A ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate

Abstract

This invention discloses a ligand-free electrodeposition method for growing platinum nanowire arrays on a substrate, with lengths reaching up to approximately 10 μm. The method exhibits a wide deposition potential range of -0.5 V to -7 V. By adjusting the deposition time, the length of the platinum nanowires can be controlled on the substrate without a template or small molecule ligands. Furthermore, the density of the platinum nanowires can be controlled by varying the concentration of the silane coupling agent. Moreover, this synthesis can be extended to conductive substrates, allowing the platinum nanowire arrays to be directly used as working electrodes, providing significant application potential in fields such as electrocatalysis. This invention offers advantages such as simple process, mild reaction conditions, low cost, and the precise controllability, ease of operation, and environmental friendliness of electrodeposition for synthesizing nanomaterials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanomaterial synthesis, and relates to a ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate. BACKGROUND

[0002] One-dimensional platinum-based nanomaterials have wide application potential in catalysis, energy, electronics, biomedicine and other fields due to their unique structure and properties, including high aspect ratio, large specific surface area, fast electron transport and the like. However, the one-dimensional morphology makes the synthesis of platinum nanowires quite challenging. Because metal crystals usually have highly symmetrical lattices, they lack the inherent tendency of one-dimensional anisotropic growth. Therefore, the current methods for synthesizing platinum nanowires are mainly based on the use of templates and ligand-assisted growth, and the synthesis of relatively long platinum nanowires is usually realized in the templates. However, the assembly and subsequent removal of these templates are very complex and involve strict conditions and reagents. In addition, it is difficult to find suitable templates with the required diameter and length of the pore channel, and it is also difficult to completely remove the templates without affecting the integrity of the nanowires.

[0003] In addition, in the ligand-assisted synthesis of platinum nanowires, the most commonly used ligands are oleylamine and polyvinylpyrrolidone. However, from a traditional perspective, when the nanowires are used as catalysts, the ligand layer on the surface blocks the catalytically active sites. Moreover, platinum is difficult to grow in one dimension without the assistance of templates or ligands, which may be related to the inherent isotropic crystal growth behavior of platinum. Unlike other noble metals such as Au and Ag, the surface energy difference of different faces of Pt is greater than that of the corresponding surfaces of Au and Ag, so it is difficult to achieve morphological transformation by fine-tuning the reaction parameters.

[0004] Therefore, considering the side effects of ligands on nanocatalysis, various strategies have been developed to remove ligands, but in the process of removing ligands, the morphology and size of the nanowires are inevitably damaged. Therefore, it is still a great challenge to synthesize high-quality platinum nanowires under ligand-free conditions. SUMMARY

[0005] The present application aims to provide a ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate. The present application utilizes electrochemical deposition method, has a wide growth potential window (-0.5 V to -7 V), and can obtain platinum nanowire arrays of different lengths by adjusting the deposition time. The density of the platinum nanowire arrays can be controlled by changing the APTES concentration. In addition, the synthesis can be extended to conductive substrates, so that the platinum nanowire arrays can be directly used as working electrodes in subsequent applications, providing great application potential in the field of electrocatalysis. The present application has the advantages of simple process, mild reaction conditions, low cost, precise controllability, easy operation and environmental protection.

[0006] In order to solve the technical problems of the present application, the technical scheme is proposed: a ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate, comprising the following steps:

[0007] (1) First, the substrate is subjected to hydrophilic treatment by a plasma cleaning machine, and then subjected to amino treatment under acidic conditions using a solution of aminopropyltriethoxysilane (APTES);

[0008] (2) The substrate in step (1) is taken out to wash away the excess APTES solution and immersed in a platinum particle solution;

[0009] (3) The substrate in step (2) is taken out to wash away the excess platinum particle solution, and then an electrolyte is prepared;

[0010] (4) The electrodeposition uses a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, a carbon rod is used as the counter electrode, and the substrate is used as the working electrode; the electrolyte is composed of water and ethanol, in which chloroplatinic acid is used as the metal precursor without adding additional ligands;

[0011] (5) The electrodeposition synthesis method uses constant potential amperometry, the potential is set to -0.5 V to -10 V, the deposition time is controlled to 5 min-180 min, and after the electrodeposition reaction is completed, the silicon wafer is taken out, washed with water and ethanol, and dried before characterization.

[0012] Preferably, the steps include:

[0013] (1) First, the substrate is subjected to hydrophilic treatment by a plasma cleaning machine, and then subjected to amino treatment under acidic conditions using a solution of aminopropyltriethoxysilane (APTES);

[0014] (2) The substrate in step (1) is taken out to wash away the excess APTES solution and immersed in a 3-5 nm platinum particle solution;

[0015] (3) The substrate in step (2) is taken out to wash away the excess platinum particle solution, and then an electrolyte is prepared;

[0016] (4) The electrodeposition uses a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, a carbon rod is used as the counter electrode, and the substrate is used as the working electrode; the electrolyte is composed of water and ethanol, in which chloroplatinic acid is used as the metal precursor without adding additional ligands; the pH value of the electrolyte is 1.25-2.79;

[0017] (5) The electrodeposition synthesis method uses constant potential amperometry, the potential is set at -0.5 V to -7 V, the deposition time is controlled at 5 min-180 min, after the electrodeposition reaction is completed, the silicon wafer is taken out, washed with water and ethanol, and dried before characterization.

[0018] Preferably, in step (1), the concentration of the triaminopropyl triethoxysilane is 5 mM.

[0019] Preferably, the substrate is a silicon wafer, a hydrophobic carbon paper, a hydrophilic carbon paper, a hydrophobic carbon cloth, or a conductive glass.

[0020] Preferably, in step (1), the silane coupling agent used for functionalizing the substrate can be triaminopropyl triethoxysilane (APTES) or tricyano propyl triethoxysilane (CPTES).

[0021] Preferably, in step (1), the acid used to treat the substrate is acetic acid.

[0022] Preferably, in step (4), the total volume of the electrolyte is 12 mL, the volume ratio of water to ethanol is 2:1, the concentration of chloroplatinic acid as a metal precursor is 1.2-2.4 mM dissolved in water, and no additional ligand is added during synthesis.

[0023] Preferably, the method comprises the following steps:

[0024] (1) First, the substrate is subjected to 10 min of hydrophilic treatment by a plasma cleaning machine, then subjected to 30 min of amination treatment using a triaminopropyl triethoxysilane solution APTES under acidic conditions, the concentration of the triaminopropyl triethoxysilane is 5 mM, the APTES is dissolved in an equal volume of ethanol and water 1:1, the ethanol is added first and then the water is added when preparing to prevent excessive hydrolysis of the silane coupling agent, and the prepared APTES is mixed with an equal volume of 17.4 M acetic acid to treat the substrate;

[0025] (2) The substrate in step (1) is taken out to wash off the excess APTES solution and soaked in a 3~5 nm platinum particle solution for 2 h;

[0026] (3) The substrate in step (2) is taken out to wash off the excess platinum particle solution, and then the electrolyte is prepared;

[0027] (4) Electrodeposition adopts a three-electrode system, wherein saturated Ag / AgCl is used as a reference electrode, a carbon rod is used as a counter electrode, and a substrate is used as a working electrode; the total volume of an electrolyte is 12 mL, which is mainly composed of water and ethanol, and the volume ratio of water to ethanol is 2:1; wherein chloroplatinic acid 1.2 mM is used as a metal precursor, is dissolved in water, and no ligand is additionally added in the synthesis, but a certain amount of 2 M hydrochloric acid is additionally added, and the pH value of the electrolyte is measured as 1.82;

[0028] (5) The constant potential amperometry is used in the synthesis, the deposition time is 120 min, after the deposition is completed, the substrate is cleaned with ethanol and water, and is dried before characterization, and the black film covering the surface of the substrate indicates that the platinum nanowire array is successfully synthesized.

[0029] In order to solve the technical problems of the present application, another technical solution is provided: the platinum nanowire array can be used in the field of fuel cells or electrochemical catalysis.

[0030] Beneficial effects:

[0031] Compared with the prior art, the present application can synthesize platinum nanowire arrays of different lengths, and the longest length can reach about 10 μm, which is currently not achieved on a planar substrate. This technology breaks through the limitations of templates and ligands, solves the changes in the morphology of nanowires caused by the removal of templates or ligands, and has great application prospects in the fields of catalysis, electronics and optoelectronic devices.

[0032] The platinum nanowires prepared by the present application have unique structural characteristics, and the one-dimensional linear structure can be used in fuel cells such as methanol fuel cells and proton exchange membrane cells, and has good catalytic activity. In addition, the ligand-free synthesis of platinum nanowires reduces the cumbersome step of removing ligands in the catalytic process, and avoids the loss of activity caused by the fact that the active sites in the nanostructure are hindered by ligands and cannot be used, and opens up a new way for the synthesis of nanowires.

[0033] The method has a wide deposition potential range of -0.5 V to -7 V, and by adjusting the deposition time, the length of the platinum nanowire can be controlled on the substrate without templates and small molecule ligands. At the same time, by changing the concentration of the silane coupling agent, the density of the platinum nanowire can be controlled. In addition, the synthesis can also be expanded to conductive substrates, so that the platinum nanowire array can be directly used as a working electrode for subsequent use, providing great application potential for the field of electrocatalysis. The process of the present application is simple, the reaction conditions are mild, the cost is low, and the electrodeposition method for synthesizing nanomaterials has the advantages of precise controllability, simple operation and environmental protection.

[0034] The surface treatment of the substrate in the technology is relatively sensitive, and the number of amino groups on the surface of the substrate has strict requirements. During the amination treatment, acid must be added, such asFigure 1 As shown, the addition of acid promotes the hydrolysis of APTES and inhibits its self-condensation, thereby reducing the number of surface amino groups, so as to obtain a uniform and densely distributed platinum nanowire array.

[0035] In step (2), changing the concentration of the acidified APTES solution can yield platinum nanowires with different densities.

[0036] In step (5), changing the electrochemical deposition time can yield platinum nanowire arrays of different lengths.

[0037] At a chloroplatinic acid concentration of 2.4 mM, we determined the optimal window for electrodepositing platinum nanowires to be -3 V to -7 V. Figure 4 As shown, within this growth window, the synthesized platinum nanowires exhibit excellent uniformity and linear morphology. Beyond the suitable growth window, specifically when the potential reaches -10 V, the reduction rate within the system is too rapid, causing platinum to remain free in the electrolyte due to insufficient time to deposit on the substrate. Furthermore, the electrolyte turns black, resulting in a significant decrease in nanowire density and a substrate dominated by platinum particles. Conversely, at excessively low potentials, the reduction rate is too slow, producing only spherical particles.

[0038] In this invention, we systematically screened the electrolyte pH value that affects the synthesis of platinum nanowires. For example... Figure 4 As shown, when the electrolyte pH drops to 0.85, hydrogen evolution in the reaction becomes more pronounced, competing with the reduced platinum phase. Furthermore, the generation of numerous bubbles hinders nanowire growth, leading to a tendency towards sheet formation. Conversely, as the electrolyte pH increases, the sheet-like structures become smaller, exhibiting a stronger tendency towards linear growth. At pH 1.25, sheet-like growth essentially disappears. When the pH is maintained between 1.25 and 2.79, a uniformly distributed and dense array of platinum nanowires can be obtained on the substrate. However, when the pH rises to neutral or alkaline conditions, only spherical nanoparticles are obtained.

[0039] This invention also relates to growing platinum nanowire arrays on different substrate materials, such as silicon wafers and some highly conductive materials such as carbon paper, carbon cloth, and conductive glass. The universality of this substrate allows conductive materials with platinum nanowire arrays grown on them to be used directly as working electrodes, reducing the inevitable loss of catalysts during catalyst preparation and the problem of loose bonding between the catalyst and the electrode. This has great application potential in electrocatalysis. Attached Figure Description

[0040] Figure 1SEM images of different effects of whether APTES is used for pretreatment of the substrate, APTES concentration and APTES acidification on growth of nanowires in the present application, a is no APTES treatment of the substrate; b-e is APTES treatment of the substrate at different concentrations, specifically (b) 5 mM; (c) 5 x 10 -2 mM; (d) 5 x 10 -3 mM; (e) 5 x 10 -9 mM; f is that the substrate is treated after mixing 5 mM APTES with acetic acid in equal volume ratio.

[0041] Figure 2 SEM images of the substrate treated with APTES acidification solution at different concentrations in the present application, (a) 5 mM; (b) 5 x 10 -1 mM; (c) 5 x 10 -2 mM; (d) 5 x 10 -3 mM.

[0042] Figure 3 SEM images of 2.4 mM chloroplatinic acid at different reduction voltages (a) -1 V; (b) -2 V; (c) -3 V; (d) -7 V; (e) -9 V; (f) -10 V in the present application.

[0043] Figure 4 In the present application, the pH of 2.4 mM chloroplatinic acid is adjusted to (a) 0.85; (b) 1; (c) 1.25; (d) 2.31; (e) 2.79; (f) 3 by adding acid or base.

[0044] Figure 5 SEM images of growth of (a) 5 min; (b) 10 min; (c) 30 min; (d) 60 min; (e) 120 min; (f) 180 min at -5 V reduction potential after adding acid to 1.2 mM chloroplatinic acid in the present application.

[0045] Figure 6 SEM images of growth of platinum nanowire arrays on different substrate surfaces, (a) hydrophobic carbon cloth; (b) hydrophobic carbon paper; (c) conductive glass; (d) hydrophilic carbon paper.

[0046] Figure 7 SEM images of Pt nanowires with lengths of 100 nm, 170 min, 400 nm and 600 nm obtained by controlling the deposition time to be 10 min, 30 min, 60 min and 120 min, respectively, using hydrophilic carbon paper as the substrate.

[0047] Figure 8Area activity plots obtained by cyclic voltammetry (CV) measurements of platinum nanowires grown on hydrophilic carbon paper and traditional commercial platinum carbon as methanol oxidation catalysts. DETAILED DESCRIPTION

[0048] The application will be further described in conjunction with the specific embodiments and drawings

[0049] Example 1

[0050] (1) First, the silicon wafer was treated with a hydrophilic plasma cleaner for 10 min, and then the substrate was treated with an amino solution (APTES) under acidic conditions for 30 min. Specifically, the concentration of the amino solution (APTES) was 5 mM, 5 x 10 -2 mM, 5 x 10 -3 mM, and 5 x 10 -9 mM, respectively.

[0051] The acidified solution of APTES refers to mixing 5 mM of APTES with 17.4 M of acetic acid in an equal volume ratio. During preparation, the APTES was dissolved in an equal volume ratio of 1:1 ethanol and water, and the ethanol was added first and then the water to prevent excessive hydrolysis of the silane coupling agent.

[0052] (2) The substrate in step (1) was taken out and rinsed to remove excess APTES solution, and then immersed in a 3-5 nm platinum particle solution for 2 h.

[0053] (3) The substrate in step (2) was taken out and rinsed to remove excess platinum particle solution, and then an electrolyte was prepared.

[0054] (4) The electrodeposition used a three-electrode system, in which saturated Ag / AgCl was used as the reference electrode, a carbon rod was used as the counter electrode, and the substrate was used as the working electrode. The total volume of the electrolyte was 12 mL, mainly composed of water and ethanol, and the volume ratio of water to ethanol was 2:1. Chloroplatinic acid 2.4 mM was used as the metal precursor, dissolved in water, and the pH value of the electrolyte was measured to be 2.31.

[0055] (5) The constant potential amperometry was used in the synthesis, and the potential was set at -3 V, the deposition time was 10 min, and after the deposition was completed, the substrate was cleaned with ethanol and water, and dried before characterization. The substrate surface was covered with a layer of black film, indicating that the platinum nanowire array was successfully synthesized.

[0056] Figure 1The images show SEM images of substrate pretreatment using APTES, APTES concentration, and the different effects of APTES acidification on nanowire growth. Image a shows a substrate without APTES treatment; images be shows substrates treated with different concentrations of APTES, specifically (b) 5 mM; (c) 5 × 10⁻⁶ mM. -2 mM; (d) 5×10 -3 mM; (e) 5×10 -9 mM;f means mixing 5 mM APTES with acetic acid in an equal volume ratio before treating the substrate.

[0057] The product was analyzed using a scanning electron microscope, such as Figure 1 As shown, the substrate without APTES treatment only yielded a dense layer of platinum nanoparticles. However, as the APTES concentration decreased, linear growth gradually occurred on the substrate surface, and the density increased. Furthermore, the substrate treated with an acidified APTES solution produced a uniform and densely grown array of platinum nanowires. The nanowires (approximately 500 nm in length and 5.5 nm in diameter) grown using an equal volume ratio of 5 mM APTES and acetic acid exhibited the best morphological uniformity.

[0058] Example 2

[0059] (1) First, the silicon wafer was subjected to a 10-minute hydrophilic treatment using a plasma cleaner. Then, the substrate was subjected to an amination treatment for 30 minutes under acidic conditions using a triaminopropyltriethoxysilane solution (APTES). The concentrations of the triaminopropyltriethoxysilane were 5 mM and 5 × 10⁻⁶ mM, respectively. -1 mM, 5×10 -2 mM, 5×10 -3 mM, dissolve APTES in equal volumes of ethanol and water (1:1). Add ethanol first and then water during preparation to prevent excessive hydrolysis of the silane coupling agent. Mix the prepared APTES solution with an equal volume of 17.4 M acetic acid to treat the substrate.

[0060] (2) Take out the substrate from step (1), rinse off the excess APTES solution, and soak it in a solution of 3~5 nm platinum particles for 2 h;

[0061] (3) Take out the substrate from step (2) and rinse off the excess platinum particle solution, and then prepare the electrolyte;

[0062] (4) Electrodeposition was performed using a three-electrode system, in which saturated Ag / AgCl was used as the reference electrode, a carbon rod was used as the counter electrode, and the substrate was used as the working electrode. The total volume of the electrolyte was 12 mL, mainly composed of water and ethanol, with a volume ratio of 2:1. Chloroplatinic acid 2.4 mM was used as the metal precursor and dissolved in water. The pH value of the electrolyte was measured to be 2.31.

[0063] (5) The constant potential amperometry method was used in the synthesis. The potential was set at -3 V and the deposition time was 10 min. After the deposition was completed, the substrate was washed with ethanol and water and dried before characterization. The presence of a black film on the substrate surface indicates that the platinum nanowire array was successfully synthesized.

[0064] Figure 2 The images show SEM images of substrates treated with different concentrations of APTES acidification solution in this invention: (a) 5 mM; (b) 5 × 10⁻⁶ mM. -1 mM; (c) 5×10 -2 mM; (d) 5×10 -3 mM.

[0065] Scanning electron microscopy analysis of the product showed that it was obtained after treating the substrate with an acidified APTES solution. Figure 2 The density of the nanowires shown gradually decreased with decreasing APTES concentration, indicating the formation of more nanoparticles. The nanowires grown using a mixture of 5 mM APTES and acetic acid in an equal volume ratio exhibited the optimal density and morphology.

[0066] Example 3

[0067] (1) First, the silicon wafer was subjected to hydrophilic treatment for 10 min by a plasma cleaner. Then, the substrate was subjected to amination treatment for 30 min by triaminopropyltriethoxysilane solution (APTES) under acidic conditions. Specifically, the concentration of triaminopropyltriethoxysilane was 5 mM (1.10685 mg / mL). APTES was dissolved in an equal volume ratio of ethanol and water (1:1). Ethanol was added first and then water was added during preparation to prevent excessive hydrolysis of the silane coupling agent. The prepared APTES was mixed with an equal volume of acetic acid with a concentration of 17.4 M to treat the substrate.

[0068] (2) Take out the substrate from step (1), rinse off the excess APTES solution, and soak it in a solution of 3~5 nm platinum particles for 2 h;

[0069] (3) Take out the substrate from step (2) and rinse off the excess platinum particle solution, and then prepare the electrolyte;

[0070] (4) Electrodeposition was performed using a three-electrode system, in which saturated Ag / AgCl was used as the reference electrode, a carbon rod was used as the counter electrode, and the substrate was used as the working electrode. The total volume of the electrolyte was 12 mL, mainly composed of water and ethanol, with a volume ratio of 2:1. Chloroplatinic acid 2.4 mM was used as the metal precursor and dissolved in water. The pH value of the electrolyte was measured to be 2.31.

[0071] (5) The constant potential amperometry method was used in the synthesis. The potential was set from -1 V to -10 V and the deposition time was 10 min. After the deposition was completed, the substrate was washed with ethanol and water and dried before characterization. The presence of a black film on the substrate surface indicates that the platinum nanowire array was successfully synthesized.

[0072] Figure 3 The images are SEM images of 2.4 mM chloroplatinic acid obtained under different reduction voltages: (a) -1 V; (b) -2 V; (c) -3 V; (d) -7 V; (e) -9 V; (f) -10 V.

[0073] The product was analyzed using a scanning electron microscope, such as Figure 3 As shown, under the condition of an electrolyte pH of 2.31, the suitable growth window for platinum nanowires was determined to be -3 V to -7 V. When the reduction voltage is -1 V, only a large number of platinum particles can be obtained on the substrate surface. As the reduction voltage shifts negatively (-2 V), nanowires are gradually generated, and when the reduction voltage reaches -3 V, uniformly distributed and densely grown platinum nanowires can be obtained. When the voltage shifts further negatively, up to -10 V, the density and length of the nanowires gradually decrease, at which point the platinum is reduced too quickly and most of it enters the electrolyte.

[0074] Example 4

[0075] (1) First, the silicon wafer was subjected to hydrophilic treatment for 10 min by a plasma cleaner. Then, the substrate was subjected to amination treatment for 30 min by triaminopropyltriethoxysilane solution (APTES) under acidic conditions. Specifically, the concentration of triaminopropyltriethoxysilane was 5 mM (1.10685 mg / mL). APTES was dissolved in an equal volume of ethanol and water at a ratio of 1:1. Ethanol was added first and then water was added during preparation to prevent excessive hydrolysis of the silane coupling agent. The prepared APTES was mixed with an equal volume of 17.4 M acetic acid to treat the substrate.

[0076] (2) Take out the substrate from step (1), rinse off the excess APTES solution, and soak it in a solution of 3~5 nm platinum particles for 2 h;

[0077] (3) Take out the substrate from step (2) and rinse off the excess platinum particle solution, and then prepare the electrolyte;

[0078] (4) Electrodeposition adopts a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, carbon rod is used as the counter electrode, and substrate is used as the working electrode; the total volume of the electrolyte is 12 mL, mainly composed of water and ethanol, with a volume ratio of water to ethanol of 2:1; chloroplatinic acid 2.4 mM is used as the metal precursor, dissolved in water, and the pH value of the electrolyte is measured to be 2.31. Hydrochloric acid or sodium hydroxide is added to the electrolyte to adjust the pH value.

[0079] (5) The constant potential amperometry method was used in the synthesis. The potential was set at -3 V and the deposition time was 10 min. After the deposition was completed, the substrate was washed with ethanol and water and dried before characterization. The presence of a black film on the substrate surface indicates that the platinum nanowire array was successfully synthesized.

[0080] Figure 4 In this invention, the pH of 2.4 mM chloroplatinic acid was adjusted to (a) 0.85; (b) 1; (c) 1.25; (d) 2.31; (e) 2.79; (f) 3 by adding acid or base.

[0081] The product was analyzed using a scanning electron microscope. Figure 4 As shown, when the electrolyte pH drops to 0.85, hydrogen evolution in the reaction becomes more pronounced, competing with the reduced platinum phase. Furthermore, the generation of numerous bubbles hinders nanowire growth, leading to a tendency towards sheet formation. Conversely, as the electrolyte pH increases, the sheet-like structures become smaller, exhibiting a stronger tendency towards linear growth. At pH 1.25, sheet-like growth essentially disappears. When the pH is maintained between 1.25 and 2.79, a uniformly distributed and dense array of platinum nanowires can be obtained on the substrate. However, when the pH rises to neutral or alkaline conditions, only spherical nanoparticles are obtained.

[0082] Example 5

[0083] (1) First, the silicon wafer was subjected to hydrophilic treatment for 10 min by a plasma cleaner. Then, the substrate was subjected to amination treatment for 30 min by triaminopropyltriethoxysilane solution (APTES) under acidic conditions. Specifically, the concentration of triaminopropyltriethoxysilane was 5 mM (1.10685 mg / mL). APTES was dissolved in an equal volume ratio of ethanol and water (1:1). Ethanol was added first and then water was added during preparation to prevent excessive hydrolysis of the silane coupling agent. The prepared APTES was mixed with an equal volume of 17.4 M acetic acid to treat the substrate.

[0084] (2) Take out the substrate from step (1), rinse off the excess APTES solution, and soak it in a solution of 3~5 nm platinum particles for 2 h;

[0085] (3) Take out the substrate from step (2) and rinse off the excess platinum particle solution, and then prepare the electrolyte;

[0086] (4) Electrodeposition adopts a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, carbon rod is used as the counter electrode, and substrate is used as the working electrode; the total volume of the electrolyte is 12 mL, mainly composed of water and ethanol, with a volume ratio of water to ethanol of 2:1; 1.2 mM chloroplatinic acid is used as the metal precursor, dissolved in water, and no additional ligand is added in the synthesis, but a certain amount of 2 M hydrochloric acid is added, and the pH value of the electrolyte is measured to be 1.82;

[0087] (5) The constant potential amperometry method was used in the synthesis. The potential was set at -5 V, and the deposition times were 5 min, 10 min, 30 min, 60 min, 120 min and 180 min, respectively. After deposition, the substrate was washed with ethanol and water and dried before characterization. The presence of a black film on the substrate surface indicates that the platinum nanowire array was successfully synthesized.

[0088] Figure 5 The images show SEM images of the growth process in this invention, where acid was added to 1.2 mM chloroplatinic acid and the growth was carried out at a reduction potential of -5 V for (a) 5 min; (b) 10 min; (c) 30 min; (d) 60 min; (e) 120 min; and (f) 180 min.

[0089] Scanning electron microscopy analysis of the product showed that adding acid to 1.2 mM chloroplatinic acid in the electrolyte condition increased the length of the nanowires to nearly 10 μm, while the length of the nanowires grown under the original electrolyte condition (2.4 mM chloroplatinic acid) could only reach about 1 μm. Figure 5 As shown, the length of the nanowires increases linearly with deposition time, with lengths of 250 nm, 500 nm, 1 μm, 1.5 μm, 3 μm, and 9.5 μm, and a diameter of 5.5 nm.

[0090] Example 6

[0091] (1) First, the conductive substrate, such as carbon paper, carbon cloth, and conductive glass, is subjected to hydrophilic treatment for 15 min by a plasma cleaner. Then, the substrate is subjected to amination treatment for 10 min by triaminopropyltriethoxysilane solution (APTES) under acidic conditions. Specifically, the concentration of triaminopropyltriethoxysilane is 5 mM (1.10685 mg / mL). APTES is dissolved in an equal volume ratio of ethanol and water (1:1). Ethanol is added first and then water is added during preparation to prevent excessive hydrolysis of the silane coupling agent. The prepared APTES is mixed with an equal volume of 17.4 M acetic acid to treat the substrate.

[0092] (2) Take out the substrate from step (1), rinse off the excess APTES solution, and soak it in a solution of 3~5 nm platinum particles for 2 h;

[0093] (3) Take out the substrate from step (2) and rinse off the excess platinum particle solution, and then prepare the electrolyte;

[0094] (4) Electrodeposition was performed using a three-electrode system, in which saturated Ag / AgCl was used as the reference electrode, a carbon rod was used as the counter electrode, and the substrate was used as the working electrode. The total volume of the electrolyte was 12 mL, mainly composed of water and ethanol, with a volume ratio of 2:1. Chloroplatinic acid 1.2 mM was used as the metal precursor and dissolved in water. In addition, 2 M hydrochloric acid was added to the electrolyte, and the pH value of the electrolyte was measured to be 1.82.

[0095] (5) The constant potential amperometry method was used in the synthesis. The potential was set at -0.5 V and the deposition time was 10 min. After the deposition was completed, the mixture was washed with ethanol and water and dried before characterization.

[0096] Figure 6 SEM images of platinum nanowire arrays grown on different substrate surfaces: (a) hydrophobic carbon cloth; (b) hydrophobic carbon paper; (c) conductive glass; (d) hydrophilic carbon paper.

[0097] The product was analyzed using a scanning electron microscope, such as Figure 6 As shown, based on the above-mentioned control experiments using silicon wafers as the substrate, the optimal synthesis conditions for platinum nanowires were obtained. These conditions were directly applied to conductive substrates. Since the internal resistance of silicon wafers is much higher than that of conductive substrates, an optimal growth potential of -0.5 V for platinum nanowires on conductive substrates was found. The nanowires grown on hydrophobic carbon cloth / carbon paper were a mixture of nanowires and nanoparticles. The nanowire density grown on conductive glass was very low, while the nanowires grown on hydrophilic carbon paper showed the best uniformity and morphology. Furthermore, as... Figure 7 As shown, by adjusting the deposition time, platinum nanowires of different lengths can be obtained on hydrophilic carbon paper. Deposition times of 10 min, 30 min, 60 min, and 120 min yield nanowires with lengths of 100 nm, 170 nm, 400 nm, and 600 nm, respectively. Furthermore, the platinum nanowires obtained on the conductive substrate can be directly used in catalytic reactions, reducing problems in traditional catalyst preparation processes such as catalyst loss or weak bonding between the catalyst and the electrode, thus greatly promoting the development of electrocatalysis.

[0098] Electrochemical tests were then performed using a three-electrode system: a graphite rod as the counter electrode; a saturated calomel electrode (SCE) as the reference electrode; and a hydrophilic carbon paper on which platinum nanowires were grown as the working electrode. The electrolyte was a 1 M KOH and 0.5 M methanol aqueous solution. Cyclic voltammetry (CV) was performed at a scan rate of 50 mV / s.

[0099] Figure 8 Area activity maps measured by cyclic voltammetry (CV) when platinum nanowires of different lengths are grown on hydrophilic carbon paper and when conventional commercial platinum carbon is used as a methanol oxidation catalyst.

[0100] like Figure 8 As shown, electrochemical tests indicate that the longer the platinum nanowire, the greater its area activity, with the 600 nm long platinum nanowire achieving an area activity of 217 mA / cm². -2 The surface activity of commercial Pt / C is only 17.4 mA / cm². -2 Therefore, the current density of ligand-free platinum nanowires exhibits 10 times the catalytic efficiency of methanol oxidation compared to traditional commercial platinum carbon, and its positive oxidation peak potential is delayed, indicating that it enhances the inhibition of carbon-containing oxides.

[0101] This invention is not limited to the specific technical solutions described in the above embodiments. Any modification or equivalent substitution of this invention to achieve the same technical effect is within the scope of protection of this invention.

Claims

1. A ligand-free electrodeposition method for synthesizing arrays of platinum nanowires on a substrate, characterized in that :Comprising the following steps: (1) First, the substrate is treated with hydrophilic by plasma cleaner, then the substrate is treated with amino by using APTES solution in acid condition; (2) The substrate in step (1) is taken out to wash away the excess APTES solution, and then immersed in 3-5 nm platinum particle solution; (3) The substrate in step (2) is taken out to wash away the excess platinum particle solution, and then the electrolyte is prepared; (4) The electrodeposition uses a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, a carbon rod is used as the counter electrode, and the substrate is used as the working electrode; the electrolyte is composed of water, ethanol, chloroplatinic acid and hydrochloric acid, in which chloroplatinic acid is used as the metal precursor, and the pH value of the electrolyte is 1.25-2.79; (5) The electrodeposition synthesis method uses constant potential amperometry, the potential is set to-0.5 V to-7 V, the deposition time is controlled to 5 min-180 min, after the electrodeposition reaction is completed, the silicon wafer is taken out, washed with water and ethanol, and dried before characterization.

2. The ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate according to claim 1, characterized in that: In step (1), the concentration of the triaminopropyl triethoxysilane is 5 mM.

3. The ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate according to claim 1, characterized in that: The substrate is a silicon wafer, a hydrophobic carbon paper, a hydrophilic carbon paper, a hydrophobic carbon cloth or a conductive glass.

4. The ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate according to claim 1, characterized in that In step (1), the acid used to treat the substrate is acetic acid.

5. The ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate according to claim 1, characterized in that In step (4), the total volume of the electrolyte is 12 mL, the volume ratio of water to ethanol is 2:1, and the concentration of chloroplatinic acid as the metal precursor dissolved in water is 1.2-2.4 mM.

6. The ligand-free electrodeposition method for synthesizing platinum nanowire arrays on a substrate according to claim 1, characterized in that The substrate is a hydrophilic carbon paper.

7. The ligand-free electrodeposition method for synthesizing arrays of platinum nanowires on a substrate according to claim 1, wherein :Comprising the following steps: (1) First, the substrate is treated with hydrophilic for 10 min by plasma cleaner, then the substrate is treated with amino for 30 min by using APTES solution in acid condition, the concentration of the triaminopropyl triethoxysilane is 5 mM, the APTES is dissolved in equal volume of ethanol and water 1:1, add ethanol first and then add water when preparing to prevent excessive hydrolysis of silane coupling agent, after the preparation of APTES is completed, mix with equal volume of 17.4 M acetic acid to treat the substrate; (2) The substrate in step (1) is taken out to wash away the excess APTES solution, and then immersed in 3-5 nm platinum particle solution for 2 h; (3) The substrate in step (2) is taken out to wash away the excess platinum particle solution, and then the electrolyte is prepared; (4) The electrodeposition uses a three-electrode system, in which saturated Ag / AgCl is used as the reference electrode, a carbon rod is used as the counter electrode, and the substrate is used as the working electrode; the total volume of the electrolyte is 12 mL, the volume ratio of water to ethanol is 2:1; the concentration of chloroplatinic acid is 1.2 mM, and the concentration of hydrochloric acid is 2 M, and the pH value of the electrolyte is 1.82; (5) The synthesis uses constant potential amperometry, the deposition time is 120 min, after the deposition is completed, the substrate is washed with ethanol and water, and dried before characterization, and a layer of black film is covered on the surface of the substrate, indicating that the platinum nanowire array is successfully synthesized.

8. Use of a platinum nanowire array prepared according to any one of claims 1 to 7, characterized in that The platinum nanowire array can be used as a methanol oxidation catalyst.

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