Chiral gold nanoparticles for alkaline water electrolysis oxygen evolution reaction catalyst and synthesis method and application thereof

Abstract

The present invention discloses chiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis, as well as their synthesis method and application. Chiral multi-branched gold nanoparticles, including L-type gold nanobranched particles and D-type gold nanobranched particles, are synthesized and further used to catalyze the oxygen evolution reaction. During the synthesis process, the chirality of the sample can be controlled by regulating the concentration of the chiral ligand, as reflected by the intensity of the circular dichroism signal. Compared with the prior art, the preparation method of the present invention is simple, has low manufacturing costs, and exhibits superior catalytic performance in the oxygen evolution reaction. The L-type gold nanobranched particles in the samples of the present invention exhibit far superior oxygen evolution reaction performance compared to the D-type gold nanobranched particles. At a current density of 10 mA / cm², the L-type gold nanobranched particles reach 355.1 and 449.7 mV, respectively, with a Tafel slope of 61.72 mV / decade. They maintain stable performance for 24 hours at a current density of 10 mA / cm², demonstrating excellent stability.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to chiral gold nanoparticles used as catalysts for oxygen evolution reaction in alkaline water electrolysis, as well as a synthesis method and application thereof. Background Art

[0002] Electrochemical water splitting is currently a highly researched area due to the enormous potential of hydrogen as an ideal zero-carbon fuel. The rate-determining step in water splitting is the oxygen evolution reaction (OER), which involves the transfer of four electrons and the formation of complex intermediates (including peroxides and superoxides), rather than the two-electron transfer process of the hydrogen evolution reaction (HER). Therefore, the synthesis of efficient OER catalysts is of great significance for improving selectivity, suppressing byproduct formation, and reducing overpotential energy losses during the electrochemical reaction.

[0003] The importance of hydrogen energy lies in its potential as a clean and sustainable fuel source, providing a pathway to mitigate climate change and reduce dependence on fossil fuels. Electrochemical catalytic water splitting is a key process for hydrogen production and holds great promise in this regard. Specifically, the rate-determining step of water splitting, the oxygen evolution reaction (OER), involves four electron transfers and the formation of complex intermediates such as peroxides and superoxides. Therefore, the synthesis of efficient OER catalysts is of great significance for improving selectivity, suppressing by-product formation, and simultaneously reducing overpotential energy losses during the electrochemical reaction.

[0004] CN104625086A discloses a method for preparing gold nanotriangular sheets, gold nanodiscs, and gold nanohexagonal sheets. The method for preparing the gold nanotriangular sheets comprises: first preparing a nanogold seed solution using an aqueous sodium citrate solution, an aqueous tetrachloroauric acid solution, and an aqueous sodium borohydride solution; then preparing a gold nanotriangular sheet solution using the prepared seed solution and an aqueous hexadecyltrimethylammonium bromide solution, an aqueous tetrachloroauric acid solution, an aqueous potassium iodide or sodium iodide solution, an aqueous sodium hydroxide solution, and an aqueous ascorbic acid solution; and discarding the supernatant to obtain the gold nanotriangular sheet. However, this method is difficult to synthesize, has many synthesis steps, and requires very precise control of the conditions and details. In addition, the synthesized gold nanotriangular sheet is difficult to completely separate from the reactants, so the gold nanotriangular sheet is not convenient for long-term storage (more than three months), otherwise it may deteriorate.

[0005] Therefore, there is an urgent need for a method for preparing chiral gold nanoparticles with a simple synthesis method to prepare chiral gold nanoparticles with excellent catalytic performance that can be used for oxygen evolution reaction. Summary of the Invention

[0006] In response to the differences in the prior art, the present invention aims to provide chiral gold nanoparticles, their synthesis methods, and applications for use as catalysts for the oxygen evolution reaction in alkaline water electrolysis. The present invention combines the structural design of nanomaterials with chiral properties to propose a novel catalytic strategy for the oxygen evolution reaction. By enhancing electron transport and spin selectivity, efficient catalysis of the oxygen evolution reaction is achieved, providing a new approach to the design of nanocatalysts. The present invention is an elemental noble metal chiral catalyst for the oxygen evolution reaction, namely, chiral gold dendritic triangular nanoplates. The catalyst exhibits an extremely high chiral optical signal (100-150 mdeg) in circular dichroism (CD) spectroscopy measurements. L-type and D-type chiral gold nano-branched triangular nanoplates exhibit significant performance differences in oxygen evolution reaction catalysis, with the L-type gold nano-branched triangular nanoplates even performing as well as commercial catalysts.

[0007] The present invention is achieved through the following technical solutions:

[0008] The first object of the present invention is to provide a method for synthesizing chiral gold nanoparticles for use as a catalyst for oxygen evolution reaction in alkaline water electrolysis, the method comprising the following steps:

[0009] (1) adding tetrachloroauric acid trihydrate and trisodium citrate hydrate to water, mixing the mixture, adding the mixture to water, then adding ice-cold sodium borohydride solution under stirring, heating the solution in a water bath after stirring, and then storing the gold seed solution at low temperature;

[0010] (2) adding the gold seed solution obtained in step (1) to a mixed solution A containing cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring and mixing until uniform, taking the mixed solution, adding it to a mixed solution B containing cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring and mixing until uniform, and then introducing the entire solution into a mixed solution C consisting of cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring the solution, then heating it in a water bath, centrifuging the product, removing the supernatant, and storing the substrate in the cetyltrimethylammonium bromide solution to obtain a solution D;

[0011] (3) Take water, add cetyltrimethylammonium bromide, tetrachloroauric acid and ascorbic acid in sequence, then stir, inject cysteine ​​solution into the solution to form a gold nanotriangle, stir for 1 to 2 minutes, then take solution D obtained in step (2) and add it to the mixed solution, stir, and then stand in a water bath to obtain a chiral gold nanoparticle dispersion, centrifuge the obtained chiral gold nanoparticle dispersion to remove unreacted reagents, remove the supernatant, and redisperse it in cetyltrimethylammonium bromide solution to obtain chiral gold nanoparticles.

[0012] Furthermore, the gold seed solution obtained in step (1) is a solution containing gold seeds, and the average particle size of the gold seeds in the gold seed solution is 30 nanometers to 60 nanometers.

[0013] Furthermore, the nanoparticles in the solution D obtained in step (2) are mostly triangular, with a small portion being pentagonal or hexagonal, and the average particle size of the nanoparticles in the solution D is 60 nm to 120 nm.

[0014] Furthermore, in step (3), when the cysteine ​​in the cysteine ​​solution is L-cysteine, the chiral gold nanoparticles formed are L-type gold nanobranched particles, and the L-type gold nanobranched triangles are snowflake-shaped, with the branches twisted in a clockwise direction and an average particle size of 400 to 600 nanometers.

[0015] Furthermore, in step (3), when the cysteine ​​in the cysteine ​​solution is D-type cysteine, the chiral gold nanoparticles formed are D-type gold nanobranched particles, and the D-type gold nanobranched triangles are snowflake-shaped, with the branches twisted counterclockwise, and the average particle size is 400 to 600 nanometers.

[0016] Furthermore, the chiral gold nanoparticles obtained in step (3) are chiral gold nanoparticles capable of detecting chiral optical signals, and when the absorption is around 0.5 to 1.5, the circular dichroism signal is between 100 and 150 mdeg.

[0017] Furthermore, the main crystal face of the chiral gold nanoparticles obtained in step (3) exposed in X-ray diffraction characterization is a gold (1 1 1) crystal face. Furthermore, the synthesis method specifically includes the following steps:

[0018] (1) 0.032 g of tetrachloroauric acid trihydrate and 0.0294 g of trisodium citrate hydrate were added to 20 mL of water, mixed, and 2 mL of the solution was added to 36.0 mL of water. Then, ice-cold sodium borohydride solution (0.1 M, 1.0 mL) was added under magnetic stirring. The temperature of the sodium borohydride solution was 0.5°C. After stirring for 2 minutes, the solution was placed in a water bath at 30°C for 4 hours, and then placed in a refrigerator at 0-2°C to store the gold seed solution.

[0019] (2) 0.5 mL to 2 mL of gold seed solution was added to a mixed solution A containing cetyltrimethylammonium bromide (0.05-1 M, 9 mL), tetrachloroauric acid (0.01 M, 0.25 mL), sodium hydroxide (0.1 M, 0.05 mL), potassium iodide (0.01 M, 0.05 mL) and ascorbic acid (0.1-0.2 M, 0.05 mL). After magnetic stirring to mix well, 1 mL of the solution was taken and added to a mixed solution A containing cetyltrimethylammonium bromide (0.05-1 M, 9 mL), tetrachloroauric acid (0.01 M, 0.25 mL), sodium hydroxide (0.1 M, 0.05 mL). A mixture of 100 mL of 1 M sodium hydroxide (0.01 M, 0.05 mL), potassium iodide (0.01 M, 0.05 mL), and ascorbic acid (0.1-0.2 M, 0.05 mL) was added to a mixed solution B containing 2 M sodium hydroxide (0.05-1 M, 90 mL), tetrachloroauric acid (0.01 M, 2.5 mL), sodium hydroxide (0.1 M, 0.5 mL), potassium iodide (0.01 M, 0.5 mL), and ascorbic acid (0.1-0.2 M, 0.5 mL). The solution was magnetically stirred for 5 minutes and then incubated in a 30°C water bath for 24 hours. After 24 hours, the product was separated by centrifugation at 4000-5000 rpm for 5 minutes. The supernatant was removed and the substrate was stored in 100 mL of a 1 mM solution of cetyltrimethylammonium bromide to obtain solution D.

[0020] (3) Take 34.77 mL of deionized water, add cetyltrimethylammonium bromide (8 mL, 10 mmol), tetrachloroauric acid (2 mL, 10 mM) and ascorbic acid (5 mL, 40 mM) in sequence, then stir at a speed of 50-100 rpm for 1-2 minutes, inject 3 μL of 0.5-1 mM cysteine ​​(L-cysteine ​​or D-cysteine) solution into the solution to form a gold nanobranched triangle, stir at a speed of 50-100 rpm for 1-2 minutes, then take 300-600 μL of solution D obtained in step (2) and add it to the mixed solution, and stir for 30 seconds, then let it stand in a water bath at 30°C for 1 hour, centrifuge the obtained chiral gold nanoparticle dispersion at 2500 rpm for 5 minutes to remove unreacted reagents, remove the supernatant, and redisperse it in 1 mM 10 mL cetyltrimethylammonium bromide solution to obtain chiral gold nanoparticles, which are stored at room temperature.

[0021] Furthermore, in step (3), 3 μL of 0.5-1 mM cysteine ​​(L-cysteine ​​or D-cysteine) solution is injected into the solution to form an L-type gold nanobranched triangle (L-type chiral gold nanoparticles are subsequently obtained, and the L-type chiral gold nanoparticles are L-type gold nanobranched particles) or a D-type gold nanobranched triangle (D-type chiral gold nanoparticles are subsequently obtained, and the D-type chiral gold nanoparticles are D-type gold nanobranched particles), and stirred at a speed of 50-100 rpm for 1-2 minutes (for achiral gold nanoconcave triangles, cysteine ​​is not added in this step, and achiral gold nanoparticles are subsequently obtained, and the achiral gold nanoparticles are achiral gold nanoconcave particles).

[0022] Furthermore, the L-type gold nanoparticles and D-type gold nanoparticles obtained in step (3) are snowflake-shaped, with branches twisting in clockwise and counterclockwise directions, respectively, and have an average particle size of 400 to 600 nanometers. The achiral gold nanoparticles with concave shapes are polygonal and flat, with no fixed twisting direction and an average particle size of 300 to 500 nanometers.

[0023] Furthermore, the L-shaped gold nanobranched triangles and the D-shaped gold nanobranched triangles obtained in step (3) can detect chiral optical signals. When the absorption is about 0.5 to 1.5, the circular dichroism spectrum signal is 100 to 150 mdeg. However, the achiral gold nanoconcave triangle nanoparticles have no obvious chiral optical signal. When the absorption is about 0.5 to 1.5, the circular dichroism spectrum is 0 to 20 mdeg.

[0024] Furthermore, the three chiral and achiral nanoparticles obtained in step (3): L-type gold nanobranched particles, D-type gold nanobranched particles, and achiral gold nanoconcave particles have the main crystal plane exposed in X-ray diffraction characterization as the gold (1 11) crystal plane.

[0025] Furthermore, the chiral gold nanoparticles obtained showed good catalytic performance in oxygen evolution reaction. 7-8 mg of the three chiral gold nanoparticles or achiral gold nanoparticles were loaded onto nickel foam 1×1 cm 2 Electrochemical measurements were performed at room temperature in a 1M potassium hydroxide (pH 14) solution using a perfluorosulfonic acid-polytetrafluoroethylene copolymer as a binder on a square area. Scanning at a scan rate of 5 mV / s and a current density of 10 mA / cm², the overpotential of the L-type chiral gold nanoparticles was 355.7 mV, even lower than that of a control drop-casted with an equal amount of commercial ruthenium dioxide catalyst (387.7 mV), as well as D-type chiral gold nanoparticles (449.1 mV) and achiral gold nanoparticles (455.3 mV).

[0026] Furthermore, the resulting chiral gold nanoparticles exhibited good catalytic performance in the oxygen evolution reaction. The Tafel slope of the L-type chiral gold nanoparticles at 10 mA / cm² was 61.72 mV / decade, significantly lower than the 136.76 mV / decade of the control group in which an equal amount of commercial catalyst ruthenium dioxide was drop-cast. The Tafel slopes of the D-type chiral gold nanoparticles and the achiral gold nanoparticles were 149.4 mV / decade and 228.0 mV / decade, respectively. The Tafel slope of the D-type chiral gold nanoparticles was not significantly different from that of ruthenium dioxide. The Tafel slope is the rate of change of the overpotential with the logarithm of the current density, which reveals the exchange current density and reaction kinetics of the electrochemical reaction of a specific catalyst.

[0027] The second object of the present invention is to provide a chiral gold nanoparticle, which is prepared by a chiral gold nanoparticle synthesis method for a catalyst for oxygen evolution reaction in alkaline water electrolysis.

[0028] The third object of the present invention is to provide an application of chiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis. The chiral gold nanoparticles are prepared using a method for synthesizing chiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis, and the chiral gold nanoparticles are used as catalysts for oxygen evolution reaction in alkaline electrolytes.

[0029] Furthermore, at a current density of 10 mA per square centimeter, the overpotential of the chiral gold nanoparticles is 355.7 mV to 449.1 mV.

[0030] Furthermore, the Tafel slope of the chiral gold nanoparticles at 10 milliamperes per square centimeter is 61.72 millivolts per decade to 149.4 millivolts per decade.

[0031] The technical concept of the present invention is as follows:

[0032] Among chiral nanomaterials, gold nanoparticles (GNPs) have garnered the most attention. Recently, chiral gold nanoparticles, characterized by strong optical activity and high circular dichroism values, have been extensively studied. However, they have rarely been used as chiral catalysts for the oxygen evolution reaction (OER), making them highly researchable. Gold, a noble metal, exhibits excellent OER performance, possesses suitable adsorption and desorption energies (favoring smooth OER catalysis), and exhibits high stability. Gold's strong chirality enables its high spin polarizability. Therefore, we hypothesize that GNPs could serve as ideal chiral catalysts for electrocatalytic water splitting. Their well-defined lattice structure and excellent electrical conductivity make them promising candidates. The surface properties of GNPs can be easily manipulated by varying their morphology, size, crystal structure, and surface modification, effectively tuning and optimizing their catalytic performance. Furthermore, when subjected to an electric field, which distorts the electron cloud density, they exhibit less lattice irregularities caused by heterojunctions, doping, or vacancies, thereby facilitating better spin transfer. Furthermore, noble metal catalysts often exhibit high selectivity due to their empty d-orbitals, which facilitate bond formation with other radicals, as the reactivity of a catalyst is highly correlated with the proportion of d-electrons participating in coordination. Noble metals possess 5d or 7d orbitals, which have larger radii than the 3d orbitals of transition catalysts, allowing them to utilize a higher proportion of d-orbital electrons in coordination. Furthermore, the stability of gold allows for its repeated use, making it a practical and sustainable choice for electrochemical water splitting applications.

[0033] Therefore, the present invention provides a chiral gold nanoparticle and a preparation method and application thereof.

[0034] The present invention uses cysteine ​​as an inducer to synthesize chiral gold nano-branched triangles through a seed-mediated site-selective chiral growth system. First, gold triangular nanoplates (gold nano-triangles) are synthesized by gold seed crystals in the presence of potassium iodide. The prepared gold nano-triangles have a uniform triangular plate structure with exposed {111} plane facets and an average side length of 172±24nm. The gold nano-triangles are introduced into a growth solution of tetrachloroauric acid, ascorbic acid, hexadecyltrimethylammonium bromide and chiral molecules to initiate the growth of the chiral gold nano-triangles. L / D-cysteine ​​is used as a chiral inducer to interact enantioselectively with the gold surface and drive the formation of a propeller structure with highly twisted chiral characteristics. Growing branches or twigs along a specific direction on a gold nanotriangle results in the formation of anisotropic chiral dendritic nanotriangles (L-type gold nanobranched triangles or D-type gold nanobranched triangles), which further yield anisotropic chiral dendritic nanoparticles (L-type gold nanobranched particles or D-type gold nanobranched particles). In contrast, achiral gold concave nanotriangles (achiral gold nanoconcave triangles) were synthesized in the absence of cysteine, promoting preferential conformal growth of gold on the side edge facets, resulting in a lack of a specific growth direction and further yielding achiral gold concave nanoparticles (achiral gold nanoconcave particles).

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The present invention's innovations in nanomaterial preparation technology, particularly its application in the electrocatalytic oxygen evolution reaction (EOR), demonstrate unique advantages and potential. The following is a detailed explanation of the key points of the present invention:

[0037] (1) Branched structure: By carefully controlling the synthesis conditions, gold nanoparticles with a branched morphology are prepared. This structure not only increases the specific surface area of ​​the material and provides more catalytic active sites, but also its multiple tips can significantly enhance the local electric field effect (tip effect), helping to accelerate the transmission of electrons on the catalyst surface, thereby improving the catalytic efficiency of the oxygen evolution reaction.

[0038] (2) Nanosize control: Precisely controlling the size and shape of gold nanoparticles is key to achieving efficient catalysis. The nanoscale size gives gold particles a higher surface energy, enhancing their interaction with reactants. At the same time, specific shape design (such as branched shape) further optimizes catalytic performance.

[0039] (3) Strong chiral signal: The synthesized gold nanoparticles exhibit strong chiral properties, which are achieved through a specific synthesis method. Chiral materials exhibit unique asymmetry in optical and electrical properties and can affect the spin state of electrons.

[0040] (4) Chirality-induced spin selectivity: The chirality-induced spin selectivity of chiral gold nanoparticles is utilized to act as a spin filter in the catalytic process of oxygen evolution reaction. This effect can selectively transmit electrons with specific spin states, thereby inhibiting the formation of byproduct hydrogen peroxide and promoting the formation of target product oxygen, thereby improving the selectivity and efficiency of the oxygen evolution reaction.

[0041] This study combines the structural design of nanomaterials with their chiral properties to propose a novel catalytic strategy for the oxygen evolution reaction (OER). By enhancing electron transport and spin selectivity, it achieves highly efficient OER catalysis, providing new insights into the design of nanocatalysts.

[0042] The preparation method of the present invention is simple, the manufacturing cost is low, and the catalytic performance of the oxygen evolution reaction is excellent. The chiral catalyst utilizes the chirality-induced spin selectivity effect to suppress the generation of the byproduct hydrogen peroxide in the oxygen evolution reaction, thereby promoting the occurrence of the oxygen evolution reaction. Previously reported chiral catalysts did not show performance differences between L-type and D-type chirality when catalyzing the oxygen evolution reaction, while the oxygen evolution reaction performance of the L-type gold nanobranched particles in the sample of the present invention is far superior to that of the D-type gold nanobranched particles, and is comparable to the performance of the commercial oxygen evolution reaction catalyst ruthenium dioxide. At a current density of 10 milliamperes per square centimeter, the overpotentials of the L-type gold nanobranched particles and the D-type gold nanobranched particles are 355.1 and 449.7 millivolts, respectively, and the Tafel slopes are 61.72 and 149.4 millivolts per decade. Stability tests show that the catalyst of the present invention can maintain stable performance for 24 hours at a current density of 10 milliamperes per square centimeter, and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The figure shows the comparison of circular dichroism signal intensities prepared at different L-cysteine ​​concentrations in Example 1 of the present invention.

[0044] Figure 2 This is a transmission electron microscope (TEM) image of the L-shaped gold nano-branched particles prepared in Example 2 of the present invention.

[0045] Figure 3 This is a transmission electron microscope (TEM) image of the D-type gold nanobranched particles prepared in Example 2 of the present invention.

[0046] Figure 4 This is a transmission electron microscope (TEM) image of the achiral gold nanoconcave particles prepared in Example 2 of the present invention.

[0047] Figure 5 Circular dichroism signal diagram of three nanoparticles prepared in Example 2 of the present invention.

[0048] Figure 6These are X-ray diffraction patterns of the three nanoparticles prepared in Example 2 of the present invention.

[0049] Figure 7 A standard three-electrode electrolytic cell for electrochemical water splitting measurements.

[0050] Figure 8 This is the linear sweep voltammetry test result in Example 3 of the present invention.

[0051] Figure 9 This is the electrochemical impedance spectroscopy test result in Example 3 of the present invention.

[0052] Figure 10 These are the Tafel slope and overpotential at a current density of 10 mA per square centimeter measured in Example 3 of the present invention.

[0053] Figure 11 To demonstrate the stability of the L-type sample in Example 3 of the present invention, cyclic voltammetry was used to scan 1000 times, and there was almost no significant change in performance.

[0054] Figure 12 To demonstrate the stability of the L-type sample in Example 3 of the present invention, the performance showed almost no significant change when the sample was run at a current density of 10 mA / cm2 for 24 hours using chronopotentiometry.

[0055] Figure 13 Schematic diagram of nanoparticles in solution D in Example 1 of the present invention.

[0056] Figure 14 3 are scanning electron microscope (SEM) images of the L-shaped gold nano-branched particles prepared in Example 2 of the present invention, wherein (a) and (b) are SEM images at different scales.

[0057] Figure 15 3 are scanning electron microscope (SEM) images of the D-type gold nano-branched particles prepared in Example 2 of the present invention, wherein (a) and (b) are SEM images at different scales.

[0058] Figure 16 These are scanning electron microscope (SEM) images of the achiral gold nanoconcave particles prepared in Example 2 of the present invention, wherein (a) and (b) are SEM images at different scales. DETAILED DESCRIPTION

[0059] The present invention is described in detail below with reference to specific embodiments, but is by no means intended to limit the present invention. Any features, such as preparation methods, materials, structures, or composition ratios, that are not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0060] The following examples will help those skilled in the art further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several variations and improvements without departing from the scope of the present invention. These variations and improvements are all within the scope of protection of the present invention.

[0061] The practice of the present invention can employ conventional techniques of chemistry within the skill of the art. In the following examples, efforts have been made to ensure accuracy with respect to the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be accounted for.

[0062] The present invention synthesizes chiral multi-branched gold nanoparticles, L-type gold nano-branched particles, D-type gold nano-branched particles, and corresponding achiral catalyst achiral gold nano-concave particles for catalyzing oxygen evolution reaction. During the synthesis process, the chirality of the sample can be regulated by regulating the concentration of the chiral ligand, which can be reflected by the intensity of the circular dichroism signal. The preparation method of the present invention is simple, the manufacturing cost is low, and the catalytic performance of the oxygen evolution reaction is excellent. The chiral catalyst utilizes the chirality-induced spin selectivity effect to inhibit the formation of the by-product hydrogen peroxide in the oxygen evolution reaction, thereby promoting the occurrence of the oxygen evolution reaction. Previously reported chiral catalysts did not show performance differences between L-type and D-type chirality when catalyzing the oxygen evolution reaction, while the oxygen evolution reaction performance of the L-type gold nano-branched particles in the sample of the present invention is far better than that of the D-type gold nano-branched particles, and is comparable to the performance of the commercial oxygen evolution reaction catalyst ruthenium dioxide. At a current density of 10 mA / cm², the overpotentials of the L-type and D-type gold nanoparticles were 355.1 and 449.7 mV, respectively, with Tafel slopes of 61.72 and 149.4 mV / decade, respectively. Stability tests showed that the catalyst maintained stable performance for 24 hours at a current density of 10 mA / cm², demonstrating excellent stability.

[0063] In this embodiment, all reagents used are commercially available reagents.

[0064] Example 1

[0065] This embodiment provides a method for synthesizing chiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis, specifically L-shaped chiral gold nanoparticles. The synthesis method comprises the following steps:

[0066] (1) 0.032 g of tetrachloroauric acid trihydrate and 0.0294 g of trisodium citrate hydrate were added to 20 mL of water, mixed, and 2 mL of the solution was added to 36.0 mL of water. Then, ice-cold sodium borohydride solution (0.1 M, 1.0 mL) was added under magnetic stirring. The temperature of the sodium borohydride solution was 0.5°C. After stirring for 2 minutes, the solution was placed in a water bath at 30°C for 4 hours, and then placed in a refrigerator at 0-2°C to store the gold seed solution.

[0067] (2) 1 ml of the gold seed solution was added to a mixed solution A containing a cetyltrimethylammonium bromide solution (1 M, 9 mL), a tetrachloroauric acid aqueous solution (0.01 M, 0.25 mL), a sodium hydroxide aqueous solution (0.1 M, 0.05 mL), a potassium iodide aqueous solution (0.01 M, 0.05 mL) and an ascorbic acid solution (0.1 M, 0.05 mL). After being mixed evenly by magnetic stirring, 1 mL of the solution was taken and added to a mixed solution containing a cetyltrimethylammonium bromide solution (1 M, 9 mL), a tetrachloroauric acid aqueous solution (0.01 M, 0.25 mL), a sodium hydroxide solution (0.1 M, 0.05 mL). The mixture was then added to a mixed solution B consisting of 1 M cetyltrimethylammonium bromide solution (90 mL), a tetrachloroauric acid aqueous solution (0.01 M, 2.5 mL), a sodium hydroxide aqueous solution (0.1 M, 0.5 mL), a potassium iodide aqueous solution (0.01 M, 0.5 mL), and an ascorbic acid solution (0.1 M, 0.5 mL). After magnetic stirring to mix thoroughly, the entire solution was introduced into a mixed solution C consisting of 1 M cetyltrimethylammonium bromide solution (90 mL), a tetrachloroauric acid aqueous solution (0.01 M, 2.5 mL), a sodium hydroxide aqueous solution (0.1 M, 0.5 mL), a potassium iodide aqueous solution (0.01 M, 0.5 mL), and an ascorbic acid solution (0.1 M, 0.5 mL). The solution was magnetically stirred for 5 minutes and then incubated in a 30°C water bath for 24 hours. After 24 hours, the product was separated by centrifugation at 4000-5000 rpm for 5 minutes. The supernatant was removed and the substrate was stored in 1 M cetyltrimethylammonium bromide solution (100 mL) to obtain solution D.

[0068] (3) Take 34.77 mL of deionized water, add cetyltrimethylammonium bromide solution (8 mL, 10 mmol), tetrachloroauric acid aqueous solution (2 mL, 10 mM) and ascorbic acid solution (5 mL, 40 mM) in sequence, and then stir at a speed of 50-100 rpm for 1-2 minutes, inject 3 μL of 1 mM cysteine ​​(cysteine ​​is selected from L-type cysteine ​​or D-type cysteine, L-type cysteine ​​in this embodiment) solution into the solution to form an L-type gold nanobranched triangle or a D-type gold nanobranched triangle, and stir at a speed of 50-100 rpm for 1-2 minutes (for achiral gold nanoconcave triangles, cysteine ​​is not added in this step). Then, 300 to 600 μL of solution D obtained in step (2) was added to the mixed solution and stirred for 30 seconds. The mixture was then allowed to stand in a water bath at 30° C. for 1 hour. The resulting chiral gold nanoparticle dispersion was centrifuged at 2500 rpm for 5 minutes to remove unreacted reagents. After removing the supernatant, the mixture was redispersed in 10 mL of 1 mM hexadecyltrimethylammonium bromide solution to obtain chiral gold nanoparticles, which were then stored at room temperature.

[0069] The L-cysteine ​​solution (L-cysteine ​​aqueous solution) was prepared as follows: 0.0404 g, 0.0505 g, and 0.0606 g of L-cysteine ​​were added to 20 mL of deionized water, respectively, and mixed evenly. Then, 1 mL of the prepared L-cysteine ​​aqueous solution was added to 11.5 mL of deionized water, and mixed evenly to obtain 2 / 3 mM, 5 / 6 mM, and 1 mM L-cysteine ​​aqueous solutions, respectively.

[0070] When preparing the chiral gold nanoparticles in step (3), three groups of solutions were prepared. 34.77 mL of deionized water was added to each group. Hexadecyltrimethylammonium bromide solution (8 mL, 10 mmol), tetrachloroauric acid aqueous solution (2 mL, 10 mM), and ascorbic acid solution (5 mL, 40 mM) were added in sequence. The mixture was then stirred at 50-100 rpm for 1-2 minutes. 3 μL of 2 / 3 mM, 5 / 6 mM, and 1 mM L-cysteine ​​aqueous solutions were injected into one of the groups of solutions. The mixture was stirred at 50-100 rpm for 2 minutes. 300-600 μL of the solution obtained in step (2) was then added to the mixed solution and stirred for 30 seconds. The mixture was then allowed to stand in a 30°C water bath for 1 hour. The obtained chiral gold nanoparticle dispersion was centrifuged at 2500 rpm for 5 minutes to remove unreacted reagents. After removing the supernatant, it was redispersed in 10 mL of 1 mM hexadecyltrimethylammonium bromide solution and stored at room temperature to obtain chiral gold nanoparticles. The obtained sample circular dichroism signal intensities were 70 mdeg, 100 mdeg, and 200 mdeg, respectively. Figure 1 shown.

[0071] Example 2

[0072] This embodiment provides a method for synthesizing chiral gold nanoparticles / achiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis. The method is basically the same as the synthesis method in Example 1, except that: when preparing the chiral gold nanoparticles in (3), three groups of solutions are divided. 34.77 mL of deionized water is taken from each group. Hexadecyltrimethylammonium bromide solution (8 mL, 10 mmol), tetrachloroauric acid aqueous solution (2 mL, 10 mM), and ascorbic acid solution (5 mL, 40 mM) are added in sequence, and then stirred at a speed of 50-100 rpm for 1-2 minutes. 3 μL of 1 mM L-cysteine ​​solution and D-cysteine ​​solution are respectively injected into one group of solutions, while no cysteine ​​solution is added to the other group. Stirring is carried out at a speed of 50-100 rpm for 2 minutes. Then, 300-600 μL of solution D obtained in step (2) is added to the mixed solution and stirred for 30 seconds. Then, the solution is allowed to stand in a water bath at 30°C for 1 hour. The obtained chiral gold nanoparticle dispersion (no cysteine ​​solution is used to obtain an achiral gold nanoparticle dispersion) was centrifuged at 2500rpm for 5 minutes to remove unreacted reagents. After removing the supernatant, it was redispersed in 1mM 10mL cetyltrimethylammonium bromide solution and stored at room temperature to obtain chiral gold nanoparticles or achiral nanoparticles (adding 3μL 1mM L-type cysteine ​​solution to obtain L-type chiral gold nanoparticles, adding 3μL 1mM D-type cysteine ​​solution to obtain D-type chiral gold nanoparticles, and not adding cysteine ​​solution to obtain achiral gold nanoparticles). Transmission electron microscopy images of the three groups of samples (specifically, the transmission electron microscopy images are of the chiral gold nanoparticles / achiral gold nanoparticles after washing the cetyltrimethylammonium bromide) are shown in Figure 2. Figures 2 to 4 , L-type chiral gold nanoparticles are L-type gold nanoparticles with branched shape, D-type chiral gold nanoparticles are D-type gold nanoparticles with branched shape, and achiral gold nanoparticles are achiral gold nanoparticles with concave shape. The circular dichroism signals are as follows: Figure 5 As shown, the obtained chiral nanoparticles, L-type gold nanobranched particles and D-type gold nanobranched particles, can detect chiral optical signals. When the absorption is around 0.5-1.5, the circular dichroism signal is between 100-150 mdeg (relative to the optical signal of the 1 mM L-cysteine ​​aqueous solution embodiment in Example 1, which is weaker due to the lower sample concentration during detection than in Example 1). However, the achiral gold nanoconcave triangle plate nanoparticles have no obvious chiral optical signal. When the absorption is around 0.5-1.5, the circular dichroism spectrum is between 0-20 mdeg.

[0073] The preparation method of D-cysteine ​​solution (D-cysteine ​​aqueous solution) is basically the same as the preparation method of L-cysteine ​​aqueous solution in Example 1: 0.0606 g of D-cysteine ​​is added to 20 mL of deionized water and mixed evenly. Then, 1 mL of the freshly prepared D-cysteine ​​aqueous solution is added to 11.5 mL of deionized water and mixed evenly to obtain a 1 mM D-cysteine ​​aqueous solution.

[0074] Example 3

[0075] The three chiral gold nanoparticles prepared in Example 2 were washed and then drop-casted onto nickel foam to prepare the working electrode. Perfluorosulfonic acid-polytetrafluoroethylene copolymer was used as a binder. An average of 7-8 mg of sample was dispersed in water and dropped to 1 cm 2 Nickel foam (1×3cm 2 ). Oxygen evolution reaction performance was tested using linear sweep voltammetry and electrochemical impedance spectroscopy. Figure 7 A standard three-electrode electrolytic cell for electrochemical water splitting measurements is shown. The reference electrode and counter electrode are mercury / mercuric oxide (1 M potassium hydroxide) and a carbon rod, respectively. Electrochemical studies were performed using 1 M potassium hydroxide (pH = 14) aqueous electrolyte. Linear sweep voltammetry, electrochemical impedance spectroscopy, overpotential, and Tafel slope are shown in Figure 1. Figure 8 、 9 , 10. In order to test the stability of L-type gold nanoparticles, cyclic voltammetry was performed 1000 times in the system described above, and the performance was almost unchanged, as shown in FIG. Figure 11 As shown; and the oxygen evolution reaction test was carried out at a current density of 10 mA per square centimeter for 24 hours using chronopotentiometry, and no significant change in potential was observed, as shown Figure 12 shown.

[0076] Control Example

[0077] In this comparative example, a commercial catalyst, ruthenium dioxide, was drop-cast onto nickel foam to prepare a working electrode, and the process of oxygen evolution reaction performance testing was the same as that in Example 3.

[0078] In summary, the gold seed solution obtained in step (1) is a solution containing gold seeds, and the average particle size of the gold seeds in the gold seed solution is 30 nm to 60 nm. The nanoparticles in the solution D obtained in step (2) include triangular particles, and the average particle size of the nanoparticles in the solution D is 60 nm to 120 nm (e.g. Figure 13 As shown). Figures 2-4 , 6, 14-16, by scanning electron microscopy ( Figures 14-16 ), transmission electron microscopy ( Figures 2-4 ) and X-ray diffraction ( Figure 6) The morphology and crystal structure of L / D-type gold nanoparticles and achiral gold nanoparticles were characterized. The gold atoms on the small facets on the side edges of the particles follow the island growth mode of chiral gold nanobranched particles, thereby inducing a unique site-selective growth pathway and geometry-dependent chirality. In contrast, achiral gold nanoparticles exhibit a uniform growth pattern of gold atoms along the {111} plane crystal plane of gold without any chiral distortion. Branches and twigs with clear edges and tips extending in a specific direction from the corners or sides of the triangular nanoplates appear. This phenomenon not only enhances the chirality of the chiral gold nanobranched particles, but also acts as a spike to attract charges due to the enhanced electric field at the tip. The L-type gold nanobranched particles and D-type gold nanobranched particles obtained in step (3) are snowflake-shaped, with branches twisted in the clockwise and counterclockwise directions, respectively, and the average particle size is 400 to 600 nanometers. The achiral gold nanoconcave particles are polygonal flat, with no fixed twisting direction, and the average particle size is 300 to 500 nanometers. Furthermore, high-resolution transmission electron microscopy images provided valuable insights into the chirality of the atomic lattice structure. Given that charge primarily accumulates at the dendrite tips during electrochemical measurements, the lattice structure of these tips was specifically investigated. L-type gold nanobranched particles exhibited a polycrystalline structure, with lattice spacings of 0.198 nm, 0.219 nm, and 0.237 nm observed at the dendrite tips. Similarly, D-type gold nanobranched particles displayed lattice spacings of 0.198 nm, 0.217 nm, and 0.239 nm, very similar to those of L-type gold nanobranched particles. However, the lattice spacings of achiral gold nanoconcave particles (0.201 nm, 0.219 nm, and 0.226 nm) deviated slightly from those of chiral gold nanobranched particles, with a smaller maximum lattice spacing and a larger minimum lattice spacing. This suggests that the chiral species exhibits lattice distortion, resulting in a decrease in the lattice spacing perpendicular to the distortion and an increase in the spacing parallel to the distortion.

[0079] X-ray diffraction patterns (XRD) were used to investigate whether lattice changes exist in chiral crystals. The main peak in the XRD patterns of all three species was (1 1 1), consistent with the results of high-resolution transmission electron microscopy. There were no significant differences in the XRD patterns between L-type and D-type gold nanobranched particles. Furthermore, the peaks for chiral and achiral crystals were nearly identical, indicating that chirality does not alter the type of crystal faces.

[0080] X-ray photoelectron spectroscopy was used to detect binding energy and valence states. The gold 4f 7 / 2 and 4f 5 / 2 peaks of L-type gold nanobranched particles are located at 83.62 and 87.3 eV, while those of D-type gold nanobranched particles are located at 83.66 and 87.33 eV. Therefore, there is almost no difference in the binding energy between L-type gold nanobranched particles and D-type gold nanobranched particles. However, compared with achiral gold nanoparticles (gold 4f 7 / 2 is 83.45 eV and gold 4f 5 / 2 is 87.12 eV), the binding energy of chiral gold nanoparticles is slightly shifted toward higher binding energy by about 0.15 eV. This suggests that the chiral distortion of the lattice may affect the charge distribution and lead to higher binding energy, which means that for chiral species, the core may have a stronger electron affinity and more stably bind to the surrounding electrons, which helps to regulate adsorption and desorption during catalytic reactions.

[0081] like Figure 10 As shown, the excellent oxygen evolution reaction activity of L-type gold nanobranched particles can be verified by their low overpotential and Tafel slope. When the current density is 10 mA per square centimeter, the overpotential of L-type gold nanobranched particles is 355.7 mV, which is even lower than the overpotential of commercial catalysts ruthenium dioxide (387.7 mV), D-type gold nanobranched particles (449.1 mV), and achiral gold nanoconcave particles (455.3 mV). The Tafel slope, that is, the rate of change of potential with the logarithm of current density, reveals the electrochemical exchange current and reaction kinetics of a specific catalyst. The Tafel slope of L-type gold nanobranched particles at 10 mA per square centimeter is 61.72 mV per decade, significantly lower than the 136.76 mV per decade of commercial catalysts. For D-type gold nanobranched particles and achiral gold nanoconcave particles, their Tafel slopes are 149.4 mV per decade and 228.0 mV per decade, respectively.

[0082] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned embodiments. The description of the embodiments is for the convenience of ordinary technicians in this technical field to understand and use the invention. It is obvious that those familiar with the technology in this field can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without having to go through creative work. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for synthesizing chiral gold nanoparticles for use as catalysts for oxygen evolution reaction in alkaline water electrolysis, characterized in that: The synthesis method comprises the following steps: (1) adding tetrachloroauric acid trihydrate and trisodium citrate hydrate to water, mixing the mixture, adding the mixture to water, then adding ice-cold sodium borohydride solution under stirring, heating the solution in a water bath after stirring, and then storing the gold seed solution at low temperature; (2) adding the gold seed solution obtained in step (1) to a mixed solution A containing cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring and mixing until uniform, taking the mixed solution, adding it to a mixed solution B containing cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring and mixing until uniform, and then introducing the entire solution into a mixed solution C consisting of cetyltrimethylammonium bromide, tetrachloroauric acid, sodium hydroxide, potassium iodide and ascorbic acid, stirring the solution, then heating it in a water bath, centrifuging the product, removing the supernatant, and storing the substrate in the cetyltrimethylammonium bromide solution to obtain a solution D; (3) Take water, add cetyltrimethylammonium bromide, tetrachloroauric acid and ascorbic acid in sequence, then stir, inject cysteine ​​solution into the solution to form a gold nanotriangle, stir for 1 to 2 minutes, then take solution D obtained in step (2) and add it to the mixed solution, stir, and then stand in a water bath to obtain a chiral gold nanoparticle dispersion, centrifuge the obtained chiral gold nanoparticle dispersion to remove unreacted reagents, remove the supernatant, and redisperse it in cetyltrimethylammonium bromide solution to obtain chiral gold nanoparticles.

2. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, wherein: The gold seed solution obtained in step (1) is a solution containing gold seeds, and the average particle size of the gold seeds in the gold seed solution is 30 nanometers to 60 nanometers.

3. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, wherein: The nanoparticles in the solution D obtained in step (2) are triangular particles, and the average particle size of the nanoparticles in the solution D is 60 nm to 120 nm.

4. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, wherein: In step (3), when the cysteine ​​in the cysteine ​​solution is L-cysteine, the chiral gold nanoparticles formed are L-type gold nanobranched particles, and the L-type gold nanobranched triangles are snowflake-shaped, with the branches twisted in a clockwise direction and an average particle size of 400 to 600 nanometers.

5. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, characterized in that: In step (3), when the cysteine ​​in the cysteine ​​solution is D-cysteine, the chiral gold nanoparticles formed are D-type gold nanobranched particles, and the D-type gold nanobranched triangles are snowflake-shaped, with the branches twisted counterclockwise, and the average particle size is 400 to 600 nanometers.

6. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, characterized in that: The chiral gold nanoparticles obtained in step (3) are chiral gold nanoparticles capable of detecting chiral optical signals, and when the absorption is about 0.5 to 1.5, the circular dichroism signal is 100 to 200 mdeg; The main crystal plane of the chiral gold nanoparticles obtained in step (3) exposed in X-ray diffraction characterization is the gold (11 1) crystal plane.

7. The method for synthesizing chiral gold nanoparticles for an alkaline water electrolysis oxygen evolution reaction catalyst according to claim 1, characterized in that: The synthetic method specifically comprises the following steps: (1) 0.0256-0.0384 g of tetrachloroauric acid trihydrate and 0.02352-0.03528 g of trisodium citrate hydrate were added to 20 mL of water, mixed, and 2 mL of the solution was added to 36.0 mL of water. Then, 1.0 mL of 0.1 M ice-cold sodium borohydride solution was added under magnetic stirring. The temperature of the sodium borohydride solution was 0.5° C. After stirring for 2 minutes, the solution was placed in a water bath at 30° C. for 4 hours, and then placed in a refrigerator at 0-2° C. to store the gold seed solution. (2) 0.5 mL to 2 mL of gold seed solution was added to a mixed solution A containing 9 mL of 0.05-1 M hexadecyltrimethylammonium bromide, 0.25 mL of 0.01 M tetrachloroauric acid, 0.05 mL of 0.1 M sodium hydroxide, 0.05 mL of 0.01 M potassium iodide and 0.05 mL of 0.1-0.2 M ascorbic acid. After magnetic stirring to mix well, 1 mL of the solution was taken and added to 9 mL of 0.05-1 M hexadecyltrimethylammonium bromide, 0.25 mL of 0.01 M tetrachloroauric acid, 0.05 mL of 0.1 M sodium hydroxide, 0.05 mL of 0.01 M potassium iodide and 0.05 mL of 0.1-0.2 M ascorbic acid. Potassium iodide and 0.05 mL of 0.1-0.2 M ascorbic acid were mixed in a solution B by magnetic stirring, and then the entire solution was introduced into a mixed solution C consisting of 90 mL of 0.05-1 M cetyltrimethylammonium bromide, 2.5 mL of 0.01 M tetrachloroauric acid, 0.5 mL of 0.1 M sodium hydroxide, 0.5 mL of 0.01 M potassium iodide, and 0.5 mL of 0.1-0.2 M ascorbic acid. The solution was magnetically stirred for 5 minutes and then incubated in a water bath at 30° C. for 24 hours. After 24 hours, the product was centrifuged at 4000-5000 rpm for 5 minutes, the supernatant was removed, and the substrate was stored in 100 mL of a 1 mM cetyltrimethylammonium bromide solution to obtain a solution D. (3) Take 34.77 mL of deionized water, add 8 mL of 10 mmol hexadecyltrimethylammonium bromide, 2 mL of 10 mM tetrachloroauric acid and 5 mL of 40 mM ascorbic acid in sequence, then stir at a speed of 50-100 rpm for 1-2 minutes, inject 3 μL of 0.5-1 mM cysteine ​​solution into the solution to form a gold nanobranched triangle, stir at a speed of 50-100 rpm for 1-2 minutes, then take 300-600 μL of solution D obtained in step (2) and add it to the mixed solution, and stir for 30 seconds, then let it stand in a water bath at 30°C for 1 hour, centrifuge the obtained chiral gold nanoparticle dispersion at 2500 rpm for 5 minutes to remove unreacted reagents, remove the supernatant, and redisperse it in 1 mM 10 mL hexadecyltrimethylammonium bromide solution to obtain chiral gold nanoparticles, which are stored at room temperature.

8. A chiral gold nanoparticle for use as a catalyst for oxygen evolution in alkaline water electrolysis, characterized in that: The chiral gold nanoparticles are prepared by the synthesis method for the catalyst for the alkaline water electrolysis oxygen evolution reaction according to any one of claims 1 to 7.

9. An application of chiral gold nanoparticles prepared by the synthesis method according to any one of claims 1 to 7 as a catalyst for oxygen evolution reaction in alkaline water electrolysis, characterized in that: The chiral gold nanoparticles are used as catalysts for oxygen evolution reaction in an alkaline electrolyte.

10. The use according to claim 9, characterized in that At a current density of 10 mA per square centimeter, the overpotential of the chiral gold nanoparticles is 355.7 mV to 449.1 mV; The Tafel slope of the chiral gold nanoparticles at 10 mA / cm2 is 61.72 mV / decade to 149.4 mV / decade.

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