A gold nanowire catalyst, a preparation method and application thereof

Abstract

This invention discloses a gold nanowire catalyst, its preparation method, and its applications, belonging to the field of nanomaterials technology. The method involves adding a gold perchlorate solution to a hexadecyltrimethylammonium bromide solution, mixing them at a specific volume ratio, and then adding a freshly prepared ascorbic acid solution to the mixture. The mixture is then shaken to obtain extremely fine, elongated gold nanowires with an aspect ratio of (100-200):1. This invention provides a novel preparation method for addressing the morphology issues in the synthesis of gold nanowires, and the prepared gold nanowires can be applied in the field of electrocatalytic CO2 reduction, significantly improving the selectivity for CO2 reduction to CO.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, and more specifically to a gold nanowire catalyst, its preparation method, and its application. Background Technology

[0002] Current societal development relies heavily on the combustion of non-renewable energy sources such as coal, oil, and natural gas, resulting in the annual generation of large amounts of CO2 and causing a series of problems, including resource shortages. Electrocatalytic CO2 reduction has become a hot topic in the field of CO2 catalysis due to its advantages such as easy reaction control and mild reaction conditions, which can realize the conversion and utilization of carbon resources and alleviate the aforementioned resource shortages and global warming caused by excessive CO2 production.

[0003] As is well known in the art, the electrocatalytic reduction of CO2 is a slow kinetic process with numerous side reactions and complex operation, typically involving two, four, six, or eight electron transfers, yielding a variety of products, such as high-value carbon-based products like CO, HCOOH, and CH3OH. Therefore, this reaction often suffers from low selectivity and poor stability. Since CO is a gas at atmospheric pressure, it is easily separated from the electrolyte, and CO has important applications in the metallurgical and chemical industries. Therefore, research on the electrocatalytic reduction of CO2 to CO has significant application value. The process of electrocatalytic reduction of CO2 to CO involves electrochemistry and thermochemistry, and the specific reaction mechanism is as follows:

[0004] CO+(H + +e - →COOH ads (1)

[0005] COOH ads +(H + +e - )→CO ads +H2O (2)

[0006] CO ads +H2O→CO(g)+H2O (3)

[0007] Therefore, gold nanomaterials have emerged in the field of electrocatalytic CO2 reduction to CO to improve the selectivity of CO2 reduction to CO. Gold nanomaterials exhibit high selectivity in the electrocatalytic reduction of CO2 to CO. However, different morphologies of gold nanoparticles, such as nanowires, nanoparticles, nanocubes, and nanosheets, have varying effects on the selective reduction of CO2 to CO. Furthermore, the morphology of existing gold nanomaterials is difficult to control, often resulting in aggregation during synthesis and difficulty in controlling crystal orientation, thus preventing the formation of gold nanowires.

[0008] Therefore, developing a simple and morphology-controllable gold nanowire synthesis method and its preparation method for electrocatalytic reduction of CO2 to CO is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] In view of this, the present invention provides a novel method for preparing gold nanowires. This method can prepare gold nanowires with controllable morphology, which not only avoids the problems of agglomeration and difficulty in controlling crystal orientation during the preparation process, but also improves the selectivity of electrocatalytic reduction of CO2 to CO, realizing the application of gold nanowires in the field of electrocatalytic reduction of CO2 to CO.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing a gold nanowire solution includes: pouring a 0.4-0.8 mmol / L gold perchlorate solution into a 5-15 mmol / L hexadecyltrimethylammonium bromide solution and mixing them; then slowly adding a freshly prepared ascorbic acid solution to the mixed solution; and finally shaking and allowing it to stand to obtain the gold nanowire solution.

[0012] The beneficial effects achieved by the above technical solution are as follows: ascorbic acid solution acts as a reducing agent to reduce perchloroauric acid to elemental gold; hexadecyltrimethylammonium bromide solution acts as a surface passivating agent to prevent gold agglomeration due to high surface energy during nucleation; and simultaneously acts as an inducing agent to induce the formation of gold nanowires. Compared with other existing technologies, the preparation method defined in this invention is very simple and can easily prepare gold nanowires without the need for hydrothermal or other complex synthesis processes.

[0013] Preferably, before mixing, the volume ratio of the gold perchlorate solution to the hexadecyltrimethylammonium bromide solution is 1:(0.5-2).

[0014] Preferably, the concentration of ascorbic acid is 0.05-0.15 mol / L.

[0015] Preferably, the volume ratio of ascorbic acid to the mixed solution is 1:(75-125).

[0016] Preferably, the settling time is 20-40 minutes.

[0017] The beneficial effects achieved by the above preparation conditions are as follows: Long, narrow gold nanowires can be prepared under the conditions defined in this invention. If the conditions are not within the defined range, the synthesis of gold nanowires will fail, resulting in other morphologies such as particles or polygons, leading to a non-uniform or destroyed nanowire morphology. This, in turn, affects the selectivity of the electrocatalytic reduction of CO2 to CO.

[0018] A gold nanowire solution prepared by the above preparation method.

[0019] The beneficial technical effects achieved by the above technical solution are as follows: the gold nanowires synthesized by this method can be used for electrocatalytic reduction of CO2 to produce CO, and exhibit extremely high selectivity for CO. CO2 is adsorbed on the surface of the gold nanowires to form a COOH* intermediate, and then the OH group is removed to form CO* before being directly desorbed on the surface of the gold nanowires to form CO. Therefore, the selectivity for reducing CO2 to CO can be greatly improved.

[0020] Preferably, the gold nanowires in the gold nanowire solution are elongated strips with an aspect ratio of (100-200):1.

[0021] A method for electrocatalytic reduction of CO2 involves dropping a gold nanowire solution prepared by the above method onto carbon paper as a cathode electrode catalyst, and then performing electrocatalytic reduction of CO2 to CO in an electrolyte.

[0022] Preferably, the electrolyte is KHCO3.

[0023] An electrolytic cell for the electrocatalytic reduction of CO2 includes a cathode electrode on which a gold nanowire solution prepared by the above-described preparation method is loaded.

[0024] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a gold nanowire catalyst, its preparation method and application, which has the following beneficial effects:

[0025] 1. This invention provides a simple and easy-to-implement method for preparing gold nanowires with controllable morphology;

[0026] 2. The gold nanowire solution synthesized in this invention can be used for electrocatalytic reduction of CO2 to produce CO, and has extremely high selectivity for CO. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 Scanning electron microscope image of the gold nanowires prepared in Example 1;

[0029] Figure 2 for Figure 1 A further enlarged view;

[0030] Figure 3 The image shows the Faraday efficiency of the gold nanowire electrocatalytic CO2 reduction prepared in Example 1. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention discloses a method for preparing a gold nanowire solution, specifically including the following steps:

[0033] A gold nanowire solution was prepared by adding a 0.4-0.8 mmol / L gold perchlorate solution to a 5-15 mmol / L hexadecyltrimethylammonium bromide solution at a volume ratio of 1:(0.5-2). After thorough mixing, freshly prepared ascorbic acid solution was slowly added dropwise to the mixture at a volume ratio of 1:(75-125). The mixture was shaken and allowed to stand for 20-40 minutes. The gold nanowires in this solution were elongated strips with an aspect ratio of (100-200):1.

[0034] Example 1

[0035] A method for preparing a gold nanowire solution, specifically including the following steps:

[0036] Add 5 mL of 10 mmol / L hexadecyltrimethylammonium bromide solution to 5 mL of 0.6 mmol / L gold perchlorate solution, mix them thoroughly, then add 0.1 mL of freshly prepared 0.1 mol / L ascorbic acid solution to the mixture, shake gently, and let stand for half an hour to obtain the gold nanowire solution.

[0037] like Figure 1 and Figure 2 As shown, the gold nanowires in solution prepared by Example 1 have the morphological characteristics of being slender nanowires with an aspect ratio of (100-200):1.

[0038] Example 2

[0039] The gold nanowire solution prepared in Example 1 was used for the electrocatalytic reduction of CO2 to CO. Specifically, the electrocatalysis was performed as follows: the gold nanowire solution was washed with deionized water to remove surfactants, then dissolved in deionized water, and an appropriate amount of carbon powder was added to prepare a suspension of 10 mg carbon powder / mL. This suspension was then dropped onto the cathode carbon paper as the carbon dioxide reduction electrode. A 0.1 M KHCO3 solution was added to an H-type electrolytic cell, ensuring it covered the electrode. Carbon dioxide was then continuously introduced into the cathode chamber, and an electrocatalytic carbon dioxide reduction degradation experiment was conducted using an electrochemical workstation. The IT measurement method was used to conduct electrolysis experiments at different potentials (-0.9 V to -1.3 V vs. RHE) to obtain the carbon dioxide reduction efficiency at different potentials. For details, please refer to [link to details]. Figure 3 .

[0040] Conclusion: In 0.1M KHCO3 solution, the gold nanowires exhibit a selectivity for CO of up to 90% or more (≤-1.2V vs RHE), thus demonstrating extremely high catalytic activity for CO2 reduction.

[0041] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0042] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a gold nanowire solution, characterized in that, Pour a 0.4-0.8 mmol / L gold perchlorate solution into a 5-15 mmol / L hexadecyltrimethylammonium bromide solution, mix well, and then slowly add a freshly prepared ascorbic acid solution to the mixture. After shaking and standing, a gold nanowire solution is obtained. Before mixing, the volume ratio of the gold perchlorate solution to the hexadecyltrimethylammonium bromide solution was 1:(0.5-2); The concentration of the ascorbic acid solution is 0.05-0.15 mol / L; The volume ratio of the ascorbic acid solution to the mixed solution is 1:(75-125).

2. The method for preparing a gold nanowire solution according to claim 1, characterized in that, The settling time is 20-40 minutes.

3. The method for preparing a gold nanowire solution according to claim 1, characterized in that, The gold nanowires in the gold nanowire solution are elongated strips with an aspect ratio of (100-200):1.

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