A method for preparing a single-atom Ni-modified AuNi alloy catalyst and its application

Abstract

This invention discloses a method for preparing a single-atom Ni-modified AuNi alloy catalyst and its application. Employing a simple and efficient one-step photodeposition method, without the need for high-temperature annealing or reducing atmosphere treatment, the method simultaneously achieves the formation of AuNi alloy and the precise introduction of single-atom Ni on the surface of Au nanoparticles. The synergistic effect between the two significantly enhances the adsorption and activation capacity of reactant molecules and effectively promotes the separation and transport of photogenerated carriers, thereby achieving the efficient conversion of CO into the high-value-added fuel CH4 in the CO2 reduction reaction. The catalyst prepared by this invention significantly increases the number of catalytic active sites while reducing the amount of precious metal Au used. It exhibits higher activity, selectivity, and stability during the catalytic process, fully demonstrating the broad application prospects of this material in the field of low-carbon conversion.

Description

Technical Field

[0001] This invention belongs to the field of composite photocatalytic material preparation technology, specifically relating to a method for preparing a single-atom Ni-modified AuNi alloy catalyst and its application. Background Technology

[0002] Since the Industrial Revolution, human society has consumed vast amounts of fossil fuels to support economic development and population growth, leading to a rapid increase in atmospheric carbon dioxide (CO2) concentration. It is predicted that by the end of this century, atmospheric CO2 concentration may reach three times the level at the beginning of the Industrial Revolution (approximately 270 ppm), far exceeding the internationally recognized safe threshold of 350 ppm. Therefore, under the "dual carbon target" framework, there is an urgent need for advanced technologies capable of converting CO2 into valuable chemicals / fuels to achieve a "closed-loop" utilization of CO2 resources. In recent years, artificial photosynthesis, mimicking the complete photosynthesis reaction of plants in nature, has received widespread attention both domestically and internationally. This is because this technology can convert the greenhouse gas CO2 into CO, CH4, CH3OH, and even C under sunlight and water (H2O) conditions. 2+ This technology, which produces value-added products, is considered a promising technology. Its implementation can not only achieve the green cycle and sustainable use of carbon resources, but also significantly reduce the concentration of CO2 in the atmosphere, which is of great significance for alleviating the energy crisis and protecting the environment.

[0003] Noble metals such as gold (Au), with their unique geometric and electronic structures, can effectively modulate light absorption due to their typical plasmon resonance (SPR) effect and semiconductor-like d-electron interband transition characteristics. By collecting photons to generate high-energy electrons, they can increase the local electron density of surface adsorption sites, thereby achieving high CO2 conversion efficiency. However, the high cost of noble metals increases the preparation cost of catalysts, making it difficult to meet the economic requirements of practical applications. Furthermore, as photocatalysts, pure noble metals, due to their filled or half-filled d-orbitals and low d-band centers, have weak chemisorption capacity for reactant molecules, resulting in limited photocatalytic efficiency. In recent years, researchers have attracted widespread attention by introducing non-noble metals to construct nano-alloy particles, enhancing catalytic activity while reducing the amount of noble metals used. The strong synergistic effect between metals in these alloys can form excellent coordination structures and optimized electronic environments. Compared with single-metal catalysts, bimetallic catalytic materials help improve light absorption and regulate the separation and migration kinetics of photogenerated carriers at the interface, making them ideal metal catalysts for improving and controlling catalytic activity and selectivity.

[0004] However, most alloy catalysts currently suffer from problems such as single catalytic active sites and insufficient activity. Furthermore, existing alloy catalyst preparation processes are generally complex and demanding (e.g., the high-temperature hydrogen reduction method is not only unsafe but also cumbersome), and these metal-based catalytic materials exhibit poor adsorption and activation capabilities for reactant molecules, limiting the rational design and optimization of catalysts. Therefore, there is an urgent need to improve the activity and stability of alloy nano-metal catalysts through modification strategies. Integrating multi-scale sites, such as single atoms and nano-alloy particles, to construct synergistic catalytic sites is a highly effective approach. The composite of synergistic components can effectively regulate the electronic structure of active sites, thereby adjusting the adsorption strength of reaction intermediates, improving reaction kinetics, and maximizing catalytic activity. However, a simple, rapid, and stable preparation method for such single-atom modified nano-alloy materials is currently lacking. Therefore, developing efficient, economical, stable, and easy-to-operate methods for preparing single-atom modified nano-alloy metal catalytic materials has become a key research focus, aiming to promote the practical application of high-performance photocatalysts in fields such as CO2 reduction. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for preparing single-atom Ni-modified AuNi alloy catalysts using a one-step photodeposition method and its application. This method utilizes AuNi nano-alloy particles with plasmon resonance (SPR) effects as enhanced CO2 reduction activity centers and regulating sites for carrier separation, while simultaneously introducing Ni single atoms as effective adsorption and activation sites for reactant molecules. This allows the constructed catalyst structure to effectively reduce the amount of precious metal Au used, while achieving highly efficient electron-hole pair separation through a synergistic effect, significantly improving CO2 reduction activity, and regulating the conversion of the product CO into the high-value-added fuel CH4.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention first discloses a method for preparing a single-atom Ni-modified AuNi alloy catalyst, comprising the following steps:

[0008] Step 1: Add AlOOH support to Au nanoparticle solution, and then use ultrasound and mechanical stirring to allow AlOOH and Au nanoparticles to self-assemble under electrostatic interaction. Collect the precipitate by centrifugation and washing with water. After freeze-drying the precipitate, anneal it to obtain Au nanoparticle-supported AlOOH composite material, denoted as Au / AlOOH.

[0009] Step 2: The Au / AlOOH composite material obtained in Step 1 is added to deionized water and ultrasonically dispersed until uniform. Then, Ni salt solution and methanol are added under vigorous stirring to obtain a suspension. The suspension is irradiated with ultraviolet light in an inert gas atmosphere to reduce Ni salt by photo-excitation of electrons generated synergistically by Au nanoparticles and AlOOH. After irradiation, the resulting solution is centrifuged, washed with water, and the precipitate is collected and dried to obtain a single-atom Ni-modified AuNi alloy photocatalyst, denoted as AuNi-Ni. SAC / AlOOH.

[0010] Preferably, in step 1, the annealing treatment is carried out at a temperature of 200–600°C for 1–2 hours.

[0011] Preferably, in step 1, the concentration of the Au nanoparticle solution is 0.1-1 mM, and the ratio of AlOOH support to Au nanoparticle solution is 0.1-2.5 g / 103 mL.

[0012] Preferably, in step 1, the Au nanoparticles have a particle size of 4-12 nm. Studies have shown that the particle size of Au nanoparticles has a significant impact on the photodeposition reduction process. When the size of Au nanoparticles is less than 4 nm, due to the enhanced size effect, Au tends to cluster, resulting in an incomplete lattice structure and a decrease in the coordination number of surface atoms, thereby reducing the overall structural stability. When the particle size exceeds 12 nm, the surface plasmon resonance (SPR) effect is significantly enhanced, resulting in extremely short lifetimes of the generated non-equilibrium hot carriers (only in the femtosecond range), which are insufficient to effectively participate in the Ni reduction reaction. Therefore, selecting a particle size range of 4-12 nm can avoid the instability of clustering caused by excessively small size, and suppress the phenomenon of SPR effect dominating due to excessively large size, thus facilitating the excitation of interband transitions in Au and generating photogenerated electrons with longer lifetimes (up to the nanosecond level). Based on this, the photoexcited electrons are then transferred to the Ni salt adsorbed on the surface of Au nanoparticles and AlOOH, realizing the efficient preparation of single-atom Ni-modified AuNi alloy catalysts.

[0013] Preferably, in step 2, the Ni salt is selected from any one of Ni(NO3)2, NiCl2, NiSO4, and Ni(acac)2.

[0014] Preferably, in step 2, the concentration of the Ni salt solution is set to 10 g / L, and the ratio of Au / AlOOH composite material, deionized water, Ni salt solution, and methanol is 1.0 g: 50–150 mL: 10–100 mL: 30–100 mL. During photodeposition, methanol plays a crucial role as a sacrificial agent in consuming holes and in the overall photodeposition efficiency. Methanol can rapidly react with photoexcited holes, effectively consuming them, thereby inhibiting electron-hole recombination and prolonging the lifetime of photogenerated electrons. This is particularly important for metallic Ni. 2 The efficient reduction of + is crucial. An appropriate amount of methanol (30–100 mL) helps to fully activate photogenerated electrons to participate in the reduction reaction, but excessive methanol (>100 mL) may introduce excessively high concentrations of intermediate oxidation products (such as formaldehyde or formic acid). These intermediate products may adsorb onto the catalyst surface to some extent, thereby altering the catalyst's surface properties or interfering with the adsorption of reactants. Furthermore, excessive organic components in the reaction system may also perturb the light absorption process, reduce photoexcitation efficiency, and thus indirectly affect the reduction kinetics of metal ions.

[0015] Preferably, in step 2, the wavelength of the ultraviolet light irradiation is 250–350 nm, and the irradiation time is 60–300 minutes. In contrast, visible light mainly induces the SPR effect, which produces electrons with short lifetimes and low energy. Ultraviolet light, however, can effectively excite the interband transition effect of Au nanoparticles, thereby generating photogenerated electrons with longer lifetimes. These electrons can fully participate in and drive Ni... 2+ The reduction process of Ni. Therefore, using ultraviolet light as the main light source in the photodeposition process can significantly improve the reduction process of Ni. 2 + The efficiency of reduction is improved, thereby achieving better reaction performance during catalyst construction.

[0016] Preferably, photodeposition reduction is carried out in an inert atmosphere to maintain the stability of the AuNi alloy structure and single-atom Ni.

[0017] This invention further discloses a single-atom Ni-modified AuNi alloy catalyst prepared according to the above preparation method. The catalyst comprises an AlOOH support and a metallic active component supported on the AlOOH support. The metallic active component consists of AuNi nano-alloy particles and single-atom Ni particles. The AuNi nano-alloy particles have a particle size of 5-15 nm.

[0018] The present invention also discloses the application of the single-atom Ni-modified AuNi alloy catalyst in the photocatalytic CO2 reduction reaction, which can efficiently convert CO2 into CH4.

[0019] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0020] 1) This invention employs a simple and mild one-step photodeposition method to introduce Ni species. This method not only forms AuNi alloys with the noble metal Au, but also precisely introduces Ni single atoms with unique effects. The operation process is simple, requiring no high-temperature annealing or reducing atmosphere treatment, significantly simplifying the preparation process. Furthermore, the mild preparation conditions help maintain the stability of the alloy structure and single atoms, ensuring the consistency of catalyst performance.

[0021] 2) The introduction of single-atom Ni significantly enhances the adsorption and activation of reactant molecules by the catalyst. This enhanced adsorption capacity promotes the efficient reduction of CO2 and the efficient dissociation of H2O, generating more reaction intermediates. In addition, the high dispersion of Ni single atoms ensures the uniformity of active sites, further improving the selectivity of the catalyst for reactants and the reaction kinetics, thereby significantly improving the overall efficiency of the photocatalytic reaction.

[0022] 3) Single-atom Ni modification of pure AuNi alloy catalysts can further optimize the electronic structure and geometry of active sites, thereby significantly improving the selectivity and efficiency of CO to CH4 conversion in CO2 reduction reaction.

[0023] 4) The construction of the AuNi alloy not only effectively reduces the amount of precious metal Au used, but also significantly improves the separation and transport efficiency of photogenerated electron-hole pairs. Only 1–5 wt% Ni metal atoms are required to increase the reaction yield by more than two times, and the amount of transition metal atoms added is at least 1–3 orders of magnitude lower than existing technologies, resulting in low cost and high efficiency. Moreover, this characteristic enhances the selectivity and overall CO2 conversion activity of the photocatalytic reduction of CO2 to CH4. Stability tests show that the catalyst of this invention exhibits excellent catalytic activity, selectivity, and stability under visible light irradiation, and its catalytic performance shows no significant decay after 8 hours of continuous reaction, demonstrating broad application prospects in the field of sustainable energy.

[0024] 5) The preparation method of this invention effectively overcomes the shortcomings of existing technologies, such as cumbersome preparation process, low catalyst yield, and unstable structure. It focuses on solving the problems of weak adsorption capacity of metal nanostructures for reactant molecules and insufficient active sites. This preparation method has the advantages of being economical, efficient, and easy to operate. Attached Figure Description

[0025] Figure 1 The AlOOH, Au / AlOOH, and AuNi-Ni prepared in the examples are as follows. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC XRD pattern of AlOOH-3.

[0026] Figure 2 In the series (a) to (d), the values ​​are AuNi-Ni respectively. SAC Transmission electron microscopy (TEM) images, particle size distribution maps, high-resolution TEM images, and AC-HAADF-STEM images of AlOOH-2, with (e) to (i) showing AuNi-Ni under a 50 nm scale, respectively. SAC Transmission electron microscopy image of / AlOOH-2 and corresponding EDS elemental distribution maps of O, Al, Au, and Ni.

[0027] Figure 3 The images (a) through (c) are transmission electron microscopy (TEM) images, high-resolution TEM images, and particle size distribution diagrams of the Au / AlOOH samples, respectively.

[0028] Figure 4 The AlOOH, Au / AlOOH, Ni / AlOOH, and AuNi-Ni prepared in the examples are as follows. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC XPS plot of the UV-Vis diffuse reflectance spectrum of AlOOH-3;

[0029] Figure 5 (a) in the figure represents Au / AlOOH and AuNi-Ni. SAC XPS full spectrum of AlOOH-2 sample, (b) is AuNi-Ni SAC High-resolution XPS spectra of Ni 2p in / AlOOH-2, (c) and (d) are Au / AlOOH and AuNi-Ni, respectively. SAC High-resolution XPS spectra of Au 4f(c) and Al 2p(d) of the AlOOH-2 sample.

[0030] Figure 6 The AlOOH, Au / AlOOH, Ni / AlOOH, AuNi / AlOOH, and AuNi-Ni prepared in the examples are as follows. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC A comparison of the photocatalyst performance of / AlOOH-3, where: (a) is the yield of reduction products CO, H2, and CH4; (b) is the selectivity for CO, H2, and CH4 products; and (c) is the performance of AuNi-Ni. SAC The yields of CO, H2, and CH4 in the AlOOH-2 photocatalyst change with reaction time; (d) shows the yields of AuNi-Ni under different light intensities. SAC CO yield of AlOOH-2.

[0031] Figure 7The Au / AlOOH, Ni / AlOOH, and AuNi-Ni prepared in the examples are shown. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC (a) Photoluminescence spectrum and (b) Time-resolved fluorescence spectrum of / AlOOH-3. Detailed Implementation

[0032] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or extraction methods not mentioned in detail are process steps or extraction methods known to those skilled in the art; and all instruments and equipment used in the following embodiments, unless otherwise specified, are standard laboratory instruments and equipment.

[0033] In the following embodiments, efforts have been made to ensure the accuracy of the figures used (including quantities, temperatures, reaction times, etc.), but some experimental errors and biases should be taken into account.

[0034] Example 1

[0035] This embodiment prepares a single-atom Ni-modified AuNi alloy catalyst according to the following steps:

[0036] 1) Layered boehmite (AlOOH) support prepared by microemulsion method

[0037] 100 mL of cyclohexane and 20 mg of polyethylene glycol were mixed and stirred at 50 °C for 30 min. Then, 20 mL of 0.3 mM aluminum nitrate and 3.5 mL of ammonia solution (27 wt%) were added sequentially, and stirring continued for another 30 min. The mixture was aged overnight at room temperature. Next, 30 mL of isopropanol was added to the system and stirred for 5 min. The mixture was washed three times with deionized water and ethanol (10000 rpm, 5 min each time). The precipitate was collected and dried overnight in a vacuum oven at 60 °C to obtain a white powder. Finally, the powder was calcined in a muffle furnace at 450 °C (heating rate 5 °C / min) for 2 h to obtain the AlOOH support.

[0038] 2) Preparation of Au nanoparticles

[0039] 3 mL of ice-bathed NaBH4 solution (0.1 M) was quickly added to 100 mL of 0.25 mM HAuCl4·xH2O solution. At this time, the solution color changed from pale yellow to wine red. After stirring for 30 min, the resulting Au nanoparticle (Au NPs) solution was allowed to stand for aging for 24 h to completely hydrolyze the unreacted NaBH4. It was then left to stand for later use.

[0040] 3) Preparation of Au nanoparticles loaded with AlOOH

[0041] 1 g of AlOOH obtained in step 1) was dispersed in 103 mL of AuNPs solution (Au NPs concentration of 0.5 mM) obtained in step 2). After sonication for 15 min, the solution was continuously stirred at room temperature for 24 h. The pink precipitate was collected by centrifugation and washing with water (centrifugation speed 10000 rpm, 5 min). The obtained precipitate was placed in a freeze dryer overnight, and then calcined in a muffle furnace at 400 °C (heating rate of 1.25 °C / min) for 2 h to obtain the Au / AlOOH composite material.

[0042] 4) Preparation of single-atom Ni-modified AuNi alloy catalysts

[0043] 1.0 g of the Au / AlOOH composite powder prepared in step 3) was dispersed in 100 mL of deionized water and sonicated for 15 min. Ni(NO3)2·3H2O solution (10 g / L) was added under vigorous stirring, and stirring continued for 3 h. Then, 50 mL of CH3OH was added to obtain a suspension. The suspension was irradiated with ultraviolet light at a wavelength of 320 nm under an argon atmosphere for 3 h. Finally, the resulting solution was washed with ultrapure water and centrifuged at 10000 rpm for 10 min. After three cycles, the precipitate was dried in a vacuum oven at 80 °C for 12 h to obtain a single-atom Ni-modified AuNi alloy photocatalyst, denoted as AuNi-Ni. SAC The amounts of Ni(NO3)2·3H2O solution were adjusted to 5 mL, 15 mL, and 25 mL using AlOOH, and the resulting samples were labeled AuNi-Ni. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2、AuNi-Ni SAC / AlOOH-3.

[0044] In addition, the following samples were prepared for comparison in this embodiment:

[0045] Au / AlOOH: the Au / AlOOH composite material obtained in step 3) above.

[0046] Ni / AlOOH: Replace the Au / AlOOH composite material in step 4) above with an equal amount of pure AlOOH support, and set the amount of Ni(NO3)2·3H2O solution added to 15mL. The resulting sample is Ni / AlOOH.

[0047] AuNi / AlOOH: Weigh 150 mg Ni(NO3)2·6H2O and dissolve it in 100 mL of 0.25 mM HAuCl4·xH2O solution; then add 1 g AlOOH support. After ultrasonic dispersion for 30 min, the system is magnetically stirred and heated to 80 °C to gradually evaporate the solvent. The resulting solid powder is first vacuum dried at 80 °C, then ground into a fine powder, and then placed in a 5 vol% H2 / Ar mixed atmosphere and annealed at 400 °C for 1 h to obtain the AuNi / AlOOH catalyst.

[0048] The samples prepared in this embodiment were characterized as follows:

[0049] 1. Structural characterization:

[0050] First, the crystallinity and phase purity of the product were determined by XRD analysis. For example... Figure 1 As shown, the diffraction peaks of the prepared AlOOH support are clearly visible. However, the AuNi-Ni... SAC No diffraction peaks related to metals Au and Ni were observed in the AlOOH sample, and no diffraction peaks related to Ni crystals were observed even when the Ni loading was increased to 5 wt% (JCPDS No. 21-1307). This may be because the loading of Au and Ni on the AlOOH surface is too low, and they are highly dispersed on the support, resulting in crystallinity below the detection limit of XRD.

[0051] 2. Morphological characteristics:

[0052] The prepared single-atom Ni-modified AuNi alloy catalyst (AuNi-Ni) was analyzed by transmission electron microscopy. SAC The morphology, dispersibility, and elemental distribution of (AlOOH-2) were characterized. Figure 2 As shown in Figure a, relatively uniformly dispersed spherical nanoparticles can be clearly seen, and their particle size distribution is shown in the figure below. Figure 2 As shown in b, the average particle size of the nanoparticles is approximately 5.5 nm, which is larger than the average particle size distribution of Au in Au / AlOOH (4.5 nm). Figure 3 As shown in the image, Ni may be present in the Au phase, leading to an increase in nanoparticle size. HRTEM image ( Figure 2c) Clear lattice fringes are shown in the figure. The lattice spacings are 0.22 nm, 0.23 nm, and 0.235 nm, which correspond to the (111) plane of the AuNi nanoalloy, the (031) plane of the AlOOH support, and the (111) plane of Au, respectively. This indicates that the prepared AuNi-Ni SAC AuNi alloy exists within the AlOOH-2 phase. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was used to examine the AuNi-Ni alloy. SAC The AlOOH-2 sample was observed. Figure 2 As shown in diagram d, numerous dispersed bright spots (circles) with a size of approximately 0.3 nm were observed around the Au-Ni alloy nanoparticles, indicating that isolated Ni sites are dispersed on the AlOOH surface. The elemental distribution diagram of Au shows (…). Figure 2 Au is mainly distributed as nanoparticles on the AlOOH support. Figure 2 The Ni species were observed to be relatively uniformly dispersed, and a large number of Ni species were present on the AuNPs, further indicating the formation of the Ni-Au alloy. Furthermore, uniformly dispersed individual Ni elements were observed near the AuNi nanoalloy particles, indicating that the introduction of Ni species both formed an AuNi alloy with Au and existed as single atoms on the support surface. These morphological characteristics confirm the successful preparation of single-atom Ni-modified AuNi alloy catalytic materials.

[0053] 3. Light absorption characterization:

[0054] To investigate the effect of Ni species introduction on the light absorption properties of Au / AlOOH, the light absorption properties of the catalyst material were analyzed and tested using solid-state ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Figure 4 As shown, the absorption band edge of Ni / AlOOH is around 450 nm, exhibiting limited absorption only below 450 nm. Due to the localized plasmon resonance effect of Au NPs (LSPR, at 520 nm), Au / AlOOH and AuNi-Ni... SACThe / AlOOH sample exhibits absorption in the 250-800 nm range, with particularly strong absorption in the visible light region. Notably, the introduction of Ni species reduces the intensity of the LSPR peak, and as the Ni content increases from 1 wt% to 5 wt%, the LSPR absorption peak continuously decreases and exhibits a redshift, consistent with the characteristics of metal alloying. This indicates that the introduction of Ni species alters the Au NPs structure, achieving Au-Ni alloying. Therefore, based on the above analytical results, it can be concluded that under light irradiation, Au, exhibiting the LSPR effect, acts as an electron donor, while Ni species, acting as an electron acceptor, can effectively promote the generation and separation of photogenerated electrons and holes.

[0055] 4. Structural and valence state characterization:

[0056] The AuNi-Ni was studied using X-ray photoelectron spectroscopy (XPS). SAC Surface chemical composition and elemental valence states of / AlOOH-2. Figure 5 Figure a shows the XPS full spectra of the samples before and after Ni addition. As can be seen from the figure, both samples contain C, Au, Al, and O elements. However, no obvious characteristic peaks of Ni were observed in the spectrum of the Ni-added sample, which is due to the relatively low Ni content and its high dispersion. Figure 5 b is AuNi-Ni SAC The high-resolution fine spectrum of Ni in / AlOOH-2 shows multiple sub-peaks in the Ni 2p spectrum due to multiple splitting and satellite peaks. The binding energy peak is at 857.2 eV, accompanied by a satellite binding energy peak at 862.1 eV, which corresponds to the Ni 2p... 3 / 2 The orbital binding energy is 874.9 eV, with a satellite peak at 879.8 eV, corresponding to Ni2p. 1 / 2 Orbit. Ni 2p 3 / 2 and Ni 2p 1 / 2 The main binding energy peak spacing is 17.7 eV, which is typical for Ni. 2+ The marker. Furthermore, the peaks at 849.8 eV and 868.4 eV are attributed to metallic Ni. 0 This indicates AuNi-Ni SAC Ni is also present in AlOOH-2. 0 This is consistent with the results of the TEM analysis mentioned above. Figure 5 c shows the high-resolution XPS spectra of Au 4f in the Au / AlOOH samples before and after the addition of Ni. The figure displays Au 4f... 7 / 2 and Au 4f 5 / 2 The two split orbitals are located at 83.6 and 87.2 eV, respectively, which correspond to the metallic Au state. 0And no other peaks appeared. In AuNi-Ni... SAC In the Au 4f spectrum of / AlOOH-2, it was found that after the introduction of Ni species, Au 4f... 7 / 2 and Au 4f 5 / 2 The binding energies shifted positively to 84.1 and 87.7 eV, respectively, indicating that electrons were transferred from Au to Ni. Figure 5 d shows the high-resolution XPS spectra of Al 2p before and after the introduction of Ni. It can be seen that AuNi-Ni after the introduction of Ni... SAC The peak position of Al 2p in the / AlOOH-2 sample is consistent with that in Au / AlOOH, both located at 74.3 eV. This indicates that the introduction of Ni has no effect on the electronic structure of the inert support AlOOH. Electron transfer only occurs between Au and Ni, which makes it difficult for Au and Ni to exert a strong interaction with AlOOH. AlOOH only plays the role of support.

[0057] 5. Evaluation of the photocatalytic CO2 activity of the catalytic material:

[0058] The photocatalytic CO2 reduction reaction was carried out in a stainless steel reaction vessel (approximately 450 mL in volume), with a quartz window at the top for light irradiation. The temperature of the reaction system was controlled by an external heating element. A 300W xenon lamp (Pofil, Beijing) was used as the light source. The light source was positioned 13.5 cm above the catalyst surface. Before the photocatalytic reaction test, a certain amount of catalyst was weighed and placed in a glass container, which was then placed inside the reaction vessel. After sealing, high-purity Ar gas (99.999%) was introduced for 30 minutes to ensure complete replacement of the air in the reaction vessel. The reactant CO2 was then injected into the reaction vessel using a syringe. Subsequently, the light source was turned on for photocatalytic activity testing. A certain amount of gas was extracted from the reaction vessel every hour, and the products were qualitatively and quantitatively analyzed by chromatography. The gaseous products were quantitatively calculated using the external standard method, and the yield was expressed in μmol / g. -1 h -1 Expression. CO2 reducing activity, selectivity, and durability tests, such as... Figure 6 As shown. Figure 6 Figure a shows the average generation rates of CH4, H2, and CO during the photocatalytic CO2 reduction process for each photocatalyst. As can be seen from the figure, Au / AlOOH exhibits only CO as the sole product, with a generation rate of 66.57 μmol g. -1 h -1 The introduction of Ni species into Au / AlOOH significantly enhanced the photocatalytic activity. This indicates that Ni species, as a co-catalyst, may play an important role in improving charge separation and providing reactive sites. Notably, in addition to CO products, CH4 and H2 reduction products were also detected. Specifically, the AuNi-Ni sample... SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC The yields of CO, the main product of AlOOH-3, were 83.11, 130.61, and 56.78 μmol g, respectively. -1 h -1 Correspondingly, CH4 production was lower than CO production, with yields of 7.60, 12.27, and 6.93 μmol g, respectively. -1 h -1 The yields of H2 were 45.95, 65.79, and 53.66 μmol g, respectively. -1 h -1 The above analysis reveals that, with the increase of AuNi-Ni... SAC As the Ni content in AlOOH gradually increases from 0 to 3.0 wt%, the CO formation rate gradually increases. Among them, AuNi-Ni... SAC The Ni / AlOOH-2 group exhibited the highest CO yield, approximately twice that of Au / AlOOH, indicating optimal Ni loading. Further increasing the Ni content to 5.0 wt% resulted in a decrease in CO yield, leading to reduced photocatalytic activity. This may be attributed to the formation of new sites for photoinduced carrier recombination due to excessively high Ni content. For Ni / AlOOH, only CO and H2 were detected, with yields of 16.34 and 13.98 μmol g, respectively. -1 h -1 This may be due to the lack of Au as an electron donor in the material, making it difficult for 8e electrons to be generated. - The reduction of CO2. Therefore, loading Ni onto Au / AlOOH significantly enhances its photocatalytic activity, attributed to the transfer of photogenerated electrons from the AuNPs surface to metallic Ni under light irradiation, effectively promoting charge separation and transfer, and thus enhancing photocatalytic activity. Furthermore, the selectivity of the products CO, H2, and CH4 was compared. Figure 6 As shown in b, the CO selectivity of Au / AlOOH is 100%. When the Ni content increases from 0 wt% to 3.0 wt%, the CO selectivity decreases from 100% to 47.0%, accompanied by the production of CH4 and H2. This indicates that the introduction of Ni reduces CO selectivity. It is noteworthy that in AuNi-Ni... SACIn the / AlOOH-2 sample, the selectivity for CH4 reached a maximum of 29.3%, and for H2, it was 23.7%, indicating that the introduction of Ni facilitated further proton-electron coupling of *CO, promoting its conversion to CH4. Further increasing the Ni content to 5.0 wt% decreased the CH4 selectivity to 20.0%, and the CO selectivity further decreased to 41.1%, while the H2 selectivity increased to 38.8 wt%, indicating that higher Ni content was detrimental to the conversion of *CO to CH4, with protons more likely to be used for H2 production. Therefore, the above results show that the introduction of an appropriate amount of Ni promotes the conversion of *CO to CH4.

[0059] like Figure 6 As shown in Figure c, the optimized catalyst AuNi-Ni exhibits performance at 200°C under LED-420nm illumination. SAC The yields of CO, H2, and CH4 products on the AlOOH-2 surface change with illumination time. The figure shows that within 8 hours of reaction, the production of each product increases with increasing illumination time. The final yields of CO, H2, and CH4 within 8 hours are 741.83, 487.60, and 129.23 μmol g, respectively. -1 Furthermore, the catalyst showed no significant deactivation during the photocatalytic process, indicating that it possesses good stability. Figure 6 Figure d shows the photocatalytic activity of the LED-420nm irradiation source after adjusting the light intensity using a light intensity modulator. As can be seen from the figure, the CO yield increases linearly with increasing light intensity. This linear dependence indicates that the photocatalytic reduction of CO2 is primarily an electron-driven process.

[0060] 6. Characterization of carrier separation efficiency:

[0061] Steady-state (PL) / transient (TRPL) fluorescence and photoelectrochemical characterization were performed on various photocatalytic materials. For example... Figure 7 As shown in figure a, steady-state photoluminescence (PL) spectroscopy was first performed on the samples to further investigate the recombination rate of photogenerated carriers. As can be seen from the figure, all samples exhibited strong fluorescence intensity under 340 nm light excitation. Compared to single-metal Ni / AlOOH and Au / AlOOH, AuNi-Ni... SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC The weakening of the main fluorescence peak and the extended photoluminescence lifetime of / AlOOH-3 indicate that the separation ability of photogenerated electrons and holes is enhanced by introducing Ni species into Au / AlOOH. Specifically, AuNi-Ni... SACThe lowest fluorescence intensity of / AlOOH-2 indicates that it exhibits the best effect in separating photogenerated carriers. To further investigate the kinetic characteristics of photoinduced carriers in the photocatalyst, time-resolved photoluminescence spectroscopy (TRPL) was used to study the fluorescence decay lifetime (τ) of photogenerated carriers. Figure 7 b shows the time-resolved photoluminescence spectra of all catalyst samples and the corresponding average carrier lifetimes. The Ni / AlOOH, Au / AlOOH, and AuNi-Ni ratios were calculated using second-order fitting. SAC / AlOOH-1、AuNi-Ni SAC / AlOOH-2 and AuNi-Ni SAC The average fluorescence decay lifetime of AlOOH-3 (τ) Ave The ns values ​​are 3.43, 4.14, 4.65, 4.71, and 4.27 ns, respectively. Among them, AuNi-Ni... SAC The average fluorescence decay lifetime of / AlOOH was higher than that of Au / AlOOH and Ni / AlOOH, indicating that the introduction of Ni species increased the lifetime, and AuNi-Ni SAC The / AlOOH-2 group exhibits the longest fluorescence lifetime. The increased lifetime τ enhances their likelihood of participating in photocatalytic reactions before recombination. This further demonstrates the contribution of Ni sites to improving charge separation efficiency, consistent with the activity trend. Therefore, the above analysis shows that the decrease in PL intensity and the increase in fluorescence lifetime provide strong evidence for Ni modification of the Au / AlOOH surface to accelerate electron transfer and suppress carrier recombination.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a single-atom Ni-modified AuNi alloy catalyst, characterized in that, The method comprises the following steps: Step 1, adding AlOOH carrier into Au nanoparticle solution, and sequentially performing ultrasonic treatment and mechanical stirring to make the Au nanoparticles and the AlOOH carrier self-assemble under electrostatic interaction, and then collecting the precipitate by centrifugal water washing; freezing and drying the obtained precipitate, and then performing annealing treatment to obtain Au nanoparticle loaded AlOOH composite material, denoted as Au / AlOOH; the particle size of the Au nanoparticles is 4-12 nm; Step 2, adding the Au / AlOOH composite material obtained in step 1 into deionized water and uniformly dispersing by ultrasonic treatment, and then adding Ni salt solution and methanol under vigorous stirring to obtain a suspension; performing ultraviolet light irradiation on the suspension in an inert gas atmosphere to reduce the Ni salt by the electrons generated by the Au nanoparticles and the AlOOH under light excitation; after the light irradiation, collecting the precipitate by centrifugal water washing and drying to obtain a single-atom Ni modified AuNi alloy photocatalyst; the concentration of the Ni salt solution is set to 10 g / L, and the amount ratio of the Au / AlOOH composite material, the deionized water, the Ni salt solution and the methanol is 1.0 g: 50-150 mL: 10-100 mL: 30-100 mL.

2. The production method according to claim 1, characterized by, In step 1, the concentration of the Au nanoparticle solution is 0.1-1 mM, and the amount ratio of the AlOOH carrier to the Au nanoparticle solution is 0.1-2.5 g / 103 mL.

3. The preparation method according to claim 1, characterized in that, In step 2, the Ni salt is selected from any one of Ni(NO3)2, NiCl2, NiSO4 and Ni(acac)2.

4. The production method according to claim 1, characterized by, In step 2, the wavelength of the ultraviolet light irradiation is 250-350 nm, and the irradiation time is 60-300 minutes.

5. A single-atom Ni modified AuNi alloy catalyst prepared by the preparation method in any one of claims 1-4.

6. The monatomic Ni-modified AuNi alloy catalyst according to claim 5, characterized in that: The catalyst comprises an AlOOH carrier and a metal active component loaded on the AlOOH carrier, and the metal active component is composed of AuNi nano-alloy particles and single-atom Ni.

7. The monatomic Ni modified AuNi alloy catalyst according to claim 6, characterized in that: The particle size of the AuNi nano-alloy particles is 5-15 nm.

8. Use of the single-atom Ni-modified AuNi alloy catalyst of claim 5, 6 or 7, characterized in that: The catalyst is used for photocatalytic CO2 reduction reaction to convert CO2 into CH4. The catalyst is used for photocatalytic CO2 reduction reaction to convert CO2 into CH4.

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