Preparation method of Mo-doped Ru cluster hydrogen evolution catalyst for inhibiting OH radical poisoning

Abstract

The present invention relates to the field of electrocatalytic materials and aims to provide a method for preparing a Mo-doped Ru cluster hydrogen evolution catalyst that inhibits the poisoning effect of OH radicals. The method comprises: uniformly mixing a nitrogen source, a carbon source, and precursors of metallic molybdenum and ruthenium, and then performing a gradient temperature continuous heat treatment under an inert atmosphere; after naturally cooling to room temperature, a black powdery catalyst product is obtained. The present invention provides a bimetallic atomic-level hydrogen evolution catalyst having a Mo-doped Ru crystal nanocluster structure, wherein RuMo atomic clusters are uniformly distributed on a two-dimensional carbon substrate, providing a large number of catalytically active centers; having excellent HER function, capable of inhibiting the poisoning effect of OH radicals during alkaline electrolysis of water; and a one-pot gradient pyrolysis method that does not require tedious steps such as dissolution, mixing, drying, and washing. The preparation method is economical, efficient, simple, and easy to implement, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to a preparation method of a Mo-doped Ru cluster hydrogen evolution catalyst capable of inhibiting OH radical poisoning, and belongs to the field of electrocatalytic materials. Background Art

[0002] Hydrogen (H2) has the characteristics of high calorific value (143kJ / g) and zero carbon emissions from combustion products, and is considered an ideal green and clean energy source. Alkaline water electrolysis is a relatively mature and low-cost large-scale hydrogen production method. However, the cathode hydrogen evolution reaction (HER) in water electrolysis is highly dependent on platinum (Pt)-based materials. The use of Pt faces cost and resource scarcity issues, as well as stability issues in non-acidic systems, which limits the further promotion and application of water electrolysis technology. Therefore, the search for catalysts with high activity, long life and relatively low price has become a hot topic of current research.

[0003] The price of the semi-noble metal ruthenium (Ru) is only 1 / 3 of that of Pt, and it has a suitable Ru-H binding energy (~67 kcal mol -1 Ru has high water splitting ability and can provide hydrogen protons (H2O+e - →H ad +OH - ), and is therefore widely used in the field of alkaline hydrogen production. However, the strong adsorption ability of Ru for OH* leads to the poisoning effect of the Ru surface of the active site. Therefore, optimizing the adsorption and desorption ability of Ru for OH* is beneficial to the improvement of the performance of Ru-based alkaline HER. Zhang reported the use of oxygen-philic species SnO2 to optimize the strong adsorption effect of Ru on -OH through the competitive adsorption of SnO2 on -OH (ZHANG, Jiachen, et al. Angew. Chem., Int. Ed. 2022, 134.39: e202209486). Even so, the Ru content in the publicly reported Ru-based hydrogen evolution catalysts is still at least higher than 1wt%.

[0004] Therefore, it is urgent to develop a new type of atomic-level efficient Ru-based catalyst that can achieve high Ru atomic utilization while reducing the amount of Ru metal used and effectively inhibit the poisoning effect of OH on Ru. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a Mo-doped Ru cluster hydrogen evolution catalyst capable of inhibiting OH radical poisoning.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] Provided is a method for preparing a Mo-doped Ru cluster hydrogen evolution catalyst capable of inhibiting OH radical poisoning, comprising the following steps:

[0008] (1) Weigh a nitrogen source, a carbon source, a precursor of metallic molybdenum, and a precursor of metallic ruthenium in a mass ratio of 1600:40:1:1; mix them evenly, place them in a tube furnace, and introduce inert gas;

[0009] (2) Maintaining an inert atmosphere, the temperature was raised from room temperature, and continuous heat treatment was performed according to a gradient of 207°C for 2 h, 550°C for 6 h, and 900°C for 3 h; after naturally cooling to room temperature, a black powdery solid, i.e., a Mo-doped Ru cluster hydrogen evolution catalyst, was obtained.

[0010] As a preferred embodiment of the present invention, the carbon source is glucose.

[0011] As a preferred embodiment of the present invention, the nitrogen source is melamine.

[0012] As a preferred embodiment of the present invention, the precursor of the metallic molybdenum is anhydrous molybdenum chloride.

[0013] As a preferred embodiment of the present invention, the precursor of the metallic ruthenium is anhydrous ruthenium chloride.

[0014] As a preferred embodiment of the present invention, the inert gas is argon.

[0015] As a preferred embodiment of the present invention, during the continuous heat treatment process, the temperature is increased at a rate of 5°C / min.

[0016] The present invention further provides a method for using the catalyst prepared by the above method in an electrochemical hydrogen evolution reaction, wherein the catalyst is used for the hydrogen evolution reaction (HER) at the cathode in the electrolysis of water.

[0017] Description of the invention principle:

[0018] This invention utilizes a one-pot gradient temperature pyrolysis method to prepare amorphous RuMo clusters, a unique atomic-scale hydrogen evolution electrocatalyst. By uniformly dispersing Mo-doped Ru nanoclusters on a two-dimensional carbon material, the Ru coordination structure is modified, optimizing the electronic structure of the catalytically active sites and thus the adsorption energy barrier for OH. Furthermore, the atomically dispersed catalyst provides a large number of active sites, achieving efficient atomic utilization.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention provides a bimetallic atomic-level hydrogen evolution catalyst having a Mo-doped Ru crystal nanocluster structure. The RuMo atomic clusters are evenly distributed on a two-dimensional carbon substrate, providing a large number of catalytically active centers.

[0021] 2. The catalyst of the present invention has excellent HER performance. The doping of Mo atoms in the Ru cluster optimizes the electronic structure of Ru and the adsorption energy of Ru on -OH, which can inhibit the poisoning effect of -OH during the alkaline electrolysis of water.

[0022] 3. The present invention adopts a one-pot gradient pyrolysis method, which does not require tedious steps such as dissolution, mixing, drying, and washing. The preparation method is economical, efficient, simple and easy.

[0023] 4. The catalyst preparation method of the present invention uses a small amount of metal precursor, and the precursor raw materials used are abundant in reserves and low in cost. The addition of Mo further reduces the use of the semi-precious metal Ru, and the product contains only 0.4wt% Ru, which is much lower than existing similar catalyst products. Therefore, it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 TEM image of RuMo / NC in the present invention;

[0025] Figure 2 is the STEM image of RuMo / NC in the present invention;

[0026] Figure 3 is the X-ray absorption spectrum of RuMo / NC in the present invention;

[0027] Figure 4 is the double layer capacitance diagram of RuMo / NC in 1 M KOH in the present invention;

[0028] Figure 5 The RuMo / NC in the present invention has a very high atomic utilization rate compared with other reported Ru-based hydrogen evolution catalysts;

[0029] Figure 6 is the adsorption free energy of H* and OH* on RuMo / NC in the present invention.

[0030] Figure 7 is the adsorption free energy of H* and OH* on Ru / NC in Comparative Example 1. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0032] Melamine, glucose, anhydrous platinum chloride, and anhydrous ruthenium chloride used in the following examples were all purchased from Sigma-Aldrich Co., Ltd. and were of analytical grade.

[0033] Example 1

[0034] The preparation of Mo-doped Ru cluster hydrogen evolution catalyst comprises the following steps:

[0035] (1) Weigh 8 g of dicyandiamide (DADC), 200 mg of glucose (GC), 5 mg of anhydrous molybdenum chloride (MoCl5), and 5 mg of anhydrous ruthenium chloride (RuCl3), place them in a quartz boat and mix them evenly; then place them in a tube furnace and continuously flow argon.

[0036] (2) Maintaining an inert atmosphere, the temperature was raised from room temperature to perform a gradient temperature heat treatment: first, the temperature was raised to 207°C at a rate of 5°C / min and held for 2 hours to allow the melamine to be fully mixed with the other reactants in a molten state; then, the temperature was raised from 207°C to 550°C and held for 6 hours to allow the carbon source and nitrogen source to condense to form a carbon trinitrogen tetrakis (C3N4) structure; and then the temperature was raised from 550°C to 900°C and held for 3 hours to allow some nitrogen atoms to detach from the carbon layer and form an amorphous RuMo cluster structure, which was uniformly distributed on the two-dimensional carbon substrate. After the heat treatment was completed, the catalyst was naturally cooled to room temperature to obtain a black powder solid, namely, a Mo-doped Ru cluster hydrogen evolution catalyst, denoted as RuMo / NC.

[0037] The prepared RuMo / NC catalyst was observed by dark field scanning transmission electron microscopy (STEM) to observe its micromorphology. Figure 1-2 As shown. Figure 1 It can be seen that atomic-scale nanoclusters of RuMo with a diameter of 1 nm are uniformly dispersed on the two-dimensional carbon layer; Figure 2 It can be seen that the clusters have no obvious crystal stripes and appear to be amorphous.

[0038] Examples of how catalysts can be used:

[0039] (1) 1 mL of Nafion was added to 1 mL of isopropanol and 48 mL of deionized water, and ultrasonicated for 5 min to prepare 50 mL of 1 wt‰ Nafion solution (mass concentration);

[0040] (2) 2 mg of powdered catalyst RuMo / NC was added to 1 mL of 1 wt‰ Nafion solution and ultrasonicated for 2 h to obtain a uniformly dispersed 2 mg / mL catalyst slurry;

[0041] (3) Cut a 1.5 cm × 1 cm hydrophobic carbon paper, take 100 μL of catalyst slurry and evenly drop it on the hydrophobic carbon paper 1 cm 2 The surface of the carbon paper electrode was dried naturally to obtain the RuMo / NC catalyst coating amount of 0.2 mg / cm 2 ;

[0042] (4) Referring to the above steps, carbon paper electrodes coated with Ru / NC catalyst and Mo / NC catalyst were prepared respectively;

[0043] (5) A three-electrode system was constructed in a single electrolyzer: a carbon paper electrode was used as the working electrode for hydrogen evolution reaction (HER), a platinum sheet was used as the counter electrode, a saturated Hg / HgO electrode was used as the reference electrode, and the electrolyte was 1.0 M KOH.

[0044] Comparative Example 1

[0045] This comparative example basically refers to the operating steps of Example 1, except that in step (1), only 5 mg of anhydrous ruthenium chloride (RuCl3) is added as the metal precursor, and no Mo precursor is added. The ruthenium catalyst finally obtained is recorded as Ru / NC.

[0046] The catalysts of Example 1 and Comparative Example 1 were subjected to X-ray absorption fine structure spectroscopy analysis to further obtain the atomic coordination of Ru. The results are as follows: Figure 3 As shown in the figure, the Ru 3p spectrum of RuMo / NC exhibits a double peak attributed to Ru 3p3 / 2 and Ru 3p1 / 2; this result further indicates that, under high-temperature reduction, Ru exists in the catalyst in a metallic state. Compared to Ru / NC, the Ru 3p peak in RuMo / NC shifts negatively by 0.7 eV, indicating that the introduction of Mo transfers electrons from Mo to Ru atoms, optimizing the electronic structure of Ru atoms.

[0047] Comparative Example 2

[0048] This comparative example basically refers to the operating steps of Example 1, except that in step (1), only 5 mg of anhydrous molybdenum chloride (MoCl5) is added to the metal precursor, and no Ru precursor is added. The molybdenum catalyst finally obtained is recorded as Mo / NC.

[0049] Comparative experiment and result analysis:

[0050] 1. Linear sweep voltammetry (LSV) test

[0051] The catalysts prepared in Example 1 and Comparative Examples 1-2 were subjected to cyclic voltammetry (CV) tests. After activation, the switching program was a linear sweep program (LSV), the test interval was 0 to -0.8 V vs. RHE, the sweep rate was 10 mV / s, and the overpotential was 0 mA cm relative to the reversible hydrogen electrode (RHE). -2 With 10mA cm -2 The RuMo / NC catalyst with both Ru and Mo elements introduced has a lower potential of 10 mA cm compared to the Ru / NC catalyst with only Ru and the Mo / NC catalyst with only Mo introduced. -2 The potential of RuMo / NC at 10 mA cm -2 The overpotential is 25 mV, and the catalyst performance is better than commercial 10% Pt / C.

[0052] In order to further explore the activity of the catalyst, cyclic voltammetry (CV) was used to measure the double layer capacitance (C dl ) was calculated, and the active areas of the catalysts of Example 1, Comparative Example 1, and Comparative Example 2 were estimated: CV curves of different catalysts were obtained at different scan rates (20-100 mV / s) in the non-Faraday range (0.1 V to 0.2 V vs. RHE), and the anode-cathode current density difference (Δj = j 阳极 -j 阴极 ) is linearly fitted with the scanning speed, and the slope of the fitting is 2 times the double electric layer. Figure 4 As shown in Figure 3, RuMo / NC has the largest slope, indicating that RuMo / NC has the largest active area and has more active sites than Ru / NC and Mo / NC.

[0053] 2. Comparison with existing recorded catalysts

[0054] The hydrogen evolution performance of the RuMo / NC catalyst in the present invention is compared with the Ru-based catalysts reported so far ( Figure 5 ), containing only 0.4 wt% loading, which is lower than the publicly reported catalyst loading. At the same time, the catalyst can achieve efficient alkaline hydrogen evolution performance, demonstrating the high atomic utilization rate and efficient catalytic performance of the catalyst.

[0055] By DFT calculation, such as Figure 6 、 7 As shown in the figure, compared with Ru / NC catalyst, RuMo / NC can achieve better hydrogen evolution performance by introducing Mo. In addition, the adsorption free energy of OH radicals in the RuMo / NC system is much smaller than that of Ru / NC, indicating that the doping of Mo optimizes the electronic structure of Ru, thereby suppressing the poisoning effect of OH radicals on Ru groups.

[0056] 3. Hydrogen evolution performance test:

[0057] (1) Referring to the steps in the application example of Example 1, carbon paper electrodes coated with Ru / NC catalyst and Mo / NC catalyst were prepared respectively;

[0058] (2) Referring to the application example of Example 1, two carbon paper electrodes were used as working electrodes to build a three-electrode system in a single electrolytic cell.

[0059] (3) The hydrogen evolution performance test was conducted on the three-electrode system constructed using the three catalysts. In the test, the Hg / HgO electrode was converted into a reversible hydrogen electrode (RHE). The conversion relationship is: E RHE =E Hg / HgO+0.098+0.0591pH, pH = 14. RuMo / NC at 10mA / cm 2 The overpotential is 25 mV, which is much smaller than the comparative samples Ru / NC (47.6 mV) and Mo / NC (328.0 mV), and better than the commercial catalyst Pt / C (109.5 mV).

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a Mo-doped Ru cluster hydrogen evolution catalyst that inhibits OH radical poisoning, characterized in that: The following steps are involved: (1) Weigh a nitrogen source, a carbon source, anhydrous molybdenum chloride precursor, and anhydrous ruthenium chloride precursor in a mass ratio of 1600:40:1:1; mix them evenly and place them in a tube furnace, and introduce inert gas; the carbon source is glucose, and the nitrogen source is melamine; (2) Maintaining an inert atmosphere, the temperature was raised from room temperature, and continuous heat treatment was performed according to a gradient of 207°C for 2 h, 550°C for 6 h, and 900°C for 3 h. After naturally cooling to room temperature, a black powder solid, namely a Mo-doped Ru cluster hydrogen evolution catalyst, was obtained. The catalyst has a Mo-doped Ru crystal nanocluster structure and is uniformly dispersed on a two-dimensional carbon substrate as a catalytic active center.

2. The method according to claim 1, characterized in that The inert gas is argon.

3. The method according to claim 1, characterized in that During the continuous heat treatment, the temperature is increased at a rate of 5°C / min.

4. Use of the catalyst prepared by the method according to claim 1 in electrochemical hydrogen evolution reaction, characterized in that: The catalyst is used for the hydrogen evolution reaction at the cathode in the electrolysis of water.

Images