技术领域technical field
本发明属于复合催化剂制备领域，特别涉及一种贵金属/竖直生长水滑石纳米片甲醇燃料电池催化剂的制备方法。The invention belongs to the field of composite catalyst preparation, in particular to a preparation method of a noble metal/vertical growth hydrotalcite nanosheet methanol fuel cell catalyst.
背景技术Background technique
在生产力和人类生活水平日益进步的今天，对能源的需求和依赖急剧增长，使得传统化石燃料的消耗与日俱增，随之而来的是对生存环境的破坏。因此，急需寻找一种可再生的替代能源，减少化石燃料的燃烧，缓解环境的压力。甲醇燃料电池作为一种便携式新型能源，由于其可以将化学能直接转化为电能，因此不受卡诺循环的限制，能量转化率可达到80％以上，具有能量密度高的优点，同时不需要传统繁琐的充放电过程，操作简单、使用方便，近年来已引起了广泛关注。但甲醇燃料电池用于催化阳极氧化反应的贵金属催化剂，在催化过程中中间产物CO极容易吸附于贵金属表面，占据了甲醇催化氧化的活性位点，从而极大降低了贵金属催化活性。同时在催化过程中随着反应的不断进行，贵金属催化剂会随着反应的进行发生聚集，进一步降低了贵金属的催化活性。Today, with the improvement of productivity and human living standards, the demand and dependence on energy are increasing rapidly, which makes the consumption of traditional fossil fuels increase day by day, followed by the destruction of the living environment. Therefore, it is urgent to find a renewable alternative energy source to reduce the burning of fossil fuels and relieve the pressure on the environment. As a portable new energy source, methanol fuel cell is not limited by the Carnot cycle because it can directly convert chemical energy into electrical energy, and the energy conversion rate can reach more than 80%, which has the advantage of high energy density and does not require traditional The cumbersome charging and discharging process, simple operation and convenient use have attracted widespread attention in recent years. However, the noble metal catalysts used in methanol fuel cells to catalyze the anodic oxidation reaction, the intermediate product CO is easily adsorbed on the surface of noble metals during the catalytic process, occupying the active sites of methanol catalytic oxidation, thus greatly reducing the catalytic activity of noble metals. At the same time, with the continuous progress of the reaction in the catalytic process, the noble metal catalyst will aggregate with the progress of the reaction, further reducing the catalytic activity of the noble metal.
水滑石又称为层状双金属氢氧化物，是一种典型的阴离子型插层材料，其化学结构式可以表示为[M2+1-x M3+x(OH)2](An-)x/n﹒mH2O，其中M2+和M3+分别代表二价和三价的金属阳离子，An-为层间阴离子。水滑石作为一种超分子复合材料，由于其具有特殊的拓扑结构，较大的比表面积，和优良的电化学性质，近年来在超级电容器、电催化等领域已引起了广泛关注。Hydrotalcite, also known as layered double metal hydroxide, is a typical anionic intercalation material, and its chemical structure can be expressed as [M2+1-x M3+x (OH)2](An- )x/n . mH2 O, where M2+ and M3+ represent divalent and trivalent metal cations, respectively, andAn- is an interlayer anion. As a supramolecular composite material, hydrotalcite has attracted extensive attention in the fields of supercapacitors and electrocatalysis in recent years due to its special topological structure, large specific surface area, and excellent electrochemical properties.
关于现有技术中利用水滑石作为前体制备甲醇燃料电池催化剂中，李峰、张春芳等人研究了一种燃料电池用电催化剂，利用水滑石作为前体，一步法合成金属单质/多壁碳纳米管型复合材料；然后将该复合材料与石墨、聚四氟乙烯混合成膏状，均匀的涂负在碳纸的表面，使涂覆的面积为0.5～1.0cm2；再利用电化学沉积法，在其表面负载上贵金属Pt粒子，制成燃料电池用电催化剂。其中，前体水滑石的作用是形成碳纳米管，而且该催化剂的制备方法相对复杂，制备温度高，需要精确控制的工艺条件较多，不适合大规模生产，同时利用电沉积负载的贵金属Pt粒子尺寸较大，分布不均匀。随着甲醇氧化反应的进行，贵金属表面易被CO等中间产物占据活性位点，稳定性能较差。Regarding the use of hydrotalcite as a precursor in the preparation of catalysts for methanol fuel cells in the prior art, Li Feng, Zhang Chunfang and others studied an electrocatalyst for fuel cells, using hydrotalcite as a precursor to synthesize metal element/multi-walled carbon nanometers in one step Tubular composite material; then mix the composite material with graphite and polytetrafluoroethylene to form a paste, and apply it evenly on the surface of carbon paper, so that the coated area is 0.5-1.0cm2 ; and then use the electrochemical deposition method , loaded on the surface of noble metal Pt particles, made of electrocatalysts for fuel cells. Among them, the function of the precursor hydrotalcite is to form carbon nanotubes, and the preparation method of the catalyst is relatively complicated, the preparation temperature is high, and there are many process conditions that need to be precisely controlled, which is not suitable for large-scale production. The particle size is large and the distribution is uneven. As the methanol oxidation reaction proceeds, the surface of noble metals is easily occupied by intermediate products such as CO, leading to poor stability.
综上所述，现有技术中对于甲醇燃料电池催化剂存在中间产物CO容易吸附贵金属表面、贵金属催化剂容易发生聚集、以及催化剂制备方法复杂等问题，尚缺乏有效的解决方案。To sum up, in the prior art, there is still no effective solution to the problems that the intermediate product CO is easily adsorbed on the surface of noble metals, the aggregation of noble metal catalysts is easy to occur, and the catalyst preparation method is complicated, etc. in methanol fuel cell catalysts.
发明内容Contents of the invention
为了克服现有技术中甲醇燃料电池催化剂的制备方法的缺点，本发明的第一个目的是提供了一种贵金属/竖直生长水滑石纳米片的制备方法，该制备方法简单容易操作，优于现有技术中甲醇燃料电池催化剂的操作步骤，同时贵金属盐溶液可以重复使用极大降低了使用成本。In order to overcome the shortcoming of the preparation method of methanol fuel cell catalyst in the prior art, the first object of the present invention is to provide a kind of preparation method of noble metal/vertical growth hydrotalcite nanosheet, and this preparation method is simple and easy to operate, and is superior to The operation steps of the methanol fuel cell catalyst in the prior art, meanwhile, the precious metal salt solution can be reused, which greatly reduces the use cost.
为实现上述目的，本发明具体采用以下技术方案：To achieve the above object, the present invention specifically adopts the following technical solutions:
一种贵金属/竖直生长水滑石纳米片的制备方法，包括以下步骤：A preparation method of noble metal/vertically growing hydrotalcite nanosheets, comprising the following steps:
(1)将水滑石(LDH)生长所需模板清洗后进行刻蚀，刻蚀后清洗干净；(1) After cleaning the template required for hydrotalcite (LDH) growth, etch it, and clean it after etching;
(2)以甲醇和水的混合溶液作为溶剂，溶解水滑石生长所需要的两种或三种前驱体金属盐和十六烷基三甲基溴化铵(CTAB)，形成均一溶液；(2) Using a mixed solution of methanol and water as a solvent to dissolve two or three precursor metal salts and cetyltrimethylammonium bromide (CTAB) required for hydrotalcite growth to form a homogeneous solution;
(3)将步骤(1)中清洗干净后的模板放入步骤(2)中的均一溶液中，进行水热反应；反应完毕，清洗模板表面并干燥，即得到在模板表面上竖直生长的水滑石纳米片；(3) Put the template cleaned in step (1) into the homogeneous solution in step (2), and carry out hydrothermal reaction; after the reaction is completed, clean the template surface and dry it to obtain the vertical growth on the template surface Hydrotalcite nanosheets;
(4)将步骤(3)中的在模板表面上竖直生长的水滑石纳米片放置在贵金属盐溶液中，进行氧化还原反应，反应完毕后清洗、干燥即得到贵金属/竖直生长水滑石纳米片。(4) Place the hydrotalcite nanosheets grown vertically on the surface of the template in step (3) in a noble metal salt solution to carry out a redox reaction. After the reaction is completed, wash and dry to obtain noble metal/vertically grown hydrotalcite nanosheets. piece.
步骤(1)和(2)的顺序可互调。The order of steps (1) and (2) is interchangeable.
步骤(1)中，水滑石(LDH)生长所需模板为导电基底，例如：泡沫镍、碳纤维布、碳纸等。In step (1), the template required for the growth of hydrotalcite (LDH) is a conductive substrate, for example: nickel foam, carbon fiber cloth, carbon paper, etc.
采用此生长模板的作用是：为水滑石的生长提供附着基质，使水滑石能够竖直生长。The function of using the growth template is to provide an attachment substrate for the growth of the hydrotalcite, so that the hydrotalcite can grow vertically.
本发明采用盐酸溶液对模板进行刻蚀，刻蚀所产生的效果是：导电基底表面产生缺陷，利于随后水滑石纳米片的附着，以及竖直形貌的形成。The present invention uses hydrochloric acid solution to etch the template, and the effect of the etching is: defects are generated on the surface of the conductive substrate, which is beneficial to the subsequent attachment of hydrotalcite nanosheets and the formation of vertical morphology.
步骤(1)的具体方法，包括：将水滑石生长所需模板用丙酮彻底清洗，并用盐酸溶液进行刻蚀，刻蚀后用无水乙醇以及二次水清洗，至彻底清洗干净。The specific method of step (1) includes: thoroughly cleaning the template required for hydrotalcite growth with acetone, etching with hydrochloric acid solution, and cleaning with absolute ethanol and secondary water after etching until thoroughly cleaned.
优选的，第一次清洗处理时，丙酮的使用量为200～500mL，分多次清洗，针对模板大小的是(0.4～1)cm×(2～4)cm。Preferably, in the first cleaning treatment, the amount of acetone used is 200-500 mL, and the cleaning is divided into multiple times, and the size of the template is (0.4-1) cm×(2-4) cm.
为达到更好的刻蚀效果，所述盐酸溶液的浓度为0.5～5mol·L-1，使用量在能够全部覆盖模板为宜；刻蚀时间为10～20min。In order to achieve a better etching effect, the concentration of the hydrochloric acid solution is 0.5-5 mol·L-1 , and the usage amount is suitable for covering all the templates; the etching time is 10-20 minutes.
第二次清洗处理时，无水乙醇以及二次水应交替清洗6～8次，才可以将模板彻底清洗干净。During the second cleaning process, anhydrous ethanol and secondary water should be washed alternately for 6-8 times before the template can be thoroughly cleaned.
步骤(2)中，本领域技术人员知晓合成水滑石的前驱体金属盐的种类，对此并不需要特别限定。In step (2), those skilled in the art know the types of precursor metal salts for synthesizing hydrotalcite, and there is no need for special limitations.
优选的，以最终形成的贵金属/竖直生长水滑石纳米片的催化效果来讲，所述前驱体金属盐为镍盐、钴盐、铁盐、铝盐、铜盐、镁盐、锌盐或其他金属盐。Preferably, in terms of the catalytic effect of the finally formed noble metal/vertically grown hydrotalcite nanosheets, the precursor metal salt is nickel salt, cobalt salt, iron salt, aluminum salt, copper salt, magnesium salt, zinc salt or other metal salts.
优选的，以最终形成的贵金属/竖直生长水滑石纳米片的催化效果来讲，LDH两种或三种前驱体金属盐摩尔比例，两种为1:3～1:8，三种为1:3:5～1:8:10，经过研究发现，此比例形成的水滑石纳米片分散均匀，尺寸较均一，有效增加了其表面积，有利于贵金属纳米颗粒的负载。Preferably, in terms of the catalytic effect of the final noble metal/vertically grown hydrotalcite nanosheets, the molar ratio of two or three precursor metal salts of LDH is 1:3 to 1:8 for two types, and 1:3 for three types. :3:5～1:8:10. After research, it is found that the hydrotalcite nanosheets formed by this ratio are uniformly dispersed and relatively uniform in size, which effectively increases its surface area and is conducive to the loading of noble metal nanoparticles.
本发明以十六烷基三甲基溴化铵为导向剂。十六烷基三甲基溴化铵作为一种阳离子表面活性剂，在水滑石形成的过程中，以甲醇和水为溶剂，能够控制水滑石形貌，容易得到分布均匀和尺寸较均一的水滑石纳米片。优选的，总金属离子与CTAB的摩尔比为(5～100)：1。The present invention uses cetyltrimethylammonium bromide as the guiding agent. Cetyltrimethylammonium bromide is a cationic surfactant. In the process of hydrotalcite formation, methanol and water are used as solvents to control the morphology of hydrotalcite, and it is easy to obtain water with uniform distribution and relatively uniform size. Talc nanosheets. Preferably, the molar ratio of total metal ions to CTAB is (5-100):1.
采用不同的溶剂能够合成不同形貌的水滑石材料，本发明选择甲醇和水的混合溶液为溶剂，能够得到性质稳定的水滑石纳米片。优选的，所述甲醇和水的体积比例为：5:1～3:1。Different solvents can be used to synthesize hydrotalcite materials with different shapes. In the present invention, a mixed solution of methanol and water is selected as a solvent to obtain hydrotalcite nanosheets with stable properties. Preferably, the volume ratio of methanol to water is 5:1˜3:1.
步骤(3)中，水热反应的温度和时间对水滑石产物的形貌具有一定影响，从得到水滑石产物的良好片状形态来讲，优选的，所述水热反应的温度为120～200℃，反应时间为12～24h。In step (3), the temperature and time of the hydrothermal reaction have a certain influence on the morphology of the hydrotalcite product. From the perspective of obtaining a good sheet shape of the hydrotalcite product, preferably, the temperature of the hydrothermal reaction is 120- 200°C, the reaction time is 12 to 24 hours.
该步骤中得到的LDH所具有的竖直生长的特殊形貌，极大的增加了其作为载体的比表面积，更有利于负载贵金属催化剂材料。The special morphology of the vertical growth of the LDH obtained in this step greatly increases its specific surface area as a carrier, which is more conducive to supporting noble metal catalyst materials.
步骤(4)中，为了更有利于贵金属的氧化还原反应，优选的，贵金属盐溶液的pH为7～11。In step (4), in order to be more conducive to the redox reaction of the noble metal, preferably, the pH of the noble metal salt solution is 7-11.
优选的，所述贵金属盐为Pt盐、Ru盐、Au盐或其他贵金属盐中的一种或多种，具体可为Na2PtCl6，RuCl3·3H2O，HAuCl4·4H2O等。从提高贵金属/竖直生长水滑石纳米片的催化效果来讲，优选的，所述贵金属盐溶液的浓度为0.01～0.1mol﹒L-1。Preferably, the noble metal salt is one or more of Pt salt, Ru salt, Au salt or other noble metal salts, specifically Na2 PtCl6 , RuCl3 ·3H2 O, HAuCl4 ·4H2 O, etc. . In terms of improving the catalytic effect of noble metal/vertically grown hydrotalcite nanosheets, preferably, the concentration of the noble metal salt solution is 0.01 to 0.1mol. L-1 .
相比于电化学沉积法，本发明利用自然的氧化还原反应得到的贵金属尺寸均一，分布均匀，所述氧化还原反应的温度为室温(15～37℃)，反应时间为1～24h。Compared with the electrochemical deposition method, the present invention utilizes the natural redox reaction to obtain the noble metal with uniform size and uniform distribution, the temperature of the redox reaction is room temperature (15-37°C), and the reaction time is 1-24h.
为保持贵金属/竖直生长的水滑石纳米片的良好物化性质，优选的，所述干燥为真空干燥，温度为40～65℃，干燥时间为4～6h。In order to maintain good physical and chemical properties of the noble metal/vertically grown hydrotalcite nanosheets, preferably, the drying is vacuum drying at a temperature of 40-65° C. and a drying time of 4-6 hours.
该步骤将得到的LDH材料放置在贵金属盐溶液中，通过贵金属与LDH活泼金属之间的氧化还原反应，可以使贵金属颗粒在LDH表面发生还原反应，还原后的贵金属颗粒在LDH表面分布均匀，直径在2.2～2.8nm之间，极大的增加了贵金属的电化学活性表面积。同时通过氧化还原反应固定在LDH表面的贵金属颗粒，与LDH之间有很强的相互作用，减少了在催化甲醇氧化过程中的团聚现象的发生，使贵金属催化的持久性和稳定性得到极大提高。In this step, the obtained LDH material is placed in a noble metal salt solution. Through the redox reaction between the noble metal and the LDH active metal, the noble metal particles can undergo a reduction reaction on the surface of the LDH, and the reduced noble metal particles are evenly distributed on the surface of the LDH. Between 2.2 and 2.8nm, the electrochemically active surface area of noble metals is greatly increased. At the same time, the noble metal particles immobilized on the surface of LDH through redox reaction have a strong interaction with LDH, which reduces the occurrence of agglomeration in the catalytic methanol oxidation process, and greatly improves the durability and stability of noble metal catalysis. improve.
为克服现有技术中甲醇燃料电池催化剂的不足，本发明的第二个目的是提供一种采用上述方法制备得到的贵金属/竖直生长水滑石纳米片。该纳米片在模板表面上呈现竖直生长片的状态，纳米片层分布均匀，厚度均一，为45～55nm(优选50nm)；在纳米片上均匀固定着贵金属颗粒，该贵金属颗粒分布均匀、尺寸均一，粒径为2.2～2.8nm。In order to overcome the shortcomings of methanol fuel cell catalysts in the prior art, the second object of the present invention is to provide a noble metal/vertically grown hydrotalcite nanosheet prepared by the above method. The nanosheets are in the state of vertically growing sheets on the surface of the template, and the nanosheets are evenly distributed and have a uniform thickness of 45-55nm (preferably 50nm); noble metal particles are evenly fixed on the nanosheets, and the noble metal particles are evenly distributed and uniform in size , the particle size is 2.2-2.8nm.
催化剂比表面积受催化剂粒度(贵金属颗粒)控制，通过本发明的氧化还原方法得到的尺寸均一的2.2～2.8nm贵金属颗粒与层状金属材料协同作用，能够明显提高对甲醇氧化的催化能力。The specific surface area of the catalyst is controlled by the particle size of the catalyst (noble metal particles). The 2.2-2.8nm noble metal particles with uniform size obtained by the redox method of the present invention cooperate with the layered metal material to significantly improve the catalytic ability for methanol oxidation.
为克服现有技术中甲醇染料电池催化剂的不足，本发明的第三个目的是提供上述贵金属/竖直生长水滑石纳米片在制备甲醇燃料电池催化剂中的应用。在应用时，将整个具有纳米片的模板用于甲醇燃料电池中。In order to overcome the shortcomings of methanol dye cell catalysts in the prior art, the third object of the present invention is to provide the application of the above noble metal/vertically grown hydrotalcite nanosheets in the preparation of methanol fuel cell catalysts. In application, the entire template with nanosheets is used in a methanol fuel cell.
与现有技术相比，本发明的有益效果是：Compared with prior art, the beneficial effect of the present invention is:
(1)利用本发明中的方法形成的贵金属载体LDH纳米片，在模板材料表面竖直生长，为贵金属催化剂的负载提供了更大的比表面积，并且在模板材料上生长的LDH具有更好的刚性结构。(1) The noble metal carrier LDH nanosheets formed by the method of the present invention grow vertically on the surface of the template material, providing a larger specific surface area for the loading of the noble metal catalyst, and the LDH grown on the template material has better rigid structure.
同时，本发明制备的LDH作为一种层状金属材料与贵金属之间的协同作用增强了贵金属抗CO毒性，提高了贵金属催化剂的稳定性，从而增加了复合催化剂的使用寿命。At the same time, the synergistic effect between the LDH prepared by the invention as a layered metal material and the noble metal enhances the resistance of the noble metal to CO toxicity, improves the stability of the noble metal catalyst, and thus increases the service life of the composite catalyst.
(2)利用氧化还原反应得到的贵金属颗粒尺寸均一(2.2～2.8nm)、分布均匀，暴漏出更大的电化学活性表面积，明显提高了贵金属催化剂对甲醇氧化的催化能力。(2) The noble metal particles obtained by the oxidation-reduction reaction are uniform in size (2.2-2.8nm) and evenly distributed, exposing a larger electrochemically active surface area, which significantly improves the catalytic ability of the noble metal catalyst for methanol oxidation.
(3)本发明合成方法简单易操作，制备所需温度温和，优于传统的甲醇燃料电池催化剂操作步骤，同时贵金属盐溶液可以重复使用极大降低了使用成本。(3) The synthesis method of the present invention is simple and easy to operate, and the temperature required for the preparation is mild, which is superior to the traditional methanol fuel cell catalyst operation steps. At the same time, the noble metal salt solution can be reused, which greatly reduces the use cost.
本发明所涉及的方法制备得到的纳米片状材料能够极大提高催化剂性能，为解决甲醇燃料电池商业化生产提供了新的思路。The nano sheet material prepared by the method involved in the invention can greatly improve the performance of the catalyst, and provides a new idea for solving the commercial production of the methanol fuel cell.
附图说明Description of drawings
图1为贵金属/竖直生长LDH纳米片的制备流程示意图；Fig. 1 is a schematic diagram of the preparation process of noble metal/vertically grown LDH nanosheets;
图2为贵金属/竖直生长LDH纳米片的SEM表征图；Fig. 2 is the SEM characterization figure of noble metal/vertical growth LDH nanosheet;
图3为贵金属/竖直生长LDH纳米片在0.5mol﹒L-1甲醇和1.0mol﹒L-1氢氧化钠混合溶液中的循环伏安曲线。Figure 3 shows the noble metal/vertically grown LDH nanosheets at 0.5mol. L-1 methanol and 1.0mol. Cyclic voltammetry curve in L-1 sodium hydroxide mixed solution.
具体实施方式detailed description
应该指出，以下详细说明都是示例性的，旨在对本发明提供进一步的说明。除非另有指明，本文使用的所有技术和科学术语具有与本发明所属技术领域的普通技术人员通常理解的相同含义。It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
需要注意的是，这里所使用的术语仅是为了描述具体实施方式，而非意图限制根据本发明的示例性实施方式。如在这里所使用的，除非上下文另外明确指出，否则单数形式也意图包括复数形式，此外，还应当理解的是，当在本说明书中使用术语“包含”和/或“包括”时，其指明存在特征、步骤和/或它们的组合。It should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps and/or combinations thereof.
术语解释：Explanation of terms:
竖直：当一个物体只处于“上-下”方向排成直线时，被称为竖直。本发明中的竖直生长是指：在模板表面上，水滑石呈现竖直生长的纳米片状态。Vertical: When an object is only aligned in the "up-down" direction, it is said to be vertical. The vertical growth in the present invention means: on the surface of the template, the hydrotalcite presents a state of vertically growing nanosheets.
室温：其指的是室内温度，本发明的室温范围是15～37℃。Room temperature: it refers to the room temperature, and the range of room temperature in the present invention is 15-37°C.
正如背景技术所介绍的，现有技术中的甲醇燃料电池催化剂存在中间产物CO容易吸附贵金属表面、贵金属催化剂容易发生聚集、以及催化剂制备方法复杂等问题，为了解决如上的技术问题，本发明提出了一种贵金属/竖直生长水滑石纳米片的制备方法，包括以下步骤：As introduced in the background technology, methanol fuel cell catalysts in the prior art have problems such as the intermediate product CO is easy to adsorb on the surface of noble metals, the noble metal catalysts are prone to aggregation, and the preparation method of the catalyst is complicated. In order to solve the above technical problems, the present invention proposes A preparation method of noble metal/vertically growing hydrotalcite nanosheets, comprising the following steps:
(1)将水滑石(LDH)生长所需模板清洗后进行刻蚀，刻蚀后清洗干净；(1) After cleaning the template required for hydrotalcite (LDH) growth, etch it, and clean it after etching;
(2)以甲醇和水的混合溶液作为溶剂，溶解水滑石生长所需要的两种或三种前驱体金属盐和十六烷基三甲基溴化铵(CTAB)，形成均一溶液；(2) Using a mixed solution of methanol and water as a solvent to dissolve two or three precursor metal salts and cetyltrimethylammonium bromide (CTAB) required for hydrotalcite growth to form a homogeneous solution;
(3)将步骤(1)中清洗干净后的模板放入步骤(2)中的均一溶液中，进行水热反应；反应完毕，清洗模板表面并干燥，即得到在模板表面上竖直生长的水滑石纳米片；(3) Put the template cleaned in step (1) into the homogeneous solution in step (2), and carry out hydrothermal reaction; after the reaction is completed, clean the template surface and dry it to obtain the vertical growth on the template surface Hydrotalcite nanosheets;
(4)将步骤(3)中的在模板表面上竖直生长的水滑石纳米片放置在贵金属盐溶液中，进行氧化还原反应，反应完毕后清洗、干燥即得到贵金属/竖直生长水滑石纳米片。(4) Place the hydrotalcite nanosheets grown vertically on the surface of the template in step (3) in a noble metal salt solution to carry out a redox reaction. After the reaction is completed, wash and dry to obtain noble metal/vertically grown hydrotalcite nanosheets. piece.
步骤(1)和(2)的顺序可互调。The order of steps (1) and (2) is interchangeable.
在本发明的一些具体实施方式中，步骤(1)的具体方法，包括：将水滑石生长所需模板用丙酮彻底清洗，并用盐酸溶液进行刻蚀，刻蚀后用无水乙醇以及二次水清洗，至彻底清洗干净。In some specific embodiments of the present invention, the specific method of step (1) includes: thoroughly cleaning the template required for hydrotalcite growth with acetone, and etching with hydrochloric acid solution, and using absolute ethanol and secondary water after etching Rinse until thoroughly cleaned.
在本发明的另一些具体实施方式中，步骤(2)中，所述前驱体金属盐为镍盐、钴盐、铁盐、铝盐、镁盐、锌盐的两种或三种。两种摩尔比例为1:3～1:8，三种摩尔比例为1:3:5～1:8:10。所述甲醇和水的体积比例为5:1～3:1，混合溶剂的种类以及比例对本发明产物的形成具有重要的影响，采用此体积比例的甲醇和水的混合溶剂能够形成性质稳定且分散均匀的水滑石纳米片。In other specific embodiments of the present invention, in step (2), the precursor metal salt is two or three of nickel salt, cobalt salt, iron salt, aluminum salt, magnesium salt, and zinc salt. The two molar ratios are 1:3 to 1:8, and the three molar ratios are 1:3:5 to 1:8:10. The volume ratio of methanol and water is 5:1 to 3:1. The type and ratio of the mixed solvent have an important influence on the formation of the product of the present invention. The mixed solvent of methanol and water in this volume ratio can form a stable and dispersed solvent. Uniform hydrotalcite nanosheets.
在本发明的再一些具体实施方式中，步骤(3)中，所述水热反应的温度为120～200℃，反应时间为12～24h。水热反应温度对本发明产物的形成具有重要的影响，水热反应温度过低，并不能形成纳米片形貌。水热反应温度过高，不仅浪费能源，同时纳米片的尺寸还有所降低，不利于形成理性形貌的水滑石纳米片。In still some specific embodiments of the present invention, in step (3), the temperature of the hydrothermal reaction is 120-200° C., and the reaction time is 12-24 hours. The hydrothermal reaction temperature has an important influence on the formation of the product of the present invention, and the hydrothermal reaction temperature is too low to form nanosheet morphology. Excessively high hydrothermal reaction temperature not only wastes energy, but also reduces the size of nanosheets, which is not conducive to the formation of rationally shaped hydrotalcite nanosheets.
在本发明的又一些具体实施方式中，步骤(4)中，所述贵金属盐为Pt盐、Ru盐、Au盐或其他贵金属盐中的一种或多种，具体可为Na2PtCl6，RuCl3·3H2O，HAuCl4·4H2O等。在碱性环境中进行氧化还原反应，其pH为7～11，浓度为0.01～0.1mol﹒L-1。In some other specific embodiments of the present invention, in step (4), the noble metal salt is one or more of Pt salt, Ru salt, Au salt or other noble metal salts, specifically Na2 PtCl6 , RuCl3 ·3H2 O, HAuCl4 ·4H2 O, etc. Carry out redox reaction in alkaline environment, its pH is 7~11, concentration is 0.01~0.1mol. L-1 .
通过以上方法制备得到的贵金属/竖直生长水滑石纳米片在模板表面上呈现竖直生长片的状态，纳米片层分布均匀，厚度均一，为45～55nm(优选50nm)；在纳米片上均匀分散着贵金属颗粒，由于是采用自然的氧化还原反应将贵金属盐溶液还原得到，所以，贵金属在纳米片的附着力较强，不易散落，该贵金属颗粒分布均匀、尺寸均一，粒径为2.2～2.8nm。The noble metal/vertical growth hydrotalcite nanosheets prepared by the above method present the state of vertical growth sheets on the surface of the template, the nanosheets are evenly distributed, and the thickness is uniform, which is 45-55nm (preferably 50nm); uniformly dispersed on the nanosheets The precious metal particles are obtained by reducing the precious metal salt solution by natural oxidation-reduction reaction, so the precious metal has strong adhesion on the nanosheet and is not easy to scatter. The precious metal particles are evenly distributed and uniform in size, with a particle size of 2.2-2.8nm .
为了使得本领域技术人员能够更加清楚地了解本发明的技术方案，以下将结合具体的实施例与对比例详细说明本发明的技术方案。In order to enable those skilled in the art to understand the technical solution of the present invention more clearly, the technical solution of the present invention will be described in detail below in conjunction with specific examples and comparative examples.
实施例1Example 1
一种贵金属/竖直生长水滑石纳米片甲醇燃料电池催化剂的制备方法意图参见图1，详细的制备步骤如下：首先将碳纤维布(CFP)裁剪成0.5×3cm，用250mL丙酮溶液分五次清洗，去掉表面附着油污，用0.5mol﹒L-1的盐酸刻蚀15min后，用无水乙醇以及二次水清洗6次。然后以5:1的摩尔比称取Ni(NO3)2﹒6H2O(0.2mL 0.2M)与Co(NO3)2﹒6H2O(0.04mL0.2M)，加入1.5g的CTAB，以60mL甲醇和12mL去离子水的混合溶液(体积比：5:1)作为溶剂进行溶解并形成均一溶液。将上述溶液以及LDH模板转移至100mL反应釜，以200℃反应24h后，自然降温，用乙醇和二次水清洗表面。转移至真空干燥箱中，55℃干燥4h，干燥后即得到竖直生长的NiCo LDH纳米片。A schematic diagram of a preparation method of a noble metal/vertically grown hydrotalcite nanosheet methanol fuel cell catalyst is shown in Figure 1. The detailed preparation steps are as follows: first, cut the carbon fiber cloth (CFP) into 0.5×3cm, and wash it five times with 250mL acetone solution , Remove the oil attached to the surface, use 0.5mol﹐ After L-1 hydrochloric acid etching for 15 minutes, wash with absolute ethanol and secondary water for 6 times. Then weigh Ni(NO3 )2 at a molar ratio of 5:1. 6H2 O (0.2mL 0.2M) and Co(NO3 )2 . 6H2 O (0.04mL0.2M), 1.5g of CTAB was added, and a mixed solution of 60mL of methanol and 12mL of deionized water (volume ratio: 5:1) was used as a solvent to dissolve and form a uniform solution. The above solution and LDH template were transferred to a 100mL reactor, reacted at 200°C for 24h, cooled down naturally, and cleaned the surface with ethanol and secondary water. Transfer to a vacuum drying oven and dry at 55°C for 4h, and then vertically grown NiCo LDH nanosheets were obtained after drying.
利用扫描电子显微镜如图2所示，可以观察到，采用本发明所涉及的制备方法所得到的LDH纳米片，在模板表面呈现竖直生长片的特殊形貌，并且纳米片层分布均匀，厚度均一，为50nm。随后将得到的LDH放置在0.05mol﹒L-1Na2PtCl6溶液中(pH＝10)中室温静置12h，再转移至0.05mol﹒L-1RuCl3·3H2O(pH＝11)中静置12h，取出模板，然后进行真空干燥，温度为45℃，干燥时间为6h，即得到PtRu/NiCo LDH-CFP复合催化剂。PtRu/NiCo LDH-CFP复合催化剂中的LDH纳米片上均匀固定着贵金属颗粒，该贵金属颗粒分布均匀、尺寸均一，粒径为2.2～2.8nm。Using a scanning electron microscope as shown in Figure 2, it can be observed that the LDH nanosheets obtained by the preparation method of the present invention present a special morphology of vertical growth sheets on the surface of the template, and the nanosheets are evenly distributed and the thickness Uniform, 50nm. Then the obtained LDH was placed in 0.05mol. L-1 Na2 PtCl6 solution (pH = 10) at room temperature for 12h, then transferred to 0.05mol. After standing in L-1 RuCl3 ·3H2 O (pH=11) for 12 hours, the template was taken out, and then vacuum-dried at 45° C. for 6 hours to obtain a PtRu/NiCo LDH-CFP composite catalyst. Noble metal particles are evenly fixed on the LDH nanosheets in the PtRu/NiCo LDH-CFP composite catalyst, and the noble metal particles are evenly distributed and uniform in size, with a particle size of 2.2-2.8nm.
如图3所示，将制备的PtRu/LDH-CFP复合催化剂，在1.0M CH3OH+0.5M NaOH中，利用循环伏安法扫描，经计算可以看出采用本发明所涉及的方法得到的PtRu/LDH-CFP复合催化剂对甲醇有很好的催化性能，试验重复多次，测得其对甲醇氧化的氧化峰电流密度为32mA·cm-2，相比于现有技术中的常规方法提高1.2～2倍。As shown in Figure 3, the prepared PtRu/LDH-CFP composite catalyst is scanned by cyclic voltammetry in 1.0M CH3 OH+0.5M NaOH, and it can be seen through calculation that the obtained by the method involved in the present invention The PtRu/LDH-CFP composite catalyst has good catalytic performance for methanol. The test was repeated many times, and the oxidation peak current density for methanol oxidation was measured to be 32mA·cm-2 , which is higher than that of conventional methods in the prior art. 1.2 to 2 times.
实施例2Example 2
一种贵金属/竖直生长水滑石纳米片甲醇燃料电池催化剂的制备方法，首先将碳纤维布泡沫镍(NF)裁剪成0.5×3cm，用200mL丙酮溶液分四次清洗，去掉表面附着油污，用2.0mol·L-1的盐酸刻蚀20min后，用无水乙醇以及二次水清洗6次。然后以1:3的摩尔比称取(CH3COO)2Ni﹒4H2O(0.2mL,0.2M)和Fe(NO3)3﹒9H2O(0.6mL,0.2M)，加入3g的十六烷基三甲基溴化铵(CTAB)，以48mL甲醇和12mL去离子水的混合溶液(体积比：4:1)作为溶剂进行溶解并形成均一溶液。将上述溶液以及LDH模板转移至100mL反应釜，以180℃反应12h后，自然降温，用乙醇和二次水清洗表面。转移至真空干燥箱中，40℃干燥6h，干燥后得到竖直生长的NiFe LDH纳米片。将得到的LDH放置在0.01mol﹒L-1RuCl3·3H2O(pH＝11)中室温静置18h，取出模板，然后进行真空干燥，温度为50℃，干燥时间为5h，即得到Ru/NiFe LDH-NF复合催化剂。Ru/NiFe LDH-NF复合催化剂中的LDH纳米片在模板表面上呈现竖直生长片的状态，纳米片层分布均匀，厚度均一，为50nm；在纳米片上均匀固定着贵金属颗粒，该贵金属颗粒分布均匀、尺寸均一，粒径为2.2～2.8nm。A kind of preparation method of noble metal/vertical growth hydrotalcite nano sheet methanol fuel cell catalyst, first cut the carbon fiber cloth nickel foam (NF) into 0.5 * 3cm, wash with 200mL acetone solution in four times, remove the oil stain on the surface, use 2.0 After etching with mol·L-1 hydrochloric acid for 20 min, wash with absolute ethanol and secondary water for 6 times. Then weigh (CH3 COO)2 Ni with a molar ratio of 1:3. 4H2 O (0.2mL, 0.2M) and Fe(NO3 )3 . 9H2 O (0.6mL, 0.2M), adding 3g of cetyltrimethylammonium bromide (CTAB), using a mixed solution of 48mL methanol and 12mL deionized water (volume ratio: 4:1) as a solvent Dissolved and formed a homogeneous solution. The above solution and LDH template were transferred to a 100mL reactor, reacted at 180°C for 12h, cooled down naturally, and cleaned the surface with ethanol and secondary water. Transfer to a vacuum drying oven and dry at 40°C for 6h, and vertically grown NiFe LDH nanosheets were obtained after drying. Place the obtained LDH at 0.01mol. L-1 RuCl3 ·3H2 O (pH=11) was left at room temperature for 18 hours, the template was taken out, and then vacuum-dried at a temperature of 50°C for 5 hours to obtain a Ru/NiFe LDH-NF composite catalyst. The LDH nanosheets in the Ru/NiFe LDH-NF composite catalyst present a state of vertical growth sheets on the surface of the template, and the nanosheets are uniformly distributed and have a uniform thickness of 50nm; noble metal particles are evenly fixed on the nanosheets, and the noble metal particles are distributed Uniform and uniform in size, the particle size is 2.2-2.8nm.
本实施例得到的Ru/NiFe LDH-NF复合催化剂对甲醇有很好的催化性能，测得其对甲醇氧化的氧化峰电流密度较高，相比于现有技术中的常规方法提高1.2～2倍。The Ru/NiFe LDH-NF composite catalyst obtained in this example has good catalytic performance for methanol, and its oxidation peak current density for methanol oxidation is measured to be higher, which is 1.2-2 times higher than that of conventional methods in the prior art. times.
实施例3Example 3
一种贵金属/竖直生长水滑石纳米片甲醇燃料电池催化剂的制备方法，首先将碳纸(CP)裁剪成0.5×3cm，用200mL丙酮溶液分四次清洗，去掉表面附着油污，用2.5mol·L-1的盐酸刻蚀10min后，用无水乙醇以及二次水清洗6次。然后以1:3:8的摩尔比称取Al(NO3)3﹒9H2O(0.2mL,0.2M)、Mg(NO3)2﹒6H2O(0.6mL,0.2M)和Zn(NO3)2﹒6H2O(1.6mL,0.2M)，加入4.5g的十六烷基三甲基溴化铵(CTAB)，以54mL甲醇和12mL去离子水的混合溶液(体积比：4.5:1)作为溶剂进行溶解并形成均一溶液。将上述溶液以及LDH模板转移至100mL反应釜，以200℃反应20h后，自然降温，用乙醇和二次水清洗表面。转移至真空干燥箱中，45℃干燥5h干燥后得到竖直生长的LDH纳米片。将得到的LDH放置在0.1mol﹒L-1Na2PtCl6溶液中室温(pH＝10)中静置12h，取出模板，然后进行真空干燥，温度为65℃，干燥时间为4h，即得到Pt/NiFeLDH-CP复合催化剂。Pt/NiFe LDH-CP复合催化剂中的LDH纳米片在模板表面上呈现竖直生长片的状态，纳米片层分布均匀，厚度均一，为50nm；在纳米片上均匀固定着贵金属颗粒，该贵金属颗粒分布均匀、尺寸均一，粒径为2.2～2.8nm。A preparation method of noble metal/vertical growth hydrotalcite nanosheet methanol fuel cell catalyst, first cut carbon paper (CP) into 0.5 × 3cm, wash it with 200mL acetone solution four times, remove the oil stain on the surface, and use 2.5mol· After etching with L-1 hydrochloric acid for 10 min, wash with absolute ethanol and secondary water for 6 times. Then weigh Al(NO3 )3 at a molar ratio of 1:3:8. 9H2 O (0.2mL, 0.2M), Mg(NO3 )2 . 6H2 O (0.6mL, 0.2M) and Zn(NO3 )2 . 6H2 O (1.6mL, 0.2M), add 4.5g of cetyltrimethylammonium bromide (CTAB), and use a mixed solution of 54mL of methanol and 12mL of deionized water (volume ratio: 4.5:1) as a solvent Dissolution occurs and a homogeneous solution is formed. The above solution and LDH template were transferred to a 100mL reactor, reacted at 200°C for 20h, cooled down naturally, and cleaned the surface with ethanol and secondary water. Transfer to a vacuum oven and dry at 45°C for 5 hours to obtain vertically grown LDH nanosheets. Place the obtained LDH at 0.1mol. The L-1 Na2 PtCl6 solution was left at room temperature (pH=10) for 12 hours, the template was taken out, and then vacuum-dried at a temperature of 65°C for 4 hours to obtain a Pt/NiFeLDH-CP composite catalyst. The LDH nanosheets in the Pt/NiFe LDH-CP composite catalyst present a state of vertical growth sheets on the surface of the template, and the nanosheets are evenly distributed and have a uniform thickness of 50nm; noble metal particles are evenly fixed on the nanosheets, and the noble metal particles are distributed Uniform and uniform in size, the particle size is 2.2-2.8nm.
本实施例得到的Pt/NiFe LDH-CP复合催化剂对甲醇有很好的催化性能，测得其对甲醇氧化的氧化峰电流密度较高，相比于现有技术中的常规方法提高1.2～2倍。The Pt/NiFe LDH-CP composite catalyst obtained in this example has good catalytic performance for methanol, and its oxidation peak current density for methanol oxidation is measured to be higher, which is 1.2-2 times higher than that of conventional methods in the prior art. times.
上述实施例为本发明较佳的实施方式，但本发明的实施方式并不受上述实施例的限制，其他的任何未背离本发明的精神实质与原理下所作的改变、修饰、替代、组合、简化，均应为等效的置换方式，都包含在本发明的保护范围之内。The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.
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| CN201710099791.1ACN106784881B (en) | 2017-02-23 | 2017-02-23 | A kind of noble metal/vertical growth hydrotalcite nano piece methanol fuel cell catalyst and preparation method thereof |
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