Seven-core tungsten-vanadium heteropolyacid alkoxy derivative as well as preparation method and application thereof

Abstract

The invention provides a seven-core tungsten-vanadium heteropolyacid alkoxy derivative and a preparation method and application thereof, and belongs to the organic and inorganic hybrid material technology, the chemical formula of the seven-core tungsten-vanadium heteropolyacid alkoxy derivative is (C16H36N) 2 [WV6O16 {(OCH2) 3CCH2OH} 2], the seven-core tungsten-vanadium heteropolyacid alkoxy derivative is composed of a metal-oxygen cluster anion [WV6O16 {(OCH2) 3CCH2OH} 2] 2-and two tetrabutylammonium cations, the preparation method comprises the following steps: dissolving polytungstate, polyvanadate and a trihydroxymethyl compound in an anhydrous organic solvent according to a ratio, and carrying out microwave-assisted synthesis. According to the preparation method, the Tris functionalized heptanuclear tungsten-vanadium heteropolyacid with the metal tungsten-vanadium ratio of 1: 6 is prepared through a simple microwave-assisted synthesis method, the structural diversity of a tungsten-vanadium heteropolyacid system is enriched, and the synthesized heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative has excellent oxidation-reduction capacity and has extremely high application value in the field of electro-catalytic hydrogen evolution.

Description

Technical Field

[0001] The present invention relates to the technical field of organic-inorganic hybrid materials, and particularly relates to a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative, a preparation method thereof, and an application thereof. Background Art

[0002] Polyoxometalates (POMs) are a class of ionic metal-oxygen clusters formed by the polycondensation of oxyacids of early transition metal ions (such as Mo(VI), W(VI), V(V), Nb(V), Ta(V), etc.). The compositions and structures of POMs are diverse and can be divided into two categories, including isopoly metalates (such as {Mo6O 19} and {V 10 O 28}) and heteropoly metalates (such as {SiW 12 O 40} and {MnMo6O 24}). Through different types of connections (such as coplanar, corner-sharing, and edge-sharing connections) between metal-oxygen coordination blocks, POMs can form a variety of classical structures (such as Keggin type, Lindqvist type, and Anderson type) and various interesting topological structures (such as ring-shaped, spherical, and wheel-shaped). Benefiting from the inherent properties of POMs (including multi-metal centers, redox reversibility, strong Brønsted acidity, etc.), POM clusters have a wide range of applications in the fields of catalysis, biochemistry, and energy storage and conversion.

[0003] Tungsten-vanadium heteropolyacids are a class of inorganic compounds with unique structures and functions, and have attracted much attention due to their excellent catalytic performance and redox properties. The synergistic effect between tungsten and vanadium elements enables them to form multinuclear cluster compounds with unique structures, showing higher activity and selectivity than traditional materials in a variety of catalytic reactions. Therefore, such compounds have broad and important application prospects in the fields of chemical synthesis, environmental governance, and energy conversion. Currently, it is found that the structural types of tungsten-vanadium heteropolyacids are mainly represented by Lindqvist type and Dawson type. Compounds of these two structural types have been widely applied in multiple directions such as catalytic oxidation reactions, fuel desulfurization, proton exchange membranes, lithium-ion battery electrode materials, and anti-tumor drugs. However, most known tungsten-vanadium heteropolyacids have high symmetry, which greatly limits the construction of chiral molecules of polyacid derivatives and severely restricts the application of such compounds in the fields of asymmetric catalysis, biology, etc. To break through this dilemma, designing tungsten-vanadium heteropolyacids with asymmetric structures not only is expected to overcome the problem of chiral molecule construction but also will open up broad prospects for their synthesis and multi-field applications. Summary of the Invention

[0004] In view of the technical problems existing in the background art, the present invention provides a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative, its preparation method and application, aiming to solve the technical problem that the high symmetry of existing tungsten-vanadium heteropolyacid compounds limits the construction and application of chiral molecules of polyacid derivatives.

[0005] First, the present invention provides a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative with the chemical formula (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2], which is composed of a metal-oxygen cluster anion [WV6O 16 {(OCH2)3CCH2OH}2] 2- and two tetrabutylammonium cations.

[0006] Preferably, (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2] belongs to the monoclinic system, the space group is C2 / c, and the unit cell parameters are: a = 24.394(3) Å, b = 32.599(4) Å, c = 16.883(2) Å and α = 90°, β = 101.312(3)°, γ = 90°, Z = 8.

[0007] Preferably, [WV6O 16 {(OCH2)3CCH2OH}2] 2- is connected by a heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster and two Tris-OH. The heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster is composed of an octahedron formed by W-O bonds and six octahedrons formed by V-O bonds. Among them, the tungsten atom forms a pentahedron structure by connecting with four vanadium atoms; Among them, one Tris-OH is connected to the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster at the intersection of the vertices of three octahedrons where three vanadium atoms of the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster are connected to oxygen, and the other Tris-OH is connected to the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster through three vertices of an octahedron where one vanadium atom is connected to oxygen.

[0008] Second, the present invention provides a preparation method of a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative, including the following steps: Dissolve polytungstate, polyvanadate and trimethylol compounds in a water-free organic solvent, carry out microwave hydrothermal reaction, filter and collect the filtrate; mix the filtrate with ether, stir to obtain a solid, dissolve the solid in its good solvent, and then diffuse it with its poor solvent in a closed environment. Through the gas-phase diffusion method, a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative is obtained.

[0009] Preferably, the polytungstate is decatungstate (C 16 H 36 N)4[W 10 O 32 , the polyvanadate is decavanadate (C 16 H 36 N)3[H3V 10 O 28 , and the trihydroxymethyl compound is pentaerythritol; the molar ratio of decatungstate, decavanadate and pentaerythritol is about 1:1:(3-4).

[0010] Preferably, the molar ratio of decatungstate, decavanadate and pentaerythritol is about 1:1:3.3.

[0011] Preferably, the poor solvent includes diethyl ether and the good solvent includes methanol.

[0012] Preferably, the conditions of the microwave hydrothermal reaction are as follows: the reaction temperature is 110-130 °C, the reaction time is 10-30 min, the heating-up time is 10-20 min, and the upper limit of the microwave power is 1000 W.

[0013] Preferably, the heating-up time is 10-15 min; the product yield is relatively high at this heating rate.

[0014] Preferably, the heating-up time is 10 min; the product yield reaches the highest at this heating rate.

[0015] Preferably, the reaction temperature is 110-120 °C; the product yield is relatively high within this temperature range.

[0016] Preferably, the reaction temperature is 120 °C; the product yield reaches the highest when reacting at this temperature.

[0017] In a third aspect, the present invention provides an application of a heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative in the preparation of an electrocatalytic hydrogen evolution material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: Through a simple microwave reaction, the present invention synthesizes a novel heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative, and obtains a Tris-functionalized heptanuclear tungsten-vanadium heteropolyacid with a metal tungsten-vanadium ratio of 1:6, enriching the structural diversity of the tungsten-vanadium heteropolyacid system. The synthesized heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative has excellent redox ability and has extremely high application value in the field of electrocatalytic hydrogen evolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the synthesis process of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative in the embodiment of the present invention; Figure 2Structural diagram of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative in the embodiments of the present invention; Figure 3 Structural diagram of the trihydroxymethyl compound used in the embodiments of the present invention; Figure 4 is the XPS spectrum of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative prepared in the embodiments of the present invention. Among them, (a) is the XPS wide spectrum of the tungsten-vanadium heteropolyacid alkoxy derivative, (b) is the XPS narrow spectrum of vanadium element, and (c) is the XPS narrow spectrum of tungsten element; Figure 5 Cyclic voltammogram of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative in the embodiments of the present invention; Figure 6 Overpotential diagram of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative and carbon cloth in the embodiments of the present invention; Figure 7 i-t diagram of the heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative in the embodiments of the present invention. Detailed implementation manners

[0020] The embodiments of the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0021] For those not specified in the embodiments, the technical conditions described in the literature in the field or the product specifications are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase or commonly used in the field.

[0022] Term definition: The Tris ligand refers to a trihydroxymethyl compound (RH2C-C(CH2OH)3) (R is different organic groups); Tris-OH refers to when R = OH, Tris-OH is pentaerythritol.

[0023] In the following embodiments of the present invention, the preparation method of the decavanadate (C 16 H 36 N)3[H3V 10 O 28 used in the experiment: Weigh 10 g of sodium metavanadate and dissolve it in 100 mL of water. After rapid stirring until completely dissolved, add 1 mol / L dilute hydrochloric acid dropwise to the solution to adjust the pH to 2-3, and stir for 5 hours to obtain a sodium metavanadate solution; Weigh 26 g of tetrabutylammonium bromide and dissolve it in 100 mL of water to obtain a tetrabutylammonium bromide solution; Under stirring, slowly add the sodium metavanadate solution to the tetrabutylammonium bromide solution, stir for 12 h, filter the product by suction, and air-dry it for one week to obtain a yellow powder solid, which is the target product (C 16 H36 N)3[H3V 10 O 28 , with a yield of 80% (calculated based on V).

[0024] In the following examples of the present invention, the decatungstate (C 16 H 36 N)4[W 10 O 32 used in the experiment was prepared as follows: Weigh 16 g of sodium tungstate dihydrate and dissolve it in 100 mL of hot water. After quickly stirring until completely dissolved, add 100.5 mmol of boiling dilute hydrochloric acid to the solution, and quickly stir for 1 - 2 min, then stir for 5 h to obtain an aqueous solution of sodium tungstate. Weigh 15.6 g of tetrabutylammonium bromide and dissolve it in 25 mL of water to obtain a tetrabutylammonium bromide solution. While stirring, slowly drop the sodium tungstate solution into the tetrabutylammonium bromide solution and stir for 12 h. Then filter the product by suction. During the suction filtration process, wash it 3 times with 40 mL of hot water, 2 times with 60 mL of ethanol, and 2 times with 100 mL of ether. After air-drying for one week, a white powder solid is obtained, which is the target product (C 16 H 36 N)4[W 10 O 32 , with a yield of 75% (calculated based on W).

[0025] I. Preparation method Example 1 Synthesis of heptanuclear tungsten - vanadium heteropolyacid alkoxy derivative (C 16 H 36 N)2[WV6O 16 {(OCH2)3C CH2OH}2] The schematic diagram of the synthesis process of the heptanuclear tungsten - vanadium heteropolyacid alkoxy derivative described in this example is as shown in Figure 1 and the specific operation steps of the synthesis process are as follows: S1. Weigh 312 mg (0.189 mmol) of decavanadate (C 16 H 36 N)3[H3V 10 O 28 , 627 mg (0.189 mmol) of decatungstate (C 16 H 36 N)4[W 10 O 32 , and 84 mg (0.615 mmol) of pentaerythritol (the structure is as shown in Figure 3 ), and dissolve them in 10 mL of N,N - dimethylacetamide (DMAc) (pre - dehydrated with CaH2); S2. After stirring until completely dissolved, pour the solution into a 100 mL microwave - specific polytetrafluoroethylene reaction kettle, seal the reaction kettle tightly, set the temperature - rising time to 10 min, the reaction temperature to 120 °C, the reaction time to 20 min, and the upper limit of microwave power to 1000 W, and carry out microwave reaction; S3. Filter the resulting reddish - brown solution into 60 mL of diethyl ether, stir to obtain a brown solid, filter and then air - dry naturally, and the yield is 28% (calculated by volume); S4. Use diethyl ether as the poor solvent and methanol as the good solvent for vapor diffusion to obtain orange - block crystals. The crystals are washed with 20 mL of deionized water and 20 mL of absolute ethanol and then air - dried naturally.

[0026] Test Example (1) The crystal structure of the compound prepared in Example 1 was determined and characterized by X - ray single - crystal diffraction technology. The unit - cell parameters are as follows: a = 24.394(3) Å, b = 32.599(4) Å, c = 16.883(2) Å, α = 90°, β = 101.312(3)°, γ = 90°, Z = 8, belonging to the monoclinic system, and the space group is C2 / c.

[0027] (2) The compound prepared in Example 1 was detected by XPS. The results are shown in Figure 4. The two peaks located at 34.12 eV and 516.20 eV belong to V 5+ and W 6+ , indicating that all vanadium and tungsten atoms in (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2] maintain the 5 + and 6 + valence states.

[0028] Through single - crystal X - ray diffraction and XPS detection, it is confirmed that the obtained product is the compound shown in Figure 2 . (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2] compound consists of a metal - oxygen cluster anion [WV6O 16 {(OCH2)3CCH2OH}2] 2- and two tetrabutylammonium cations (C4H9)4N +Composition. Its anionic part is composed of a heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster connected by two Tris-OH. The polyacid anionic cluster consists of an octahedron formed by W-O bonds and six octahedrons formed by V-O bonds. Among them, the tungsten atom forms a pentahedron structure by connecting with four vanadium atoms. One Tris-OH is connected to the polyacid cluster at the intersection of the vertices of three octahedrons where three vanadium atoms of the polyacid cluster are connected to oxygen, and the other Tris-OH is connected to the polyacid cluster through three vertices of an octahedron where one vanadium atom is connected to oxygen.

[0029] (3) Electrochemical performance tests were carried out on the alkoxyl derivatives of the heptanuclear tungsten-vanadium heteropolyacid prepared in Example 1. The test method is as follows: The electrochemical properties of the compound were tested by an electrochemical workstation with a three-electrode system. The reference electrode is an Ag / AgCl electrode, the working electrode is a glassy carbon electrode, and the platinum column electrode is the auxiliary electrode. C 16 H 36 NPF6 solution was used as the supporting electrolyte with a concentration of 0.1 mol / L, and acetonitrile was used as the solvent. The sample concentration was 0.1 mmol / L. Before the test, the electrode was polished for at least 30 min. Argon was passed for 30 min before testing the blank, and argon was passed for 15 min before testing the sample. The gas should be turned off during the test. The scanning voltage range was set as: -1.5~1.5 V, and the scanning speed was set as: 25 mV / s.

[0030] The test results are as Figure 5 shown. There are 5 redox peaks in the figure. Among them, the position of 0.744 V is an irreversible oxidation peak, there is a pair of reversible redox peaks with a half-wave potential of -0.293 V, and there is a pair of quasi-reversible redox peaks with a half-wave potential of -0.795 V. There are 5 redox processes in the range of -1.5 V~0 V, indicating that the substance has excellent redox ability.

[0031] (4) Electrochemical hydrogen evolution tests were carried out on the alkoxyl derivatives of the heptanuclear tungsten-vanadium heteropolyacid prepared in Example 1. The specific detection method is as follows: 7.0 mg of the sample and 100 µL of Nafion solution were dispersed in 250 µL of absolute ethanol by ultrasonic treatment for 1 hour to form a uniform ink. 300 µL of the ink was coated on the activated (Activation: Cut the commercially purchased carbon cloth into 3×2 cm 2 size, activate it with a mixed solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 1:1) at 80 °C for 30 min, and wash it with deionized water and ethanol and then dry) carbon cloth (1×2 cm 2), and dried at room temperature. All electrochemical tests were carried out using a standard three - electrode system on a CHI760E electrochemical analyzer (CH Instruments, Shanghai). All potentials in this article were referenced to the reversible hydrogen electrode (RHE), and the calculation formula was E(RHE) = E(Hg / HgO) + 0.098 + 0.059*pH. Linear sweep voltammetry (LSV) was carried out in 1 M KOH, using a Hg / HgO electrode as the reference electrode, a graphite rod as the counter electrode, and a carbon cloth as the working electrode. Chronoamperometry (i - t) was carried out in 1 M KOH, using a Hg / HgO electrode as the reference electrode, a graphite rod as the counter electrode, and a carbon cloth as the working electrode. The hydrogen evolution test was carried out at a constant voltage of 1.3 V for up to 12 h. Figure 6 is the over - potential diagram of the heptanuclear tungsten - vanadium heteropolyacid alkoxy derivative and the carbon cloth. Figure 7 is the i - t diagram of the heptanuclear tungsten - vanadium heteropolyacid alkoxy derivative, as Figure 6 and Figure 7 shown. The hydrogen evolution over - potential was measured to be 502 mV at 10 mA cm -2 (624 mV for pure carbon cloth). After 12 h of i - t testing, the current density only changed by 3 mA cm -2 , indicating that this substance has the potential to be an excellent electrocatalytic hydrogen evolution material.

[0032] Example 2 The difference between this example and Example 1 is that the heating - up time in step S2 is 15 min, and the rest of the steps are the same as those in Example 1. The yield of the target product is 20% (calculated by V).

[0033] Example 3 The difference between this example and Example 1 is that the heating - up time in step S2 is 20 min, and the rest of the steps are the same as those in Example 1. The yield of the target product is 18% (calculated by V).

[0034] Example 4 The difference between this example and Example 1 is that the reaction temperature in step S2 is 110 °C, and the rest of the steps are the same as those in Example 1. The yield of the target product is 10% (calculated by V).

[0035] Example 5 The difference between this example and Example 1 is that the reaction temperature in step S2 is 130 °C, and the rest of the steps are the same as those in Example 1. The yield of the target product is 15% (calculated by V).

[0036] Comparative Example 1 The target compound was prepared by the traditional solution method: Weighed 312 mg (0.189 mmol) of decavanadate (C16 H 36 N)3[H3V 10 O 28 , 627 mg (0.189 mmol) decavanadate (C 16 H 36 N)4[W 10 O 32 , 84 mg (0.615 mmol) pentaerythritol (structure as Figure 3 shown), dissolved in 10 mL of N,N-dimethylacetamide (DMAc) (previously dehydrated with CaH2); after stirring until completely dissolved, the solution was poured into a 50 mL round-bottom flask, and a reflux condenser was set up. The solution was heated in an oil bath at 110, 120, and 130 °C for 12 h, 24 h, and 36 h respectively. After detection, the yields of the target compound in the three experiments were all 0%, and the target compound was not obtained by the traditional solution method.

[0037] Comparative Example 2 The target compound was prepared by hydrothermal synthesis: Weighed 312 mg (0.189 mmol) of decavanadate (C 16 H 36 N)3[H3V 10 O 28 , 627 mg (0.189 mmol) of decatungstate (C 16 H 36 N)4[W 10 O 32 , 84 mg (0.615 mmol) of pentaerythritol (structure as Figure 3 shown), dissolved in 10 mL of N,N-dimethylacetamide (DMAc) (previously dehydrated with CaH2); after stirring until completely dissolved, the solution was poured into the inner liner of a 50 mL high-pressure reactor, and the reactor was sealed and placed in an oven. The reaction was carried out at 110, 120, and 130 °C for 12 h, 24 h, and 36 h respectively. After detection, the yields of the target compound in the three experiments were all 0%, and the target compound was not obtained by hydrothermal synthesis.

[0038] It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and the same effect as the technical idea within the technical scope of the present invention are all included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some constituent elements of the embodiments are also included in the scope of the present invention.

Claims

1. A heptanuclear tungsten-vanadium heteropoly acid alkoxy derivative, characterized in that, Its chemical formula is (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2], which consists of a metal-oxygen cluster anion [WV6O 16 {(OCH2)3CCH2OH}2] 2- and two tetrabutylammonium cations.

2. A heptanuclear tungsten-vanadium heteropolyacid alkoxy derivative according to claim 1, characterized in that, The (C 16 H 36 N)2[WV6O 16 {(OCH2)3CCH2OH}2] belongs to the monoclinic system, with the space group C2 / c. The unit cell parameters are: a = 24.394(3) Å, b = 32.599(4) Å, c = 16.883(2) Å, α = 90°, β = 101.312(3)°, γ = 90°, and Z = 8.

3. A heptanuclear tungsten vanadium heteropoly acid alkoxy derivative according to claim 1, characterized in that The described [WV6O 16 {(OCH2)3CCH2OH}2] 2- is composed of a heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster and two Tris-OH linkages; The heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster is composed of an octahedron formed by W-O bonds and six octahedrons formed by V-O bonds. Among them, the tungsten atom forms a pentahedron structure by connecting with four vanadium atoms. Among them, one Tris-OH is connected to the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster at the junction of the vertices of three octahedrons where three vanadium atoms of the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster are connected to oxygen, and the other Tris-OH is connected to the heptanuclear tungsten-vanadium heteropolyacid {WV6} cluster through three vertices of an octahedron where one vanadium atom is connected to oxygen.

4. The preparation method of the heptanuclear tungsten vanadium heteropoly acid alkoxy derivative according to any one of claims 1 to 3, characterized in that, It includes the following steps: Dissolve the polytungstate, polyvanadate and trimethylol compound in an organic solvent other than water, carry out microwave-assisted synthesis, filter and collect the filtrate; mix the filtrate with ether, stir, precipitate a solid, dissolve the solid in its good solvent, and then diffuse it with its poor solvent in a closed environment to obtain the alkoxy derivative of the heptanuclear tungsten-vanadium heteropolyacid.

5. The preparation method of the heptanuclear tungsten vanadium heteropoly acid alkoxy derivative according to claim 4, characterized in that, The polytungstate is decatungstate, the polyvanadate is decavanadate, and the trimethylol compound is pentaerythritol; the molar ratio of the decatungstate, decavanadate and pentaerythritol is about 1:1:(3-4).

6. The preparation method of the heptanuclear tungsten vanadium heteropolyacid alkoxy derivative according to claim 5, characterized in that, The molar ratio of the decatungstate, decavanadate and pentaerythritol is about 1:1:3.

3.

7. The preparation method of the heptanuclear tungsten vanadium heteropolyacid alkoxy derivative according to claim 4, characterized in that, The poor solvent includes ether, and the good solvent includes methanol.

8. The preparation method of the heptanuclear tungsten vanadium heteropoly acid alkoxy derivative according to claim 4, characterized in that, The conditions of the microwave-assisted synthesis are as follows: the reaction temperature is 110-130 °C, the reaction time is 10-30 min, the heating-up time is 10-20 min, and the upper limit of the microwave power is 1000 W.

9. The preparation method of the heptanuclear tungsten-vanadium heteropoly acid alkoxy derivative according to claim 8, characterized in that, The heating-up time is 10 min; the reaction temperature is 120 °C.

10. Use of the alkoxy derivative of the heptanuclear tungsten-vanadium heteropolyacid according to any one of claims 1-3 in the preparation of an electrocatalytic hydrogen evolution material.

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