Atomic-scale Ag cluster functionalized MOF-based composite electrocatalyst as well as preparation method and application thereof

Abstract

The invention provides an atomic-scale Ag cluster functionalized MOF (Metal Organic Framework)-based composite electrocatalyst as well as a preparation method and application thereof. The catalyst is named as Ag (at) MOF-Ag4-2Ph. The catalyst is prepared by a one-step method at room temperature, and the specific steps are as follows: stirring a mixed solution of a triazole derived ligand, silver nitrate and ammonia water at 25 DEG C, centrifuging the reaction solution after the reaction is finished, and performing vacuum drying to obtain the electrocatalyst. The catalyst has superfine Ag nano-particles generated by triazole derived ligands in situ, Ag monatomic and Ag4 atomic cluster active sites, and the three components have a synergistic effect, so that excellent electrocatalytic CO2 reduction activity is realized. The catalyst can realize full-pH electrolysis and maintain high selectivity and high current density to CO in an extremely wide voltage range. The method is an Ag-based industrial-grade high-performance electrocatalyst which is green, simple and convenient to synthesize and easy to produce on a large scale, a green example is established for an industrial CO2 electrolysis system, and the method has important practical application value in the aspects of industrial flue gas CO2 recovery and the like.

Description

Technical Field

[0001] This invention belongs to the field of MOF-based composite electrocatalysts; in particular, it relates to an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, its preparation method, and its application. Background Technology

[0002] Electrocatalytic carbon dioxide reduction (ECO2RR) is a promising technology that uses renewable electricity to convert ECO2RR into high-value-added chemicals and fuels, and has therefore attracted widespread attention. Carbon monoxide (CO), as one of the most important products of ECO2RR, can be used in the Fischer-Tropsch process for the industrial synthesis of high-value hydrocarbon fuels, thus possessing significant research value.

[0003] Based on this, a large amount of research has focused on developing electrocatalysts with high selectivity and stability, as well as optimizing electrolysis systems to meet the needs of industrial applications. Among the noble metal catalysts reported for ECO2RR, Pd, Au, and Ag-based catalysts are widely considered to have high activity and selectivity for CO production. Compared with the other two noble metals, Ag-based catalysts have greater commercial application prospects due to their low cost and high abundance. However, currently available commercial Ag-based electrocatalysts are not only expensive, but also fail to meet long-term stability and high selectivity requirements in practical applications, and suffer from significant energy losses. In addition, many Ag-based catalysts currently under research are typically complex to synthesize, costly, and cannot be prepared in large quantities in a green manner. Furthermore, their catalytic stability does not meet the requirements for practical applications, and their effective CO2 conversion efficiency is low, which greatly limits their industrial application.

[0004] Therefore, it is necessary to develop a novel Ag-based catalyst that is simple, inexpensive, stable, energy efficient, and highly selective to meet the needs of practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, its preparation method, and its application.

[0006] This invention is achieved through the following technical solution:

[0007] This invention relates to an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, named Ag@MOF-Ag4-2Ph electrocatalyst.

[0008] This invention also relates to a method for preparing the aforementioned atomically Ag cluster-functionalized MOF-based composite electrocatalyst, comprising the following steps:

[0009] Step 1: Triazole-derived ligand, silver nitrate, and ammonia were mixed in a specific ratio and added to a reaction flask. The mixture was stirred at room temperature to obtain the MOF-based composite electrocatalyst, Ag@MOF-Ag4-2Ph. The reaction equation is as follows:

[0010]

[0011] Step 2: The catalyst is then centrifuged and vacuum dried to obtain a powdered MOF-based composite electrocatalyst.

[0012] Preferably, in step 1, the ligand is a triazole-derived ligand.

[0013] Preferably, the structural formula of the triazole-derived ligand is shown in (I):

[0014]

[0015] Preferably, in step 1, the ratio of the amount of ligand, silver nitrate and ammonia (28%) is (1-5):(1.4-1.5):(3-20).

[0016] Preferably, in step 1, the room temperature is 25°C, and the stirring time is 0.1 to 1 hour.

[0017] The present invention has the following advantages:

[0018] (1) The catalyst preparation method involved in this invention is not only green and simple, but also rapid and can meet the requirements of large-scale synthesis to obtain gram-level industrial-grade high-performance Ag-based electrocatalysts. In addition, the method involved in this invention can effectively control the size of the catalyst to achieve a nanoscale state (50-100nm), thereby improving the selectivity of electrocatalytic CO2 to CO. This method does not require additional mechanical force, heating or harsh reaction conditions, and its reaction environment is friendly. Compared with existing commercial electrocatalysts, it is low in cost and easy to obtain.

[0019] (2) The catalyst involved in this invention is a highly efficient industrial-grade electrocatalyst that is reported for the first time, surpassing most advanced Ag-based and non-Ag-based electrocatalysts;

[0020] Compared with the most advanced existing Ag-based and non-Ag-based electrocatalysts, the catalyst of this invention not only maintains high performance over an extremely wide voltage range, but also performs well in all-pH electrolysis and FE electrolysis. CO j CO The catalyst exhibits high levels of cathode energy efficiency (CEE) and stability. Under alkaline conditions, the catalyst of this invention possesses high FE... CO (>90%) and j CO The voltage range (for industrial-grade current density) is the widest among all the literature.

[0021] The specific performance advantages of the catalyst of this invention are as follows:

[0022] ① Under alkaline conditions, within an ultra-wide voltage range of -0.3V to -1.9V (vs. RHE), the average Faraday efficiency (FE) for CO is... CO Nearly 99%; at -2.0V FE CO The current density remains high, approaching 96%, with a total current density reaching 1.2 A cm⁻¹. -2 The maximum CO partial current density can reach 1.09 A cm⁻¹. -2 It meets industrial application standards.

[0023] ② Under neutral conditions, the average FE ranges from -1.2V to -2.1V (vs. RHE). CO It can reach around 98%, j CO 273mA cm -2 No liquid products were detected during electrolysis, demonstrating its excellent CO selectivity.

[0024] ③ Under acidic conditions, a small amount of formic acid will be produced in the range of -0.9V to -1.8V (vs. RHE), but the average FE will still be maintained. CO >90% (up to 97%), j CO 212mA cm -2 .

[0025] (3) The catalyst of the present invention is the first to use triazole-derived ligands to directly reduce Ag(I) in situ to ultrafine atomically precise Ag NPs, and can control their size change, thereby precisely regulating the performance of electrocatalytic CO2 reduction. Compared with the traditional Ag NP synthesis method, the present invention does not require the addition of additional reducing agents (such as NaHB4), and can achieve the controllable preparation of highly active Ag NPs under mild conditions, which not only reduces the synthesis steps, but also greatly reduces the cost.

[0026] (4) The catalyst of the present invention is extremely stable, resistant to strong acids and strong bases, and has strong hydrophobicity. It can also be continuously electrolyzed for about 35 hours under different pH conditions. The catalyst structure and activity remain unchanged before and after the reaction.

[0027] (5) The catalyst of the present invention contains ultrafine Ag nanoparticles (minimum size 1.4 nm, average size 2.4 nm) generated in situ in one step by triazole-derived ligands, and triple active sites constructed by Ag single atoms and Ag4 atom clusters. The triple sites work synergistically to achieve efficient promotion of electrocatalytic CO2 to CO. In the active sites, Ag NPs promote CO2 proton-electron coupling transfer through electron-rich states; Ag4 atom clusters and Ag single atoms work synergistically to reduce the energy barrier for *COOH formation, while Ag4 accelerates H2O decomposition and enhances proton adsorption, while Ag single atom sites weaken *CO intermediate adsorption, synergistically promoting CO generation and inhibiting the formic acid pathway and HER, and efficiently driving ECO2RR.

[0028] (6) The catalyst of the present invention can be prepared in batches by using different amounts of ligands; by using different stirring times, the loading of Ag NPs and the size change of the catalyst can be controlled, so that the catalyst can achieve the best catalytic effect. Attached Figure Description

[0029] Figure 1 The images show the electron microscopy results of the electrocatalyst prepared in Example 1 before and after the reaction; where (a, b, c) are transmission electron microscope images before the reaction, (d, e, f) are spherical aberration electron microscope images before the reaction; (g) is a transmission electron microscope image after the reaction under alkaline electrolyte conditions; (h) is a transmission electron microscope image after the reaction under neutral electrolyte conditions; and (k) is a transmission electron microscope image after the reaction under acidic electrolyte conditions.

[0030] Figure 2 The following figures show the electrocatalytic performance test results of the electrocatalyst prepared in Example 1 under different conditions: (a) electrocatalytic performance under alkaline electrolyte conditions; (b) electrocatalytic performance under neutral electrolyte conditions; (c) electrocatalytic performance under acidic electrolyte conditions; (d) electrolysis test results of the electrocatalyst under high current; and (e) stability test results of the electrocatalyst under different pH conditions.

[0031] Figure 3 The image shows the in-situ infrared reaction mechanism monitoring results of the electrocatalyst prepared in Example 1.

[0032] Figure 4 Transmission electron microscope (TEM) images of the electrocatalyst prepared for Comparative Example 1 before and after the reaction under different conditions; wherein, (a) TEM image before the reaction; (b) TEM image after the reaction under alkaline electrolyte conditions; (c) TEM image after the reaction under neutral electrolyte conditions; (d) TEM image after the reaction under acidic electrolyte conditions.

[0033] Figure 5Electrocatalytic performance of the electrocatalyst prepared for Comparative Example 1 under different conditions; wherein, (a) electrocatalytic performance under alkaline electrolyte conditions; (b) electrocatalytic performance under neutral electrolyte conditions; (c) electrocatalytic performance under acidic electrolyte conditions;

[0034] Figure 6 Transmission electron microscope (TEM) images of the electrocatalyst prepared for Comparative Example 2 before and after the reaction under different conditions; wherein, (a) TEM image before the reaction; (b) TEM image after the reaction under alkaline electrolyte conditions; (c) TEM image after the reaction under neutral electrolyte conditions; (d) TEM image after the reaction under acidic electrolyte conditions.

[0035] Figure 7 Electrocatalytic performance of the electrocatalyst prepared in Comparative Example 2 under different conditions: (a) electrocatalytic performance under alkaline electrolyte conditions; (b) electrocatalytic performance under neutral electrolyte conditions; (c) electrocatalytic performance under acidic electrolyte conditions.

[0036] Figure 8 The graph shows the electrocatalytic performance of commercial Ag NPs electrocatalysts.

[0037] Figure 9 The graphs show a comparison of the electrocatalysts prepared in Example 1 and Comparative Example 2 in terms of electrocatalytic activity and energy efficiency. Specifically, (a) is the double-layer capacitance (Cdl) graph for Example 1; (b) is the double-layer capacitance (Cdl) graph for Comparative Example 2; (c) is a comparison graph of electrochemical active surface area (ECSA); (d) is a comparison graph of electrochemical impedance spectroscopy (EIS); (e) is a comparison graph of cathode energy efficiency (CEE); and (f) is a comparison graph of turnover frequency (TOF).

[0038] Figure 10 The figures show a comparison of the electrocatalytic performance of Example 1 with the latest published advanced Ag-based electrocatalysts and non-Ag-based electrocatalysts; wherein, (a) is a comparison of the electrocatalytic performance with the latest published advanced Ag-based electrocatalysts; and (b) is a comparison of the electrocatalytic performance with the latest published advanced non-Ag-based electrocatalysts.

[0039] Figure 11 The X-ray diffraction pattern of the Ag@MOF-Ag4-2Ph electrocatalyst prepared in Example 1 of this invention is shown below.

[0040] Figure 12 This is an overall morphology diagram of the Ag@MOF-Ag4-2Ph electrocatalyst prepared in Example 1 of this invention;

[0041] Figure 13 This is a sample image of Ag@MOF-Ag4-2Ph prepared in Example 1 of the present invention. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0043] Example 1

[0044] This embodiment relates to a method for preparing an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, comprising the following steps:

[0045] Step 1: Ligand L1, nitrate, and ammonia were mixed in a specific ratio and added to a beaker. The mixture was stirred at 25°C for 1 hour, and the reaction proceeded immediately to obtain a white powder. The powder was then centrifuged and dried to obtain powdered Ag@MOF-Ag4-2Ph electrocatalyst. The amount of ligand L1 was 1 g, the amount of silver nitrate was 1.5 g, and the amount of ammonia was 10 g.

[0046] The structural formula (I) of ligand L1 is as follows:

[0047]

[0048] Step 2: The electrocatalyst Ag@MOF-Ag4-2Ph prepared in Step 1 was subjected to electrocatalytic CO2RR performance testing, the data were recorded, and the Faraday efficiency (FE) of the electrocatalyst prepared in Step 1 for CO was calculated. CO ) and partial current density (j CO ),See Figure 2 As shown;

[0049] Step 3: Take transmission electron microscope images of the electrocatalyst before and after the reaction. See... Figure 1 , Figure 3 As shown.

[0050] Comparative Example 1

[0051] This embodiment relates to a method for preparing an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, comprising the following steps:

[0052] Step 1: Ligand L1, silver nitrate, and ammonia were mixed in a specific ratio, heated to 105℃, reacted for 3 days, and then centrifuged and dried to obtain powdered Ag@MOF-Ag4-2Ph electrocatalyst; wherein the amount of ligand L1 was 1 mol, the amount of silver nitrate was 1.5 mol, and the amount of ammonia was 10 mol.

[0053] Step 2: The electrocatalyst Ag@MOF-Ag4-2Ph prepared in Step 1 was subjected to electrocatalytic CO2RR performance testing, the data were recorded, and the Faraday efficiency (FE) of the electrocatalyst prepared in Step 1 for CO was calculated. CO ) and partial current density (j CO ),See Figure 4 As shown;

[0054] Step 3: Take transmission electron microscope images of the electrocatalyst before and after the reaction. See... Figure 4 , Figure 5 As shown.

[0055] Comparative Example 2

[0056] This embodiment relates to a method for preparing an atomically Ag cluster-functionalized MOF-based composite electrocatalyst, including the following steps:

[0057] Step 1: Ligand L2, silver nitrate, and ammonia were mixed in a specific ratio and stirred at room temperature for 1 hour to react. A white powder was obtained immediately after the reaction, and then centrifuged and dried to obtain powdered Ag@MOF-2Me electrocatalyst. The amount of ligand L2 was 1 mol; the amount of silver nitrate was 1.5 mol; and the amount of ammonia was 10 mol.

[0058] The structural formula (II) of ligand L2 is as follows:

[0059]

[0060] Step 2: Perform electrocatalytic CO2RR performance testing on the electrocatalyst obtained in Step 1, record the data, and calculate the Faraday efficiency (FE) of the electrocatalyst for CO obtained in Step (1). CO ) and partial current density (j CO ),See Figure 6 As shown;

[0061] Step 3: Take transmission electron microscope images of the above electrocatalyst before and after the reaction, see... Figure 7 As shown.

[0062] test

[0063] Example 1, Comparative Example 1, Comparative Example 2, commercial Ag NPs electrocatalysts, newly published advanced Ag-based electrocatalysts, and non-Ag-based electrocatalysts were used as controls. The results are shown in Tables 1, 2, and 3, respectively. Figure 8 , Figure 9 , Figure 10 As shown.

[0064] Commercial Ag NPs electrocatalysts are available for direct purchase.

[0065] Table 1

[0066]

[0067] As shown in Table 1, combining the data from the Ag@MOF-Ag4-2Ph catalyst obtained in Example 1, the catalysts obtained in Comparative Example 1 and Comparative Example 2, and the electrocatalysis of commercial Ag NPs, it can be found that temperature not only significantly affects the growth size of Ag NPs but also significantly affects the size change of the catalyst, thus significantly affecting the electrocatalytic performance of the catalyst. Therefore, the Ag@MOF-Ag4-2Ph catalyst obtained by stirring at room temperature has a significant effect on the electrocatalytic performance of CO. CO and j CO All achieved optimal results, see Figures 11-13 As shown.

[0068] Table 2

[0069]

[0070] As can be seen from the data in Table 2 above, by comparing the catalyst Ag@MOF-Ag4-2Ph obtained in Example 1 with the latest published advanced Ag-based electrocatalysts, it can be found that Ag@MOF-Ag4-2Ph performs better in all-pH electrolysis and FE... CO j CO The high level of performance in terms of CEE and stability verifies the superiority of the technical solution of this invention and shows great potential for future applications.

[0071] Table 3

[0072]

[0073]

[0074]

[0075] As can be seen from the data in Table 3 above, a comparison between the Ag@MOF-Ag4-2Ph catalyst obtained in Example 1 and the latest published advanced non-Ag-based electrocatalysts reveals that Ag@MOF-Ag4-2Ph can maintain high performance under a wide pH range; in particular, it exhibits high FE under alkaline conditions. CO (>90%) and j CO The voltage range (for industrial-grade current density) is the widest among all the literature. It also has significant advantages under acidic and neutral conditions.

[0076] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An atomically Ag cluster-functionalized MOF-based composite electrocatalyst, characterized in that, It was named Ag@MOF-Ag4-2Ph electrocatalyst.

2. A method for preparing an atomically Ag cluster-functionalized MOF-based composite electrocatalyst as described in claim 1, characterized in that, Includes the following steps: Step 1: The ligand, silver nitrate and ammonia are mixed in a certain proportion and then added to the reaction flask. The mixture is stirred at room temperature to obtain the MOF-based composite electrocatalyst, namely Ag@MOF-Ag4-2Ph electrocatalyst. Step 2: The catalyst is then centrifuged and vacuum dried to obtain a powdered MOF-based composite electrocatalyst.

3. The method for preparing the atomically Ag cluster-functionalized MOF-based composite electrocatalyst as described in claim 2, characterized in that, In step 1, the ligand is a triazole-derived ligand.

4. The method for preparing the atomically Ag cluster-functionalized MOF-based composite electrocatalyst as described in claim 3, characterized in that, The structural formula of the triazole-derived ligand is shown in (I):

5. The method for preparing the atomically Ag cluster-functionalized MOF-based composite electrocatalyst as described in claim 2, characterized in that, In step 1, the ratio of the amount of ligand, silver nitrate and ammonia is (1-5):(1.4-1.5):(3-20).

6. The method for preparing the atomically Ag cluster-functionalized MOF-based composite electrocatalyst as described in claim 2, characterized in that, In step 1, the room temperature is 25°C, and the stirring time is 0.1 to 1 hour.

7. The application of a MOF-based composite electrocatalyst functionalized with atomic-level Ag clusters as described in claim 1, characterized in that, Application of this electrocatalyst in the efficient electrocatalytic reduction of CO2 to CO.

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