A Se1 / NiO pseudometallic single-atom material, its preparation method and application

Abstract

The application provides a Se1 / NiO pseudo-metallic monatomic material and a preparation method and application thereof. The application provides a preparation method of the Se1 / NiO pseudo-metallic monatomic material, which comprises the following steps: A) mixing nickel sulfate, water and potassium persulfate to obtain a solution A; B) adding ammonia water to the solution A to adjust the pH value, and after the reaction is completed, performing solid-liquid separation, washing and drying to obtain nickel hydroxide; C) placing the nickel hydroxide and selenium powder as a matrix and a nonmetal source precursor respectively in a tube furnace, and under a protective atmosphere, heating to 300-350 DEG C to react to obtain the Se1 / NiO pseudo-metallic monatomic material. The Se1 / NiO pseudo-metallic monatomic material provided by the application can be used as an OER electrocatalyst, breaks through the theoretical overpotential limit of an adsorption evolution mechanism in an OER process, and exhibits excellent electrochemical stability.

Description

Technical Field

[0001] This invention relates to the field of novel functional material creation and application design, and particularly to a Se1 / NiO pseudometal single-atom material, its preparation method, and its application. Background Technology

[0002] With the deepening of the new round of technological and industrial revolution, the foundational role of materials in supporting strategic emerging industries is becoming increasingly apparent, and the creation of new energy materials is a major way for materials research to directly serve the national energy strategy. Single-atom catalysts have attracted attention due to their unique electronic structure and maximum atom utilization efficiency. However, due to the complex synthesis process required, ordinary metal-based single-atom catalysts are difficult to design, have cumbersome preparation processes, are prone to poisoning, and face problems such as low product selectivity. The differences between non-metallic elements and metallic elements in terms of charge, electronegativity, valence electron distribution, and even their positions in compounds will give rise to unique coordination modes and structural characteristics. Under external field excitation, they will inevitably exhibit physicochemical properties and electronic states different from those of metallic single atoms, resulting in superior apparent performance. However, current research on non-metallic single-atom materials is still relatively limited. Therefore, novel non-metallic single-atom functional materials created based on non-metallic elements have the advantages of low cost, simple synthesis methods, effective substrate utilization, and environmental friendliness, and are expected to become the next generation of materials stars. The fine control of their structure will provide a new research platform for the explanation of strongly correlated systems and for research in physics, chemistry, and materials science.

[0003] Rapidly developing societies place higher demands on energy. Electrocatalytic oxidation-reduction (OER) reactions, as fundamental reactions, participate in a series of energy conversion and storage processes, including green hydrogen production, CO2 reduction, and hydrogen-oxygen fuel cells. However, due to the high thermodynamic potential energy and stringent reaction kinetics, current electrocatalysts are still some distance from practically efficient applications. Therefore, actively exploring and preparing highly efficient OER electrocatalysts is particularly important.

[0004] In-depth research into the atomic and electronic structures of single-atom materials and the establishment of unified guiding principles for synthesis are of significant practical importance for the precise control of their synthesis and the expansion of their practical applications. However, the fine control of material energy level structures is inevitably affected by crystal structure, electrons, and electron spin, which adds obstacles to the control of electronic states and covalent properties. Metal single-atom catalysts have been widely used in OER catalytic performance testing and have shown certain application potential. However, non-metallic single-atom catalysts have often been neglected due to dissolution or oxidation, and they are extremely prone to bonding with metal components to form new compound phases, making them difficult to prepare in a controllable manner. Therefore, it is urgent to develop new synthetic methods for the quantitative preparation of non-metallic single-atom materials. Summary of the Invention

[0005] In view of this, the present invention provides a Se1 / NiO pseudometal single-atom material, its preparation method, and its application. The Se1 / NiO pseudometal single-atom material provided by the present invention can be used as an OER electrocatalyst, breaking through the theoretical limit overpotential of the adsorption evolution mechanism in the OER process, and exhibiting excellent electrochemical stability.

[0006] This invention provides a method for preparing Se1 / NiO pseudometal single-atom materials, comprising the following steps:

[0007] A) Mix nickel sulfate, water, and potassium persulfate to obtain solution A;

[0008] B) Add ammonia to solution A to adjust the pH value. After the reaction is complete, separate the solid and liquid, wash and dry to obtain nickel hydroxide.

[0009] C) The nickel hydroxide and selenium powder, as the matrix and non-metallic source precursor, are placed in a tube furnace and reacted at 300-350°C under a protective atmosphere to obtain Se1 / NiO pseudometal single-atom material.

[0010] Preferably, in step C), the mass ratio of nickel hydroxide to selenium powder is (30-60) mg:(0.8-1.2) g.

[0011] Preferably, in step C), the inlet rate of the protective gas providing the protective atmosphere is 200-250 mL / min.

[0012] Preferably, in step C), the heating rate is 5 to 10 °C / min.

[0013] Preferably, step C) specifically includes:

[0014] Nickel hydroxide is placed in a ceramic boat 1, selenium powder is placed in a ceramic boat 2, and the ceramic boats 1 and 2 are placed in a quartz tube, with the ceramic boat 1 located in the middle of the quartz tube and the ceramic boat 2 located upstream of the ceramic boat 1. A protective gas is introduced to purge the quartz tube, and the temperature is raised to 300-350℃ to react, thus obtaining Se1 / NiO pseudometal single-atom material.

[0015] Preferably, the distance between the porcelain boat 1 and the porcelain boat 2 is 10-20cm.

[0016] Preferably, in step A), the mass ratio of nickel sulfate to potassium persulfate is (10-15):3.

[0017] Preferably, the ratio of ammonia in step B) to nickel sulfate in step A) is (5-15) mL : (10-15) g.

[0018] The present invention also provides a Se1 / NiO pseudometal single-atom material prepared by the preparation method described in the above technical solution.

[0019] The present invention also provides an application of the Se1 / NiO pseudometal single-atom material described in the above technical solution as a catalyst in electrocatalytic oxygen evolution.

[0020] This invention provides a method for preparing Se1 / NiO pseudometallic single-atom materials, comprising the following steps: A) mixing nickel sulfate, water, and potassium persulfate to obtain solution A; B) adding ammonia to solution A to adjust the pH value, and after the reaction is complete, separating the solid and liquid, washing, and drying to obtain nickel hydroxide; C) placing the nickel hydroxide and selenium powder as a matrix and non-metallic source precursor in a tube furnace, and reacting at 300-350℃ under a protective atmosphere to obtain Se1 / NiO pseudometallic single-atom materials. The Se1 / NiO pseudometallic single-atom materials prepared by this invention exhibit unique elemental properties and coordination modes, especially the modulated energy level structure and electronic states, which show catalytic activity and stability different from the physicochemical properties of common metallic single atoms or compounds doped with conventional non-metallic elements. Experimental results show that under alkaline conditions, the powdered Se1 / NiO non-metallic single-atom material can reach 10 mA / cm² at an overpotential of 265 mV. 2 And at 20mA / cm 2 It continuously electrolyzes water to produce oxygen for more than 25 hours at a current density, demonstrating extremely high intrinsic catalytic activity. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 The X-ray diffraction pattern of the Se1 / NiO pseudometal single-atom material obtained in Example 1;

[0023] Figure 2 The image shows a scanning electron microscope (SEM) image (EDS) of the Se1 / NiO pseudometallic single-atom material obtained in Example 1; wherein, Figure 2 (a) is a SEM image. Figure 2 (b) is the EDS plot;

[0024] Figure 3 This is a high-angle annular dark-field image-scanning transmission electron microscope image of the Se1 / NiO pseudometal single-atom material obtained in Example 1;

[0025] Figure 4 This is a diagram showing the K-edge X-ray absorption extension of Se in R space for the Se1 / NiO pseudometallic single-atom material obtained in Example 1.

[0026] Figure 5 This is the XPS image of the prepared Se1 / NiO sample;

[0027] Figure 6 This is the Ni L-edge synchrotron resonance inelastic X-ray scattering pattern of the prepared Se1 / NiO;

[0028] Figure 7 The graphs show the performance of the samples obtained in the examples and comparative examples under alkaline conditions for electrocatalytic oxygen evolution.

[0029] Figure 8 The image shows the MH curve of the Se1 / NiO pseudometal single-atom material obtained in Example 1. Detailed Implementation

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0032] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0033] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0034] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 300~350℃ means that the units for the left endpoint "300" and the right endpoint "350" are both in degrees Celsius.

[0035] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0036] This invention provides a method for preparing Se1 / NiO pseudometal single-atom materials, comprising the following steps:

[0037] A) Mix nickel sulfate, water, and potassium persulfate to obtain solution A;

[0038] B) Add ammonia to solution A to adjust the pH value. After the reaction is complete, separate the solid and liquid, wash and dry to obtain nickel hydroxide.

[0039] C) The nickel hydroxide and selenium powder, as the matrix and non-metallic source precursor, are placed in a tube furnace and reacted at 300-350°C under a protective atmosphere to obtain Se1 / NiO pseudometal single-atom material.

[0040] This invention develops an energy-saving, rapid solid-phase thermal diffusion method for the controllable preparation of non-metallic single-atom materials. It creates a novel Se1 / NiO pseudometallic single-atom structure where non-metallic elements occupy metallic sites, and provides a new method for controlling energy level structure and electronic states. This enables highly efficient OER catalytic reaction processes and demonstrates potential applications in materials, physics, chemistry, and energy catalytic conversion. In this paper, the subscript 1 in Se1 / NiO does not represent the elemental ratio, but rather indicates that it (Se in this paper) is a single-atom structure, a conventional notation for single-atom materials. In this invention, the new Se1 / NiO material is characterized by non-metallic elements occupying the original metallic positions, dispersed at the atomic level; therefore, it is called a pseudometallic single-atom.

[0041] Regarding step A) :

[0042] A) Mix nickel sulfate, water and potassium persulfate to obtain solution A.

[0043] In this invention, the water is preferably deionized water. The preferred ratio of nickel sulfate to water is (10-15) g : (60-120) mL. The preferred mass ratio of nickel sulfate to potassium persulfate is (10-15) : 3, specifically 10 : 3, 11 : 3, 12 : 3, 13 : 3, 14 : 3, or 15 : 3.

[0044] In this invention, there are no particular restrictions on the method of mixing nickel sulfate, water, and potassium persulfate; any conventional mixing method in the art, such as stirring or ultrasonication, is sufficient to mix the materials. Specifically, in this invention, nickel sulfate is dissolved in water, stirred until dissolved, and then potassium persulfate is added and the mixture is stirred and mixed again to obtain solution A.

[0045] Regarding step B) :

[0046] B) Add ammonia to solution A to adjust the pH value. After the reaction is complete, separate the solid and liquid, wash and dry to obtain nickel hydroxide.

[0047] In this invention, the concentration of the ammonia water is not particularly limited, and industrial ammonia water (i.e., an aqueous solution containing 25% to 28% ammonia) is acceptable. In this invention, the preferred ratio of the ammonia water to nickel sulfate in step A) is (5 to 15) mL: (10 to 15) g.

[0048] In this invention, after adding ammonia to adjust the pH value, the reaction is allowed to proceed for a certain period of time until complete. The reaction is preferably carried out under stirring conditions; that is, after adding ammonia to adjust the pH value, the reaction is stirred until complete. In this invention, there are no special temperature restrictions for the above operations; they can be carried out at room temperature.

[0049] In this invention, after the reaction is complete, solid-liquid separation is performed. The preferred method of solid-liquid separation is centrifugation to collect the precipitate. After solid-liquid separation, the solid is washed and then dried. The drying method can be natural air drying or freeze drying; heat sources such as heat lamps or ovens should not be used for drying. After the above post-treatment, nickel hydroxide is obtained.

[0050] Regarding step C) :

[0051] C) The nickel hydroxide and selenium powder, as the matrix and non-metallic source precursor, are placed in a tube furnace and reacted at 300-350°C under a protective atmosphere to obtain Se1 / NiO pseudometal single-atom material.

[0052] In this invention, the preferred mass ratio of nickel hydroxide to selenium powder is (30-60) mg:(0.8-1.2) g.

[0053] In this invention, there are no special restrictions on the type of protective gas used to provide the protective atmosphere; any conventional protective gas in the art is acceptable, such as nitrogen, helium, or argon, with argon being preferred. In this invention, the inlet rate of the protective gas is preferably 200–250 mL / min, specifically 200 mL / min, 210 mL / min, 220 mL / min, 230 mL / min, 240 mL / min, or 250 mL / min.

[0054] In this invention, the reaction temperature is 300–350°C, specifically 300°C, 310°C, 320°C, 330°C, 340°C, or 350°C. The heating rate is preferably 5–10°C / min, specifically 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min. The holding time for the reaction is preferably 2–3 hours, specifically 2 hours, 2.5 hours, or 3 hours.

[0055] In this invention, the preferred specific operation process of step C) includes: placing nickel hydroxide in a ceramic boat 1, placing selenium powder in a ceramic boat 2, and placing the ceramic boat 1 and ceramic boat 2 in a quartz tube, wherein the ceramic boat 1 is placed in the middle of the quartz tube, the ceramic boat 2 is located upstream of the ceramic boat 1, a protective gas is introduced to purge the quartz tube, and the temperature is raised to 300-350°C to react, thereby obtaining Se1 / NiO pseudometal single-atom material.

[0056] In this context, "1" and "2" in "Porcelain Boat 1" and "Porcelain Boat 2" have no specific meaning or limitation; they are merely used to distinguish that they are two separate porcelain boats. The preferred distance between Porcelain Boat 1 and Porcelain Boat 2 is 10–20 cm, specifically 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 16 cm, 17 cm, 18 cm, 19 cm, or 20 cm. After purging the quartz tube with protective gas for 20–45 minutes, heating begins, and the purging with protective gas continues throughout the heating process. A continuous flow of inert gas ensures an inert atmosphere rather than an oxidizing atmosphere (because pure NiO cannot be obtained under oxidizing conditions). Furthermore, the inert gas acts as a transport carrier, and the continuous flow of gas will bring the heated and volatilized Se atoms to react with the nickel hydroxide in Porcelain Boat 1 through thermal diffusion. The purging time of 20–45 minutes can specifically be 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, or 45 minutes. The inlet rate of the protective gas is as described above and will not be repeated here. The heating procedure is as described above and will not be repeated here. After the reaction, it is preferable to further cool down and remove the material to obtain Se1 / NiO pseudometallic single-atom material.

[0057] This invention involves preparing non-metallic single-atom materials from a nickel hydroxide precursor under a programmed temperature rise in a suitable gas atmosphere via controlled solid-state thermal diffusion. Controlled thermal diffusion is employed to ensure atomically dispersed non-metallic single-atom Se. Typically, tubular furnace calcination methods mostly yield selenides. In this invention, the ratio of nickel hydroxide to selenium powder, along with the reaction atmosphere, gas flow rate, reaction temperature, and the positions of the two ceramic boats, are controlled during the preparation process to optimize the solid-state thermal diffusion path, resulting in the non-metallic single-atom material Se1 / NiO.

[0058] This invention also provides a Se1 / NiO pseudometal single-atom material prepared by the preparation method described in the above technical solution. In this invention, the Se loading in the obtained Se1 / NiO pseudometal single-atom material is 0.5wt% to 1wt%.

[0059] After detailed structural analysis, it was found that Se-Ni bonds do not exist in the Se1 / NiO nonmetallic single-atom material. Therefore, this invention provides a novel pseudometallic single-atom structure material. Based on structural characterization, it was discovered that Se occupies pseudometal sites and directly bonds with O, rather than forming Se-Ni through doping or substitution as is traditionally the case. Based on structural characterization, it was found that a small amount of Se induces the electronic state of the central metal Ni, thereby controlling the covalent nature of the Ni-O bond and the electronic excitation process of NiO. Furthermore, it was found that a small amount of Se induces the reconstruction of the electronic state of the central metal Ni, thereby achieving magnetic reversal of NiO. Therefore, this invention provides a novel method for covalent bond enhancement and band structure control. On the one hand, this invention employs a rapid solid-state thermal diffusion method. If a conventional heating-diffusion method is used, the corresponding selenide will be formed. In addition, this direct conversion of the Ni(OH)2 precursor under inert conditions is also very important. We tried replacing the inert Ar atmosphere with air, or first converting Ni(OH)2 to NiO under an inert atmosphere, and then carrying out a thermal diffusion reaction with Se. Se-Ni bonds appeared in these control experimental groups. On the other hand, conventional non-metallic element doping and non-metallic single atoms have been reported, but the non-metallic single-atom material newly created in this patent does not contain Se-Ni bonds. Structural characterization by XAFS and electron microscopy shows that it is actually a pseudo-metallic single-atom material in which the apparent non-metallic element Se occupies the position of metallic Ni in NiO. To date, there have been no reports of such a material in the world.

[0060] This invention also provides an application of the Se1 / NiO pseudometal single-atom material described in the above-mentioned technical solution as a catalyst in electrocatalytic oxygen evolution, specifically as an electrocatalytic OER catalyst for water splitting to produce oxygen. In this invention, the Se1 / NiO pseudometal single-atom material powder is first prepared into a catalyst slurry, and then sprayed onto a catalyst support such as carbon paper or a glassy carbon electrode. In the embodiments, the slurry is sprayed onto a smooth and flat glassy carbon electrode for electrocatalytic oxygen evolution to directly reflect the intrinsic catalytic activity of the catalyst (compared to carbon paper, using a glassy carbon electrode for testing can eliminate the contribution of specific surface area to catalytic activity, thus the obtained electrochemical performance data directly reflects the catalytic activity of the catalyst itself, which is an intrinsic activity. Only by comparing the intrinsic catalytic activity with the theoretical overpotential of the OER adsorption evolution mechanism is it meaningful and scientific). Using the pseudometal single-atom material created in this invention as an OER electrocatalyst breaks through the theoretical limit overpotential of the adsorption evolution mechanism in the OER process and exhibits excellent electrochemical stability. Experimental results show that the Se1 / NiO pseudometallic single-atom material of the present invention can achieve 10 mA / cm² under alkaline conditions at an overpotential of 265 mV. 2 The current density is 20 mA / cm². 2 There was no significant performance degradation even after continuous electrocatalytic water splitting for more than 25 hours.

[0061] Compared to common metallic single-atom materials, this invention innovatively targets the blank research area of ​​non-metallic single-atom materials. The easy oxidation and high electronegativity of non-metallic elements typically lead to their inclusion in the matrix material as dopant to form corresponding metal-non-metal bonds. Therefore, to date, no truly non-metallic single-atom materials have been prepared. This invention utilizes the quasi-metallic properties of Se to prepare Se-based pseudometallic single atoms with oxygen atom rivets.

[0062] Normally, the introduction of non-metallic elements into matrix materials is achieved by annealing directly in an inert atmosphere. However, due to the similar physicochemical properties of non-metallic elements, they can usually only form compounds with corresponding metal-non-metal bonds. This invention innovatively develops a rapid solid-phase thermal diffusion controllable synthesis technology to prepare Se1 / NiO pseudometal single-atom materials under the conditions of in-situ phase transformation and selenization of nickel hydroxide precursor.

[0063] From a fundamental physics perspective, the operation of any electronically-related device depends on the evolution of electronic states, but currently there is no effective method for controlling the electronic states of materials. For example, the covalent nature of the central metal-ligand relationship has shown significant influence in numerous systems, including electron transfer, H-bond effects, and olefin reaction activation. Furthermore, the electronic band excitation process of materials is closely related to their band structure and electrical properties. This invention creates a novel pseudometallic single-atom structure that enables the control of the Ni-O covalent bond and alters the energy level structure due to the introduction of specific sites on the Se single atom, achieving effective control of the electronic excitation process. This provides a practical and effective new method for the subsequent construction of specific electronic structures.

[0064] Conventional preparation of metal single-atom catalysts often involves high-temperature pyrolysis (900–1000°C), which is energy-intensive and increases the risk of failure in the growth of atomic clusters into nanoparticles. In this invention, non-metallic single-atom materials are prepared at around 300°C, reducing energy consumption and ensuring the structural stability of the prepared materials. Furthermore, the solid-state thermal diffusion experimental method used does not involve the use of strong acids or bases, making it more environmentally friendly and convenient, and particularly suitable for large-scale batch preparation of non-metallic single-atom materials.

[0065] The non-metallic single-atom material obtained by this invention greatly improves and affects the surface states and physicochemical properties of the material due to the quasi-metallicity, occupied positions, derived unique coordination modes and changes in local electron density of the non-metallic element Se. Powdered Se1 / NiO exhibits excellent intrinsic catalytic activity and stability in alkaline electrocatalytic oxygen evolution process. This newly created functional nanomaterial shows great potential for application in electrochemical energy conversion.

[0066] The Se1 / NiO pseudometallic single-atom material prepared in this invention exhibits unique elemental properties and coordination modes, especially its modulated energy level structure and electronic states, which differ from the physicochemical properties of common metallic single atoms or compounds doped with conventional non-metallic elements, thus demonstrating excellent catalytic activity and stability. In this embodiment, the Se1 / NiO non-metallic single-atom material is used as an example. The obtained electrocatalyst Se1 / NiO was placed in an alkaline electrolyte, and its electrochemical performance was tested using a general electrochemical testing device. Under alkaline conditions, the powdered Se1 / NiO non-metallic single-atom material can achieve an overpotential of 10 mA / cm² at 265 mV. 2 And at 20mA / cm 2 It continuously electrolyzes water to produce oxygen for more than 25 hours at a current density, demonstrating extremely high intrinsic catalytic activity.

[0067] In summary, this invention develops an energy-efficient, rapid, solid-phase thermal diffusion method for the controllable preparation of non-metallic single-atom materials, creating a novel Se1 / NiO pseudometallic single-atom structure. It also provides a new method for controlling energy level structure and electronic states, achieving a highly efficient OER catalytic reaction process. This method has potential applications in electrocatalytic carbon dioxide reduction, metal-air batteries, and electrocatalytic green hydrogen production. Furthermore, the solid-phase thermal diffusion controllable preparation process described in this invention is simple, energy-efficient, and the prepared non-metallic single-atom materials are easily and stably stored, promising applications in catalysis, batteries, and other photoelectric conversion fields. Finally, the unique structure prepared will provide a novel carrier and platform for materials research.

[0068] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0069] Example 1

[0070] A) Weigh 13g of nickel sulfate and dissolve it in 90mL of deionized water. After stirring thoroughly for 5 minutes, slowly add 3g of potassium persulfate to the above mixed solution and continue stirring to obtain solution A.

[0071] B) Slowly add 10 mL of industrial ammonia to solution A to adjust the pH value, continue stirring until the reaction is complete, centrifuge to collect the precipitate, wash several times with anhydrous ethanol and deionized water, freeze dry to obtain nickel hydroxide.

[0072] C) Place 50 mg of nickel hydroxide in ceramic boat 1 and 1 g of selenium powder in ceramic boat 2. Place ceramic boat 1 and ceramic boat 2 in a quartz tube, with ceramic boat 1 in the middle of the quartz tube and ceramic boat 2 upstream of ceramic boat 1. The distance between the two ceramic boats is 15 cm. Purge the quartz tube with argon gas (inlet speed of 200 mL / min) for 30 minutes, then raise the temperature to 300℃ at 10℃ / min and hold for 2 hours. After the quartz tube cools to room temperature, take out the material to obtain Se1 / NiO pseudometal single-atom material.

[0073] Product Characterization and Testing :

[0074] 1. Characterization of phase structure

[0075] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the Se1 / NiO pseudometal single-atom material obtained in Example 1. The XRD confirms that the phase of Se1 / NiO is NiO, and there is no obvious elemental selenium (Se) or selenide (NiSe2) generated, indicating that the Se element is dispersed in the NiO matrix in the form of single atoms.

[0076] Figure 2The image shows a scanning electron microscope (SEM) image (EDS) of the Se1 / NiO pseudometallic single-atom material obtained in Example 1. Figure 2 (a) is a SEM image. Figure 2 (b) is an EDS image. The scan image shows that the morphology of the synthesized material is a nanoflower structure, which confirms that Se element is indeed present in the prepared material. The small signal indicates that it is introduced at the atomic level.

[0077] Figure 3 The image shown is a high-angle annular dark-field image-scanning transmission electron microscope image of the Se1 / NiO pseudometal single-atom material obtained in Example 1, serving as direct evidence that Se exists in the material in the form of single atoms.

[0078] Figure 4 The image shows the K-edge X-ray absorption extension of Se in R space for the Se1 / NiO pseudometallic single-atom material obtained in Example 1. It can be seen that in the Se1 / NiO material, no Se-Se or Se-Ni is generated, only Se-O exists, which further indicates that Se exists in single-atom form and occupies the metal position of nickel oxide.

[0079] 2. Characterization of electronic energy level structure

[0080] According to the periodic table, the electronegativity of selenium (Se) (2.55) is weaker than that of oxygen (O) (3.44). Based on this understanding, introducing selenium into NiO would lower the valence state of metallic Ni. However, structural characterization of the sample and a reference sample (using the same experimental procedure but without selenium) using X-ray photoelectron spectroscopy (XPS) revealed that the high valence state Ni in NiO with selenium present... 3+ The fact that the amount of Se has increased indicates that the introduced Se in the Se1 / NiO material has clipped the energy level structure of NiO in an unconventional way. At the same time, the increased valence state of the central metal Ni implies enhanced Ni-O covalent bonds in the Se1 / NiO sample.

[0081] Furthermore, characterization of the energy level structure and electronic excited states of the material using state-of-the-art synchrotron resonant inelastic X-ray scattering (RIXS) revealed that the introduction of Se reduced the crystal field splitting energy (10Dq) of NiO. At the same time, compared with the undoped NiO reference sample, a spin-forbidden electronic spin-flip state appeared. This spin-flip experimental phenomenon has long been considered difficult to achieve through traditional synthesis methods or sample processing.

[0082] Figure 5 This is the XPS image of the prepared Se1 / NiO sample, showing obvious Ni. 3+ .

[0083] Figure 6The image shows the Ni L-edge synchrotron radiation resonance inelastic X-ray scattering pattern of the prepared Se1 / NiO, confirming that this structure significantly alters the energy level structure and electronic excitation process of NiO.

[0084] 3. Electrochemical performance testing

[0085] The test was conducted in a standard three-electrode system, using a Hg / HgO electrode calibrated with a standard hydrogen electrode as the reference electrode and a graphite rod as the counter electrode. For the working electrode, 4 mg of the non-metallic single-atom alloy catalyst prepared in Example 1 was weighed and dispersed in a mixture of 500 μL water, 460 μL ethanol, and 40 μL perfluorosulfonic acid polymer solution (Nafion aqueous solution, concentration 0.5%), and ultrasonicated for 1 h to ensure uniform dispersion, thus obtaining a catalyst solution. To verify that the constructed special material structure can induce changes in the electronic energy level structure of the material, thereby ultimately affecting the catalytic performance, an intrinsic catalytic activity was identified using a 3 mm diameter planar glassy carbon electrode. Specifically, the catalyst solution was sprayed onto the glassy carbon electrode and air-dried at room temperature to serve as the working electrode.

[0086] See test results Figure 7 , Figure 7 The graph shows the electrocatalytic oxygen evolution performance of the Se1 / NiO pseudometal single-atom material obtained in Example 1 under alkaline conditions. It can be seen that 10 mA / cm² can be achieved at an overpotential of 265 mV. 2 The current density is 20 mA / cm². 2 Even under high current density, continuous water electrolysis for more than 25 hours showed no significant performance degradation, confirming its great application potential for the anodic oxygen evolution reaction in electrocatalytic water splitting.

[0087] 4. Magnetic performance test

[0088] Using the Se1 / NiO pseudometallic single-atom material obtained in Example 1 as the test sample and NiO as the reference sample, its MH curve was tested at room temperature, and the results are as follows. Figure 8 As shown, the NiO reference sample exhibits significant magnetism, but its magnetism weakens considerably after the introduction of the Se structure. This indicates that the introduction of Se significantly alters the electronic structure of the material, leading to a change in its magnetic structure.

[0089] Example 2

[0090] The procedure was carried out as described in Example 1, except that in step C), the argon gas inlet rate was 250 mL / min, the heating rate was 5 °C / min, and the reaction temperature was 350 °C.

[0091] Comparative Example 1

[0092] The procedure was carried out as in Example 1, except that the amount of Se powder was adjusted to 0.5g.

[0093] Comparative Example 2

[0094] The procedure was carried out as in Example 1, except that the argon gas inlet rate was 260 mL / min.

[0095] Comparative Example 3

[0096] The procedure was carried out as in Example 1, except that the reaction temperature in step C) was adjusted to 250°C.

[0097] Comparative Example 4

[0098] The procedure was carried out as in Example 1, except that the nickel hydroxide in step C) was replaced with commercial Ni(OH)2 (purchased from Aladdin Reagents, which was not further treated before use).

[0099] Comparative Example 5

[0100] The process was carried out according to Example 1, except that in Example 1, the Ni(OH)2 precursor conversion and Se oxidation were carried out simultaneously, both in an inert atmosphere (i.e., step C). In this Comparative Example 5, this simultaneous process was divided into two steps: first, the Ni(OH)2 precursor was converted to NiO under air conditions, and then Se oxidation was carried out under the same conditions after the reaction was completed. Specifically, the operation of step C) was changed to the following process: 50 mg of nickel hydroxide was placed in a ceramic boat 1, and the temperature was increased to 300°C at 10°C / min and kept at that temperature for 1 hour under air conditions. After the quartz tube cooled to room temperature, 1 g of selenium powder was placed in a ceramic boat 2, and the ceramic boat 2 was placed upstream of the ceramic boat 1, with a distance of 15 cm between the two ceramic boats. Argon gas (inlet rate of 200 mL / min) was introduced to purge the quartz tube for 30 minutes, and then the temperature was increased to 300°C at 10°C / min and kept at that temperature for 1 hour. After the quartz tube cooled to room temperature, the material was taken out to obtain the control sample in Comparative Example 5.

[0101] Comparative Example 6

[0102] The process was carried out according to Example 1, except that in Example 1, the Ni(OH)2 precursor conversion and Se oxidation were carried out simultaneously. In this Comparative Example 6, this synchronous process was divided into two steps: first, the Ni(OH)2 precursor was converted into NiO under the same conditions, and then Se oxidation was carried out under the same conditions after the reaction was completed. Specifically, the operation of step C) was changed to the following process: 50 mg of nickel hydroxide was placed in a ceramic boat 1, and the ceramic boat 1 was placed in a quartz tube. Argon gas was introduced (inlet rate of 200 mL / min) to purge the quartz tube for 30 minutes. Then, the temperature was increased to 300°C at 10°C / min and kept at that temperature for 1 hour. After the quartz tube cooled to room temperature, the reaction was carried out. Place 1g of selenium powder in a ceramic boat 2 and place the ceramic boat 2 upstream of the ceramic boat 1, with a distance of 15cm between the two ceramic boats. Purge the quartz tube with argon gas (inlet speed of 200mL / min) for 30 minutes, then raise the temperature to 300℃ at 10℃ / min and keep it at that temperature for 1 hour. After the quartz tube cools to room temperature, take out the material to obtain the control sample in Comparative Example 6.

[0103] Examples 2 and Comparative Examples 1-7 were tested according to the electrochemical performance testing method in Example 1, and the results are shown in Table 1.

[0104] Table 1: Experimental results of each embodiment and comparative example

[0105]

[0106] As can be seen from the above embodiments, the preparation method of non-metallic single-atom materials using solid-phase thermal diffusion in this invention is simple and energy-efficient. By controlling the appropriate thermal diffusion reaction temperature and the ratio of precursors to non-metallic elements, a novel Se1 / NiO pseudometallic single-atom structure can be obtained, which significantly alters the electronic and band structure of the NiO matrix. Taking the Se1 / NiO prepared in this invention as an example, during the electrocatalytic cracking of water to produce oxygen under strongly alkaline conditions, it can reach an overpotential of 10 mA / cm² at only 265 mV. 2 And at 20mA / cm 2 Even after continuous electrolysis at high current density for more than 25 hours, there was no significant performance degradation. This excellent electrocatalytic activity indicates that the newly created non-metallic single-atom catalyst exhibits high catalytic activity because the change in local electron density induced by the pseudometal Se greatly improves the surface state properties of the material.

[0107] Compared with Examples 1-2, Comparative Examples 1-6 either failed to form pseudo-metal single-atom structures or formed pseudo-metal single-atom structures but with reduced electrocatalytic activity (the stability of Comparative Examples 1-4 was not tested because their electrocatalytic activity was insufficient, so there was no need to test the stability). This demonstrates that the innovative rapid solid-phase thermal diffusion method developed in this invention, by controlling the ratio of nickel hydroxide to selenium powder, the inlet rate of the protective gas, the reaction conditions, and the nickel hydroxide synthesized using a specific method, can create novel pseudo-metal single-atom structures and exhibit effects that are beneficial to improving the electrochemical performance of the catalyst.

[0108] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a Se1 / NiO pseudometallic single-atom material, characterized in that, Includes the following steps: A) Mix nickel sulfate, water, and potassium persulfate to obtain solution A; B) Add ammonia to solution A to adjust the pH value. After the reaction is complete, separate the solid and liquid, wash and dry to obtain nickel hydroxide. C) Place nickel hydroxide in a ceramic boat 1, place selenium powder in a ceramic boat 2, and place the ceramic boat 1 and ceramic boat 2 in a quartz tube, wherein the ceramic boat 1 is placed in the middle of the quartz tube and the ceramic boat 2 is located upstream of the ceramic boat 1. Purge the quartz tube with a protective gas and heat to 300~350℃ to react and obtain Se1 / NiO pseudometal single-atom material. The distance between porcelain boat 1 and porcelain boat 2 is 10~20cm; The mass ratio of nickel hydroxide to selenium powder is (30~60) mg : (0.8~1.2) g; The intake rate of the protective gas is 200~250 mL / min.

2. The preparation method according to claim 1, characterized in that, In step C), the heating rate is 5~10℃ / min.

3. The preparation method according to claim 1, characterized in that, In step A), the mass ratio of nickel sulfate to potassium persulfate is (10~15):

3.

4. The preparation method according to claim 1, characterized in that, The ratio of ammonia in step B) to nickel sulfate in step A) is (5~15) mL : (10~15) g.

5. A Se1 / NiO pseudometallic single-atom material prepared by any one of claims 1 to 4.

6. The application of the Se1 / NiO pseudometal single-atom material as described in claim 5 as a catalyst in electrocatalytic oxygen evolution.

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