shows the relationship between CoOx loading and O 2. Release rate graph. Figure 8 shows the specific release rate of CoO. x The co-catalyst supported pair used Ta nanoparticles synthesized from Ta nanoparticles (w / o NaCl / Ta) at 1173 K for 4 h. 3N The effect of 5-nanometer particles on photocatalytic performance. Conditions: photocatalyst, 0.15 g; 0.2 M AgNO3. 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 9 is a SEM image of NaCl mixed with Ta metal nanopowder (NaCl / Ta) used in one embodiment of the present invention. Figure 10A shows the catalyst of the present invention, namely, Ta obtained by nitriding NaCl mixed with Ta nanoparticles (NaCl / Ta) at 1073 K for different time spans. 3N The effect of nitriding temperature of 5 nanometer particles on O 2. Bar graph of release rate: Ta released from NaCl-mixed Ta nanoparticles (NaCl / Ta) nitrided at 1073 K for different time spans. 3N 5 nanometer particles photocatalysis O 2. Release activity. Conditions: Photocatalyst, 0.15 g; CoO x Loading, 0.5 wt%; 0.2 M AgNO3 3 aqueous solution, 150 mL; La 2O 3. Buffer solution, 0.15 g; light source, 300 W xenon lamp (λ ≥ 420 nm). Figure 10B is the XRD pattern of the catalyst tested in Figure 10A. Figure 10C shows the Ta nanoparticles obtained from NaCl-mixed Ta nanoparticles (NaCl / Ta) nitrided at 1073 K for different time spans, as tested in Figure 10A. 3N SEM image of 5-nanometer particles. Figure 11A to C series TaN 0.1 (Figure 11A), TaN (Figure 11B) and Ta 3N 5. Standard XRD pattern (Figure 11C).

Claims

1. A single-crystal Ta3N5 nanoparticle modified by MOx cocatalyst, wherein MOx is a metal oxide, specifically CoOx, and Ox represents an oxide that is a portion of the cobalt oxide.

2. The single-crystal nanoparticles of claim 1, wherein the MOx cocatalyst is impregnated onto the Ta3N5 nanoparticles in an amount of 0.2 wt% to 0.8 wt% based on the total weight of the single-crystal Ta3N5 nanoparticles.

3. The single-crystal nanoparticles of claim 1, wherein the MOx cocatalyst is impregnated onto the Ta3N5 nanoparticles in an amount of 0.5 wt% to 0.8 wt% based on the total weight of the single-crystal Ta3N5 nanoparticles.

4. The single-crystal nanoparticles of claim 1, wherein the MOx cocatalyst is CoO, Co2O, Co2O3 and / or Co3O4.

5. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles have an apparent quantum yield of more than 0.1% for photocatalytic O2 release reaction (OER).

6. The single-crystal nanoparticles of claim 1, wherein the single-crystal nanoparticles have an apparent quantum yield of photocatalytic O2 release reaction (OER) of 0.1% to 9.4%.

7. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles are also doped with at least one metal.

8. A catalyst comprising single-crystal nanoparticles as claimed in claim 1 and platinum and / or other metal catalysts distributed on the surface of the single-crystal nanoparticles.

9. A photocatalyst comprising single-crystal nanoparticles as claimed in claim 1 and having a solar-to-hydrogen (STH) energy conversion efficiency of more than 0.015%.

10. The photocatalyst of claim 9, wherein the solar-to-hydrogen (STH) energy conversion efficiency is from 0.015% to 0.1%.

11. A photocatalyst comprising single-crystal nanoparticles as claimed in claim 1 and having an H2 yield of more than 5 μmol / h.

12. The photocatalyst of claim 11, wherein the H2 yield is from 5 µmol / h to 13 µmol / h.

13. A photocatalyst comprising single-crystal nanoparticles as claimed in claim 1 and having an apparent quantum yield (AQY) of more than 0.15%.

14. The photocatalyst of claim 13, wherein the AQY is from 0.15% to 0.54%.

15. The photocatalyst of claim 9 further having an H2 yield of more than 5 μmol / h or an apparent quantum yield (AQY) of more than 0.15%, or both.

16. A photocatalyst comprising single-crystal nanoparticles as claimed in claim 1.

17. A water splitting method comprising using a photocatalyst as claimed in claim 16 together with energy in a fluid or solution.

18. A method for catalytically splitting water into hydrogen and oxygen, wherein the oxidation reaction to produce O2 comprises using a photocatalyst as claimed in claim 16.

19. The method of claim 18, further comprising a reduction reaction to produce H2.

20. The method of claim 19, wherein the reduction reaction uses tantalum nitride single-crystal nanoparticles doped with at least one metal.

21. The method of claim 19, wherein the reduction reaction uses single-crystal nanoparticles of Ta3N5:Mg+Zr or Ta3N5:Mg or Ta3N5:Zr or any combination thereof.

22. The method of claim 19, wherein the reduction reaction uses single-crystal nanoparticles of Ta3N5:Mg+Zr or Ta3N5:Mg or Ta3N5:Zr or any combination thereof, and at least one co-catalyst.

23. A method for preparing single-crystal nanoparticles as claimed in claim 1, the method comprising a nitriding process of spherical tantalum powder or tantalum aggregates containing salt or flame-synthesized tantalum encapsulated with salt as needed, wherein the nitriding process comprises nitriding at a temperature of 700 K or higher under an NH3 flow for 10 minutes to 32 hours to form tantalum nitride and then impregnating the tantalum nitride with a MOx cocatalyst.

24. The method of claim 23, wherein the temperature is 700 K to 1200 K for 1 hour to 8 hours.

25. The method of claim 23, further comprising impregnating tantalum nitride with MgCl2 or other first metal salt and ZrOCl2 or other second metal salt.

26. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles are monodisperse nanorod particles.

27. The single-crystal nanoparticles of claim 26, wherein the monodisperse nanorod particles have an average length of 50 nm to 500 nm.

28. The method of claim 17, wherein the photocatalyst is a heterogeneous phase in contact with the fluid or the solution.

29. The method of claim 28, wherein the energy source is solar energy.

30. The single-crystal nanoparticles of claim 1, wherein the single-crystal nanoparticles provide an O2 release rate of at least 200 / umol h-1.

31. The single-crystal nanoparticles of claim 1, wherein the single-crystal nanoparticles provide an O2 release rate of at least 300 / umol h-1.

32. The single-crystal nanoparticles of claim 1, wherein the single-crystal nanoparticles provide an O2 release rate of at least 450 / umol h-1.

33. The method of claim 23, comprising subjecting the spherical tantalum powder having an average particle size of 20 nm to 100 nm to the nitriding process at a temperature of 1150 K to 1230 K for 4 to 8 hours, and impregnating tantalum nitride with a MOx cocatalyst with a loading of 0.3 wt% to 0.7 wt%.

34. The method of claim 23, comprising subjecting the tantalum aggregate containing the salt aggregate or the flame-synthesized tantalum encapsulated with the salt to the nitriding process at a temperature of 1000 K to 1100 K for 8 to 32 hours, and impregnating tantalum nitride with a MOx cocatalyst with a loading of 0.3 wt% to 0.7 wt%.

35. The method of claim 34, wherein the tantalum aggregate containing the salt aggregate or the flame-synthesized tantalum encapsulated with the salt has a salt content of 25 wt% to 70 wt% based on the weight of tantalum and salt.

36. The method of any one of claims 33 to 35, wherein the impregnation comprises mixing the Ta3N5 nanoparticles with a metal precursor to form a dispersion slurry and then recovering and drying the recovered modified nanoparticles and then heating the nanoparticles at a temperature of 500 K or higher under an NH3 gas stream to obtain MOx co-catalyst modified Ta3N5 nanoparticles.

37. A Ta3N5 nanoparticle modified by a MOx cocatalyst, prepared by the method of any one of claims 23 and 33 to 36.

38. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles are also doped with at least two metals.

39. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles are also co-doped with two metals.

40. The single-crystal nanoparticles of claim 1, wherein such single-crystal nanoparticles are also doped to form Ta3N5:Mg+Zr or Ta3N5:Mg or Ta3N5:Zr or any combination thereof.

41. A catalyst comprising single-crystal Ta3N5 nanoparticles, wherein a) it is modified by a MOx co-catalyst, wherein MOx is a metal oxide, which is CoOx, wherein Ox represents an oxide that is a portion of cobalt oxide and b) it is modified or doped by Zr and / or Mg.

42. A method for catalytically splitting water into hydrogen and oxygen, the method comprising using a catalyst as claimed in claim 41.

Images