CN112108146A

CN112108146A - Phase-transition ruthenium oxide, preparation method thereof and application thereof in seawater electrolysis hydrogen production

Info

Publication number: CN112108146A
Application number: CN202011048677.4A
Authority: CN
Inventors: 阳晓宇; 方芳; 王永; 沈乐伟; 余豪争; 刘钰; 赵小芳; 田歌; 常刚刚
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2020-12-22
Anticipated expiration: 2040-09-29
Also published as: CN112108146B

Abstract

The invention provides a method for preparing phase-transition ruthenium oxide, which is obtained by solvothermal treatment, wherein an X-ray powder diffraction pattern has small-angle shift or new diffraction peaks relative to a plurality of diffraction peaks of an XRD standard pattern of ruthenium dioxide. The invention adopts a solvothermal method which is easy to realize industrially to process the ruthenium dioxide to obtain the ruthenium oxide with phase transition, can greatly improve the water electrolysis performance of the material and the performance of hydrogen production by electrolyzing seawater, and has strong practical significance.

Description

Phase-transition ruthenium oxide, preparation method thereof and application thereof in seawater electrolysis hydrogen production

Technical Field

The invention belongs to the field of inorganic nano catalytic material manufacturing, and particularly relates to an improved method of ruthenium dioxide and application of the improved method in water electrolysis and seawater electrolysis for hydrogen production.

Background

Seawater is liquid water which is most widely distributed and most abundant on the earth, and the green, efficient and sustainable preparation of hydrogen can be realized by electrolyzing seawater to prepare hydrogen, but the pH of the seawater is generally neutral, weak and alkaline, has complex components and contains a plurality of metal cations (such as Na)⁺、K⁺、Ca²⁺And Mg²⁺Etc.) and anions (e.g., Cl)^-、SO₄ ^2-、Br^-And HCO₃ ^-Etc.) so that the electrocatalyst suffers from both poor catalytic activity and poor stability. Noble metal catalysts such as commercial Pt/C and commercial RuO₂Commercial IrO₂The relatively non-noble metal catalyst has better catalytic activity and relatively higher stability in electrolyte with a wide pH range, and is always used as a reference comparative catalyst for evaluating the performance of the electrolyzed water. Ruthenium (Ru) is the least expensive Pt group noble metal, and its chemical valence can vary from-II to + VIII, producing many compounds with unique properties. Wherein, RuO₂Becomes an electric oxygen evolution catalyst which is widely used at present and relates to RuO₂The application of electrocatalytic hydrogen evolution is also reported in early research, and the electrocatalytic hydrogen evolution has better catalytic activity, but the problem of catalytic stability is always existed and is difficult to solve. For RuO₂Improve the catalytic activity and stability of the catalyst, and researchers have conducted many researches and researches on the preparation of RuO with different sizes, shapes, crystallinities and exposed crystal faces₂Other metals are introduced or a multi-metal compound and a multi-metal solid solution are formed by doping, so that the catalytic activity and the stability of the material are regulated and controlled. However, many strategies and methods are complicated and difficult to simultaneously improve the catalytic performance of the material for hydrogen evolution in seawater electrolysis and anodic oxidation reaction, so that the development of a catalyst with high catalytic activity and high stability is the core of the seawater electrolysis fieldProblem to increase RuO₂A simple method of electrolyzing seawater to produce hydrogen remains a challenge.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a post-treatment method of ruthenium dioxide, which can effectively improve the performance of ruthenium dioxide in water electrolysis and seawater electrolysis hydrogen production by changing the integral phase structure of the material through treatment.

In order to achieve the purpose, the invention adopts the technical scheme that:

phase transition ruthenium oxide, wherein the X-ray powder diffraction pattern of the ruthenium oxide has small-angle shift or new diffraction peak generation relative to a plurality of diffraction peaks in the XRD standard pattern of ruthenium dioxide, wherein (110) crystal face corresponding to the peak position shifts 1.5-2 degrees leftwards from 27.5-28.5 degrees, while (101) crystal face corresponding to the diffraction peak disappears at 34.5-35.5 degrees, 3 weaker new peaks are generated between higher angles of 35.4-37.4 degrees, the diffraction peak intensity of (211) crystal face at 53.8-54.8 degrees is not obviously weakened, but the peak width is enlarged, a new diffraction peak is generated at the left shift of 1.5-2.5 degrees, and other diffraction peaks with weaker intensities are also accompanied with similar changes.

The preparation method of the phase-transition ruthenium oxide comprises the following steps:

(1) adding ruthenium dioxide into a solvent, and performing ultrasonic treatment to obtain a black solution; wherein the solvent is an alcohol or an alkali alcohol solution;

(2) standing the solution obtained in the step (1) at a certain temperature and preserving heat for a certain time to obtain the phase-transition ruthenium oxide.

In the scheme, the alkali in the step (1) is one or a mixture of several of alkaline hydroxides such as sodium hydroxide, potassium hydroxide and the like according to any proportion.

In the scheme, the concentration range of the alkali in the alcoholic solution of the alkali is 0-3 mol/L. The alkali can accelerate the phase transition process, and the phase transition can be completed by prolonging the reaction time without adding the alkali.

In the scheme, the dispersion concentration range of the ruthenium dioxide added in the step (2) in the solvent is 0.05-200 mg/mL. The ruthenium dioxide is rutile type ruthenium dioxide, which can be commercially available commercial ruthenium dioxide, or ruthenium dioxide synthesized according to the literature, and has a size of generally 10nm to 10 μm, preferably nano-sized particles, and a size distribution of 50nm to 200 nm.

In the scheme, the alcohol in the step (1) can be one or more of low-carbon organic alcohols such as methanol, ethanol, ethylene glycol, glycerol and the like.

In the scheme, the temperature in the step (2) is 100-200 ℃, and the heat preservation time is 2-48 h.

In the preparation method, the phase transformation of the ruthenium dioxide is caused by the solvent heat treatment, and is reflected in the phase structure that a plurality of diffraction peaks in an X-ray powder diffraction spectrum are subjected to small-angle shift or new diffraction peaks are generated. The ruthenium oxide with phase transition prepared by the method can be applied to water electrolysis and seawater electrolysis hydrogen production as a catalyst.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

firstly, the invention adopts a solvothermal method which is easy to realize industrially to process the ruthenium dioxide particles to obtain the phase-transition ruthenium oxide, and can greatly improve the water electrolysis performance of the material and the performance of hydrogen production by seawater electrolysis. Secondly, the method for post-processing ruthenium dioxide provided by the invention is simple and feasible, stable and safe in reaction, low in cost, capable of large-scale synthesis and suitable for industrial production.

Drawings

FIG. 1(a) is an SEM image of phase-transformed ruthenium oxide obtained after ruthenium dioxide is reacted for 8 hours in ethylene glycol and sodium hydroxide solvothermal at 140 ℃ in example 1 of the present invention, (b) is an SEM image of commercial ruthenium dioxide;

FIG. 2 is an XRD pattern of ruthenium dioxide after solvothermal reaction of ethylene glycol and sodium hydroxide for 8 hours in example 1 of the present invention at 140 ℃;

FIGS. 3(a) and (b) are linear voltammograms of electrogenerated hydrogen and electrogenerated oxygen in 1mol/L KOH electrolyte, respectively, and (c) and (d) are linear voltammograms of electrogenerated hydrogen and current density of 10mA/cm, respectively, for simulated seawater²Stability test of the following. RuO₂-140 is ruthenium dioxide in ethylene glycol and sodium hydroxide solvent as in example 1After the reaction is carried out for 8 hours at the temperature of 140 ℃, phase-transition ruthenium oxide is prepared; by way of comparison, commercial RuO₂Commercial Pt/C is commercial ruthenium dioxide;

FIG. 4 is an SEM image of ruthenium dioxide in example 2 after the reaction for 8 hours at 160 ℃ in the presence of ethylene glycol and sodium hydroxide;

FIG. 5 is an XRD pattern of ruthenium dioxide after solvothermal reaction of ethylene glycol and sodium hydroxide for 8 hours in example 2 of the present invention at 160 ℃;

FIG. 6 is an SEM image of phase-transition ruthenium oxide prepared by reacting ruthenium dioxide in an ethylene glycol solvothermal environment at 140 ℃ for 24 hours in example 3 of the present invention;

FIG. 7 is an XRD pattern of ruthenium dioxide after 24h of solvothermal reaction at 140 ℃ in ethylene glycol according to example 3 of the present invention;

FIG. 8 is an XRD pattern of ruthenium dioxide after reaction for 20h at 160 ℃ in glycerol solvothermal in example 4 of the present invention.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

In the following examples, the starting material ruthenium dioxide used was commercially available ruthenium dioxide, rutile type, with a size distribution mainly between 50nm and 200 nm.

Example 1

A preparation method of phase-transition ruthenium oxide comprises the following steps:

(1) mixing 0.6g of sodium hydroxide with 15mL of ethylene glycol, and dissolving to obtain a colorless transparent solution;

(2) adding 100mg of commercial ruthenium dioxide into the solution in the step (1), and carrying out ultrasonic treatment to obtain a black solution;

(3) placing the solution obtained in the step (2) in an oil bath pan at 140 ℃ and preserving heat for 8 hours; the resulting product was washed with water by centrifugation and the sample was freeze-dried.

The SEM of the phase-transition ruthenium oxide prepared in this example is shown in FIG. 1, and the surface of the phase-transition ruthenium oxide is rougher compared with commercial ruthenium dioxide in the morphology.

The XRD of the phase-transformed ruthenium oxide prepared in this example is shown in fig. 2, which is phase-transformed relative to commercial ruthenium dioxide. As can be seen from FIG. 2, the X-ray powder diffraction pattern of the phase-transition ruthenium oxide obtained in the example is shifted to a small angle relative to the multiple diffraction peaks in the XRD standard pattern of ruthenium dioxide, wherein (110) the corresponding peak position of the crystal face is shifted to the left by 1.5-2 degrees from 27.5-28.5 degrees, while (101) the corresponding diffraction peak at 34.5-35.5 degrees disappears, and 3 relatively weak new peaks are generated between higher angles of 35.4-37.4 degrees, and (211) the diffraction peak at 53.8-54.8 degrees has no obvious intensity but has a wide and large weakened peak width, and a new diffraction peak is generated at 1.5-2.5 degrees, and similar changes are accompanied in the vicinity of other diffraction peaks with weak intensities, which are not listed.

The electrocatalytic performance test of the phase-transition ruthenium oxide prepared in this example is shown in fig. 3, and comprises the following steps:

(1) and preparing the electrocatalyst ink. First, an ink was prepared using 950. mu.l of isopropyl alcohol, 50. mu.l of a 5 wt% Nafion solution, and 5mg of a catalyst. Then, the ink prepared by the catalyst was ultrasonically mixed for 30min, and it was confirmed that the uniformly dispersed catalyst ink was obtained. 10 mu L of the ultrasonically uniform ink is dropped on a rotating disk electrode with the diameter of 5mm in two times of 5 mu L, and naturally dried.

(2) And (5) testing the electrocatalytic hydrogen evolution and oxygen evolution performances. The experiment is carried out on an Autolab electrochemical analyzer, all the electrochemical performance characterization is completed under a three-electrode system, an Ag/AgCl electrode is used as a reference electrode, a carbon rod is used as a counter electrode, and a working electrode is a rotating disk electrode. Respectively neutralizing 1mol/L KOH electrolyte and 1mol/L PBS buffer solution with 3.5 wt% NaCl (pH is actually measured to be 5.8) simulated seawater, and introducing saturated N₂The horizontal coordinate of the linear voltammogram for hydrogen evolution and oxygen evolution tested at a scanning rate of 5mV/s is the voltage of the relative reversible hydrogen electrode (vs. RHE), and the vertical coordinate is the current density.

As can be seen from FIG. 3, in a 1mol/L KOH electrolyte, the phase-converted ruthenium oxide obtained in example 1 (overpotential 28mV @10 mA/cm)²) Exhibits a specific commercial Pt/C (overpotential 61mV @10 mA/cm)²) More excellent hydrogen evolution performance, and has large hydrogen evolution performance and oxygen evolution performance compared with commercial ruthenium oxideAnd (5) lifting the web. In a simulated seawater electrolyte containing 3.5 wt% NaCl in 1mol/L PBS buffer solution, the current density of the electrogenerated hydrogen reaches 10mA/cm²While, RuO₂-140, commercial RuO₂And the overpotentials of commercial Pt/C were 113mV, 194mV and 35mV, respectively, RuO₂140 vs commercial RuO₂The performance is greatly improved, and in a stability test, the performance of commercial Pt/C is compared with RuO₂Fast material decay, comprehensive comparison, RuO₂140 exhibits excellent hydrogen production activity and stability by electrolyzing seawater.

Example 2

(1) mixing 0.6g of sodium hydroxide with 15mL of ethylene glycol, and carrying out ultrasonic treatment until the mixture is dissolved to prepare colorless transparent liquid;

(2) adding 50mg of commercial ruthenium dioxide into the solution in the step (1), and carrying out ultrasonic treatment to obtain a black solution;

(3) putting the solution obtained in the step (2) into an oil bath kettle at 160 ℃ for reaction for 8 h; the obtained product is washed by water centrifugal separation, thus obtaining the phase-transition ruthenium oxide.

The SEM of the phase-transition ruthenium oxide prepared in this example is shown in FIG. 4, and the morphology of the phase-transition ruthenium oxide is not much different from that of commercial ruthenium dioxide.

The XRD of the phase-transformed ruthenium oxide prepared in this example is shown in FIG. 5, and the diffraction peak thereof is changed as in example 1.

Example 3

(1) mixing 50mg of commercial ruthenium dioxide with 15mL of ethylene glycol solution, and performing ultrasonic treatment to obtain a black solution;

(2) putting the solution obtained in the step (1) into an oil bath kettle at 140 ℃ for reaction for 24 hours; the obtained product is washed by water centrifugal separation, thus obtaining the phase-transition ruthenium oxide.

The SEM of the phase-transition ruthenium oxide prepared in this example is shown in FIG. 6, and the surface of the phase-transition ruthenium oxide is rougher compared with commercial ruthenium dioxide.

The XRD of the phase-transformed ruthenium oxide prepared in this example is shown in fig. 7, and the XRD diffraction peak is shifted due to partial phase transformation, but the diffraction peak of the original ruthenium dioxide is partially retained. Although the phase transition rate is slow in the case of the reaction without adding a base, it is expected that the phase transition can be completed by increasing the temperature or the heating time.

Example 4

(1) mixing 50mg of commercial ruthenium dioxide with 15mL of glycerol, and performing ultrasonic treatment to obtain a black solution;

(2) placing the solution obtained in the step (1) in an oil bath pan at 160 ℃ and preserving heat for 20 hours; the resulting product was washed with water by centrifugation to obtain phase-converted ruthenium oxide.

XRD of phase-transformed ruthenium oxide prepared in this example is shown in FIG. 8, and since no base is added to the alcohol solution, the X-ray powder diffraction peak is substantially similar to that of example 1 by increasing the temperature and prolonging the heating time in order to transform the phase of ruthenium dioxide, thus illustrating the preparation of phase-transformed ruthenium oxide.

It is apparent that the above embodiments are only examples for clearly illustrating and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. It is not necessary or necessary to exhaustively enumerate all embodiments herein, and obvious variations or modifications can be made without departing from the scope of the invention.

Claims

1. A phase-converted ruthenium oxide characterized by: compared with the standard XRD pattern of ruthenium dioxide, a plurality of diffraction peaks of the standard XRD pattern shift slightly or generate new diffraction peaks, wherein the peak position corresponding to the (110) crystal face shifts 1.5-2 degrees leftwards from 27.5-28.5 degrees, the corresponding diffraction peak of the (101) crystal face disappears at 34.5-35.5 degrees, and 3 weaker new peaks are generated between 35.4-37.4 degrees.

2. The phase-converted ruthenium oxide according to claim 1, characterized in that: the peak width of a diffraction peak of a (211) crystal face in an XRD pattern of the diffraction grating is enlarged at 53.8-54.8 degrees, and a new diffraction peak is generated at a position shifted by 1.5-2.5 degrees on the left.

3. A method for preparing phase-transition ruthenium oxide is characterized in that: the method comprises the following steps:

(1) adding ruthenium dioxide into a solvent, and performing ultrasonic dispersion or stirring and dispersing uniformly; wherein the solvent is an alcohol; or the solvent is a mixed solution of alcohol and alkali;

(2) standing the solution obtained in the step (1) at 100-200 ℃ for 2-48 h to obtain the phase-converted ruthenium oxide.

4. The method for producing phase-converted ruthenium oxide according to claim 3, wherein: in the step (2), the ruthenium dioxide is rutile type powder.

5. The method for producing phase-converted ruthenium oxide according to claim 3, wherein: in the step (1), the alcohol is one or a mixture of several of methanol, ethanol, glycol and glycerol in any proportion; the alkali is one or a mixture of several soluble inorganic alkalis according to any proportion.

6. The method for producing phase-converted ruthenium oxide according to claim 3, wherein: the concentration range of hydroxide radicals in the alcoholic solution of the alkali in the step (1) is 0-3 mol/L.

7. The method for producing phase-converted ruthenium oxide according to claim 3, wherein: the dispersion concentration range of the ruthenium oxide in the solvent in the step (2) is 0.05-200 mg/mL.

8. The use of phase-converted ruthenium oxide according to claim 1 as electrocatalytic material in the electrolysis of water for the production of hydrogen.