Preparation method of hydrophobic phthalocyanine ionic liquid gel electrode capable of being used for electrocatalytic nitrogen reduction

Abstract

The invention belongs to the technical field of electrode preparation, and particularly relates to a preparation method of a hydrophobic phthalocyanine ionic liquid gel electrode capable of being used for electrocatalytic nitrogen reduction. The preparation method comprises the following steps: dissolving metal phthalocyanine, a hydrophobic polymerizable ionic liquid monomer and a photoinitiator into liquid hydrophobic ionic liquid, and putting the solution and an electrode substrate into a mold together; polymerizable ionic liquid monomers are polymerized through a photo-initiation polymerization method, and the hydrophobic metal phthalocyanine ionic liquid gel electrode with polyionic liquid as a gel network skeleton is formed. The ionic liquid gel in the electrode can enable the electrode to keep good conductivity, more importantly, the ionic liquid gel is a dispersing agent of phthalocyanine, phthalocyanine molecules in the electrode exist in the ionic liquid gel in a monodisperse form, the catalytic performance of the phthalocyanine molecules is improved, and the electrode has application value in the field of electrocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of electrode preparation technology, and specifically relates to a method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction. Background Technology

[0002] Metal phthalocyanines, containing various transition metals in the +2 valence state, such as Fe, Ni, Cu, Co, and Zn, have wide applications in electrochemical catalysis. Due to the π-π interactions between metal phthalocyanines, the molecules often exist as polymers. This aggregation problem drastically reduces the number of exposed central metals, severely impacting their catalytic efficiency. Summary of the Invention

[0003] This invention utilizes the property of ionic liquids to dissolve phthalocyanines, gelling the ionic liquid containing dissolved metal phthalocyanines to design a hydrophobic phthalocyanine ionic liquid gel electrode suitable for electrocatalytic nitrogen reduction. The metal phthalocyanines are dispersed in the ionic liquid gel, exposing more catalytic active sites. Using carbon cloth or nickel foam as the electrode substrate, an electrode suitable for electrocatalytic nitrogen reduction is prepared. Catalytic performance evaluation shows that the metal phthalocyanines in the ionic liquid gel exhibit higher catalytic performance and Faraday efficiency.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction is prepared by the following steps:

[0006] 1) Using ultrasound, metal phthalocyanine is dissolved in a liquid hydrophobic ionic liquid to form a phthalocyanine hydrophobic ionic liquid solution in which the metal phthalocyanine is monodisperse in the solution, denoted as solution A;

[0007] 2) Using ultrasound, the polymerizable ionic liquid monomer is dissolved in solution A to form a hydrophobic ionic liquid solution containing the polymerizable ionic liquid, denoted as solution B;

[0008] 3) The photoinitiator was dissolved in solution B using ultrasound to obtain a hydrophobic ionic liquid-based ink-like slurry, denoted as solution C;

[0009] 4) Place solution C and the electrode substrate in a mold simultaneously. Under ultraviolet light irradiation, the polymerizable ionic liquid in solution C is photo-initiated to polymerize, thus preparing a hydrophobic phthalocyanine ionic liquid gel electrode in situ.

[0010] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 1), the metal phthalocyanine is any one of iron phthalocyanine and its derivatives, cobalt phthalocyanine and its derivatives, copper phthalocyanine and its derivatives, and nickel phthalocyanine and its derivatives.

[0011] 3. A hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, in step 1), the concentration of metal phthalocyanine in the liquid hydrophobic ionic liquid is 1-2 g / L.

[0012] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 1), the composition of the liquid hydrophobic ionic liquid is: the anion is a hydrophobic anionic group; the cation is an imidazole or pyridine cation.

[0013] Preferably, the anion of the liquid hydrophobic ionic liquid is a bis(trifluoromethanesulfonyl)imine anion or a hexafluorophosphate anion; the cation of the liquid hydrophobic ionic liquid is a 1-butyl-3-methylimidazolium cation, a 1-ethyl-3-ethylimidazolium cation, or an N-ethylpyridine cation.

[0014] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 2), the polymerizable ionic liquid monomer is composed of: anion being a hydrophobic anionic group; and cation being an imidazole cation or a pyridine cation containing a polymerizable group.

[0015] Preferably, the anion of the polymerizable ionic liquid monomer is a bis(trifluoromethanesulfonyl)imine anion or a hexafluorophosphate anion; the cation of the polymerizable ionic liquid monomer is a 1-vinyl-3-methylimidazolium cation, a 1-vinyl-3-ethylimidazolium cation, a 1-vinyl-3-butylimidazolium cation, or an N-vinylpyridine cation.

[0016] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 2), the mass ratio of the polymerizable ionic liquid monomer to solution A is 4:6 to 6:4.

[0017] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 3), the concentration of the photoinitiator in the hydrophobic ionic liquid-based ink-like slurry, i.e., solution C, is 0.05–0.1 g / L.

[0018] Furthermore, in the above-mentioned method for preparing a hydrophobic phthalocyanine ionic liquid gel electrode that can be used for electrocatalytic nitrogen reduction, in step 4), the electrode substrate is nickel foam, copper foam, or carbon cloth.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention uses photo-initiated polymerization to polymerize polymerizable ionic liquids, forming a metal phthalocyanine hydrophobic ionic liquid gel electrode with the polyionic liquid as the gel network framework. The ionic liquid gel in this electrode enables it to maintain good conductivity.

[0021] 2. The hydrophobic phthalocyanine ionic liquid gel electrode of the present invention has excellent catalytic ability of metal phthalocyanine center. Dispersing metal phthalocyanine into a single molecule state using ionic liquid gel is beneficial to improving the efficiency of phthalocyanine center metal in electrocatalytic nitrogen reduction process. In-situ preparation of electrode with electrocatalytic nitrogen reduction function expands the application field of phthalocyanine catalysts and improves their utilization value. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the fabrication process for a hydrophobic phthalocyanine ionic liquid gel electrode.

[0023] Figure 2 This is the UV-Vis absorption spectrum of monodisperse phthalocyanine in a hydrophobic phthalocyanine ionic liquid gel electrode.

[0024] Figure 3 This is a photograph of a hydrophobic phthalocyanine ionic liquid gel electrode.

[0025] Figure 4 The graph shows the electrocatalytic nitrogen reduction performance of the hydrophobic phthalocyanine ionic liquid gel electrode. In the graph, A is the linear sweep voltammetric curve of the gel electrode under N2 and Ar, B is the curve of electrocatalytic current of the gel electrode over time, C is the ammonia yield and faradaic efficiency of the gel electrode at different potentials, and D is the ammonia yield and faradaic efficiency of the gel electrode after 5 reuses at a potential of -0.3V. Detailed Implementation

[0026] To better explain the present invention, the following embodiments are provided for further illustration. It should be understood that the following embodiments are intended to better explain the content of the present invention, and not to limit the scope of protection of the present invention in any way.

[0027] Example 1

[0028] (a) Preparation method (e.g.) Figure 1 )

[0029] 1) Cut 110 PPI nickel foam into 1.5 cm × 1.0 cm pieces, clean and soak in acetone for 10 min under ultrasonic treatment, clean with purified water, soak in 2 mol / L hydrochloric acid for 15 min, ultrasonically clean for 10 min, rinse with ultrapure water until pH neutral, and set aside.

[0030] 2) Weigh 10 mg of iron phthalocyanine using a 1 / 1,000,000 balance and dissolve it in 10 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid using ultrasound. This forms a hydrophobic ionic liquid in which the metal phthalocyanine is monodisperse in the solution, denoted as solution A.

[0031] 3) Using ultrasound, 14 g of 1-vinyl-3-methylimidazolium hexafluorophosphate (of the same mass as solution A) was dissolved in solution A to obtain a hydrophobic phthalocyanine ionic liquid containing a polymerizable ionic liquid, denoted as solution B. The mass ratio of the liquid hydrophobic ionic liquid to the polymerizable ionic liquid monomer in this solution was 5:5.

[0032] 4) Subsequently, 1 mg of Igacure 2959 photoinitiator was added to solution B and sonicated to completely dissolve the initiator, resulting in a hydrophobic ionic liquid, denoted as solution C.

[0033] 5) Place the nickel foam and 0.1 mL of solution C together in the mold groove (1.0 cm × 1.0 cm) and perform photoinitiated polymerization under ultraviolet light for 5 min to form a hydrophobic phthalocyanine ionic liquid gel electrode.

[0034] (II) Application

[0035] A hydrophobic phthalocyanine ionic liquid gel electrode was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. 0.1M Na₂SO₄ was used as the electrolyte, and 0.1M H₂SO₄ was used as the tail gas receiving liquid. Nitrogen gas was introduced into the reaction system for 2 hours. After the reaction was completed, the ammonia content in the electrolyte and tail gas absorption liquid was determined using the indophenol blue method.

[0036] (III) Catalytic performance of electrocatalysis

[0037] like Figure 4 As shown in Figure A, the LSV curve under argon atmosphere is generally above the curve under nitrogen atmosphere, indicating that under the same potential conditions, nitrogen gas detector has a higher current density and electrocatalytic activity. Figure 4 B shows the current-time curves of the gel electrode at five different potentials. Under different potential conditions, the current density showed no significant decay or fluctuation, indicating that the gel electrode exhibits good stability during the electrocatalytic process. Using the indophenol blue method, the ammonia production and Faradaic efficiency were calculated as follows: Figure 4As shown in Figure C, the ammonia production rate reaches 31.50 μg h⁻¹ at -0.3 V. -1 mg cat -1 Faraday efficiency reached 29.80%. Figure 4 D represents the ammonia yield and Faradaic efficiency of the gel electrode after five cycles at a potential of -0.3V. After five catalytic cycles, the ammonia production rate can still be maintained at 30 μg / h. -1 mg cat -1 The Faraday efficiency remained close to 30%, indicating that this type of electrode has good stability in the NRR reaction.

Claims

1. A hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction, characterized in that, Its preparation method includes the following steps: 1) Using ultrasound, metal phthalocyanine is dissolved in a liquid hydrophobic ionic liquid to form a phthalocyanine hydrophobic ionic liquid solution in which the metal phthalocyanine is monodisperse in the solution, denoted as solution A; 2) Using ultrasound, the polymerizable ionic liquid monomer is dissolved in solution A to form a hydrophobic ionic liquid solution containing the polymerizable ionic liquid, denoted as solution B; 3) The photoinitiator was dissolved in solution B using ultrasound to obtain a hydrophobic ionic liquid-based ink-like slurry, denoted as solution C; 4) Place solution C and the electrode substrate in a mold simultaneously. Under ultraviolet light irradiation, the polymerizable ionic liquid in solution C is photo-initiated to polymerize, thus preparing a hydrophobic phthalocyanine ionic liquid gel electrode in situ.

2. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 1), the metal phthalocyanine is any one of iron phthalocyanine and its derivatives, cobalt phthalocyanine and its derivatives, copper phthalocyanine and its derivatives, and nickel phthalocyanine and its derivatives.

3. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 1), the concentration of metal phthalocyanine in the liquid hydrophobic ionic liquid is 1–2 g / L.

4. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 1), the composition of the liquid hydrophobic ionic liquid is as follows: the anion is a hydrophobic anionic group; the cation is an imidazole or pyridine cation.

5. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 4, characterized in that, The anion of the liquid hydrophobic ionic liquid is a bis(trifluoromethanesulfonyl)imine anion or a hexafluorophosphate anion; the cation of the liquid hydrophobic ionic liquid is a 1-butyl-3-methylimidazolium cation, a 1-ethyl-3-ethylimidazolium cation or an N-ethylpyridine cation.

6. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 2), the polymerizable ionic liquid monomer is composed of: anions being hydrophobic anionic groups; and cations being imidazole cations or pyridine cations containing polymerizable groups.

7. A hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 6, characterized in that, The anion of the polymerizable ionic liquid monomer is a bis(trifluoromethanesulfonyl)imine anion or a hexafluorophosphate anion; the cation of the polymerizable ionic liquid monomer is a 1-vinyl-3-methylimidazolium cation, a 1-vinyl-3-ethylimidazolium cation, a 1-vinyl-3-butylimidazolium cation, or an N-vinylpyridine cation.

8. The hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 2), the mass ratio of the polymerizable ionic liquid monomer to solution A is 4:6 to 6:

4.

9. A hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 3), the concentration of the photoinitiator in the hydrophobic ionic liquid-based ink slurry, i.e., solution C, is 0.05–0.1 g / L.

10. A hydrophobic phthalocyanine ionic liquid gel electrode for electrocatalytic nitrogen reduction according to claim 1, characterized in that, In step 4), the electrode substrate is nickel foam, copper foam, or carbon cloth.

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