CN117888141A - Platinum-modified tricobalt tetraoxide catalyst and preparation method and application thereof - Google Patents

Abstract

The present invention discloses a platinum-modified cobalt tetroxide catalyst and a preparation method and application thereof. The platinum-modified cobalt tetroxide catalyst comprises platinum and cobalt tetroxide; the platinum is loaded on the cobalt tetroxide; the platinum is in the form of micrometer spheres assembled from nanosheet platinum. The platinum-modified cobalt tetroxide catalyst provided by the present invention has excellent electrocatalytic performance, exhibits lower oxidation potential and higher glyceric acid selectivity in glycerol electrooxidation; the preparation method thereof is simple and easy to implement, and easy to expand production.

Description

A platinum-modified cobalt tetroxide catalyst and its preparation method and application

Technical Field

The present application relates to a platinum-modified cobalt tetroxide catalyst and a preparation method and application thereof, belonging to the technical field of catalytic materials.

Background technique

As a sustainable and clean energy source, _H2 is an indispensable part of future energy strategies. Water electrolysis is an effective way to produce clean and ultrapure hydrogen. However, limited by the slow reaction kinetics of the oxygen evolution reaction at the anode, the theoretical voltage of water decomposition is 1.23V. In addition, the oxygen produced at the anode is easily mixed with the _H2 produced at the cathode to cause explosion. Replacing the oxygen evolution reaction with organic oxidation is safe and economical, which can not only reduce the cell pressure, but also produce high value-added chemical products at the anode. Among them, glycerol is a by-product of biodiesel production. One ton of biodiesel can produce about 100kg of glycerol. In recent years, with the rapid development of the biodiesel industry, the output of glycerol has increased year by year, resulting in a sharp drop in the price of glycerol. However, glycerol is an important biomass resource that can be converted into a variety of high value-added chemical products such as glyceraldehyde, glyceric acid, hydroxymalonic acid, dihydroxyacetone, oxalic acid, lactic acid, glycolic acid and formic acid through oxidation, esterification, etherification, acidification and other processes. Compared with traditional thermal catalysis and microbial fermentation processes, electrocatalysis has many unique advantages in glycerol oxidation. First, the reaction is carried out at room temperature and pressure, which is environmentally friendly; second, the oxidation potential of glycerol is much lower than that of water; finally, the selectivity of the product can be controlled by regulating the catalyst and the electrocatalytic process. Therefore, it is crucial to develop catalysts with excellent glycerol electrooxidation performance.

Summary of the invention

The present application provides a platinum-modified cobalt tetroxide catalyst, wherein the platinum-modified cobalt tetroxide catalyst comprises platinum and cobalt tetroxide; the platinum is supported on the cobalt tetroxide;

The platinum is in the form of micron spheres assembled from nanosheet platinum. The platinum-modified cobalt tetroxide catalyst provided by the present invention has excellent electrocatalytic performance, exhibits lower oxidation potential and higher glyceric acid selectivity in glycerol electrooxidation; and its preparation method is simple and easy to implement, and easy to expand production.

According to the first aspect of the present application, a platinum-modified cobalt tetroxide catalyst is provided, wherein the platinum-modified cobalt tetroxide catalyst comprises platinum and cobalt tetroxide; the platinum is supported on the cobalt tetroxide;

The platinum is in the shape of micrometer spheres assembled from platinum nanosheets.

Optionally, the molar ratio of the platinum to the cobalt oxide is 0.5-10.

Optionally, the upper limit of the molar ratio of the platinum to the cobalt oxide is selected from 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, and the lower limit is selected from 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9.

Optionally, the platinum-modified cobalt oxide catalyst further includes a conductive substrate; the platinum-modified cobalt oxide catalyst is loaded on the surface of the conductive substrate.

Optionally, the masses of the platinum-modified cobalt oxide catalyst and the conductive substrate of the present invention can be adjusted according to actual needs.

The platinum-modified cobalt tetroxide catalyst provided by the present invention exhibits lower oxidation potential and higher glyceric acid selectivity in glycerol electrooxidation.

According to the second aspect of the present application, a method for preparing the above-mentioned platinum-modified cobalt tetroxide catalyst is provided, the preparation method comprising:

The solution containing the platinum compound is used as the electrolyte, and the cobalt oxide is used as the working electrode. Electrochemical deposition is performed to obtain the platinum-modified cobalt oxide catalyst.

Optionally, the electrochemical deposition is a constant potential electrochemical deposition.

Optionally, the platinum compound is chloroplatinic acid;

Preferably, the concentration of chloroplatinic acid in the electrolyte is 0.01-0.1M.

Optionally, the upper limit of the concentration of chloroplatinic acid in the electrolyte is selected from 0.1M, 0.08M, 0.06M, 0.04M, 0.02M, and the lower limit is selected from 0.01M, 0.02M, 0.04M, 0.06M, 0.08M.

Optionally, the deposition potential of the electrochemical deposition is -0.1 to -1 V; and the deposition time is 100 to 1800 s.

Optionally, the upper limit of the electrochemical deposition potential is selected from -1V, -0.8V, -0.6V, -0.4V, -0.2V, and the lower limit is selected from -0.1V, -0.8V, -0.6V, -0.4V, -0.2V.

Optionally, the upper limit of the deposition time of the electrochemical deposition is selected from 1800s, 1400s, 1000s, 800s, 600s, 400s, 200s, and the lower limit is selected from 100s, 1400s, 1000s, 800s, 600s, 400s, 200s.

Optionally, the electrochemical deposition is performed using a three-electrode mode.

Optionally, the cobalt tetroxide is prepared by the following method:

Step S1, a solution containing a cobalt salt is used as an electrolyte, a conductive substrate is used as a working electrode, and electrochemical deposition is performed in a three-electrode mode to obtain cobalt hydroxide;

Step S2, heat-treating the cobalt hydroxide to obtain the cobalt tetroxide;

Preferably, the cobalt salt is selected from cobalt nitrate.

Optionally, the electrochemical deposition is a constant potential electrochemical deposition.

Optionally, the concentration of the solution containing the cobalt salt is 0.01-0.4M.

Optionally, the upper limit of the concentration of the solution containing the cobalt salt is selected from 0.4M, 0.3M, 0.2M, 0.1M, 0.05M; the lower limit is selected from 0.01M, 0.3M, 0.2M, 0.1M, 0.05M.

Optionally, the conditions for electrochemical deposition in step S1 are: deposition potential of -0.5 to -1.5 V, and deposition time of 100 to 3600 s.

Optionally, in step S2, the heat treatment conditions are: heat treatment temperature is 300-600° C., and time is 0.5-8 h.

Optionally, the upper limit of the heat treatment temperature is selected from 600°C, 500°C, 400°C, and the lower limit is selected from 300°C, 400°C, 500°C.

Optionally, the upper limit of the heat treatment time is selected from 8h, 6h, 4h, 2h, 1h, and the lower limit is selected from 0.5h, 6h, 4h, 2h, 1h.

According to the third aspect of the present application, a method for preparing glyceric acid by electro-oxidation of glycerol is provided, the method comprising: using a platinum-modified cobalt tetroxide catalyst as a working electrode, Hg/HgO as a reference electrode, a graphite rod as a counter electrode, and a mixture containing glycerol as an electrolyte, and electro-oxidizing to obtain glyceric acid; the platinum-modified cobalt tetroxide catalyst is selected from the above-mentioned platinum-modified cobalt tetroxide catalyst.

The beneficial effects of this application include:

1) The platinum-modified cobalt tetroxide catalyst provided by the present invention has excellent electrocatalytic performance and exhibits a lower oxidation potential and a higher glyceric acid selectivity in glycerol electrooxidation.

2) The preparation method of the platinum-modified cobalt tetroxide catalyst provided by the present invention is simple and easy to implement, and easy to expand production.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

FIG1 is an X-ray diffraction (XRD) diagram of the platinum-modified cobalt tetroxide catalyst prepared in Example 1 of the present invention;

FIG2 is a scanning electron microscope (SEM) image of platinum-modified cobalt tetroxide prepared in Example 2 of the present invention;

FIG3 is a cyclic voltammetry (LSV) curve of platinum-modified cobalt tetroxide prepared in Example 3 of the present invention in 1M KOH and 0.1M glycerol electrolyte;

FIG. 4 shows the products of cobalt tetroxide modified with platinum under different voltages in Example 4 of the present invention.

Detailed ways

The present application is further described below in conjunction with specific embodiments. The following are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application discloses the following preferred embodiments, they are not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make some changes or modifications are equivalent to equivalent implementation cases and are within the scope of the technical solution.

Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources and used directly without any special treatment.

Unless otherwise specified, the analysis methods in the examples all adopt conventional settings and conventional analysis methods of instruments or equipment.

The preparation method of the platinum-modified cobalt tetroxide catalyst in the present application includes:

a) Cobalt tetroxide grows vertically on a conductive substrate, and platinum presents a micron-spherical structure assembled by nanosheets, and the micron-spherical platinum is loaded on the cobalt tetroxide array;

b) Platinum was loaded onto cobalt tetroxide by constant potential deposition.

Optionally, the molar ratio of platinum to cobalt oxide is 1:(0.1-2).

As a specific embodiment, the preparation method of the platinum-modified cobalt tetroxide catalyst in the present application includes:

Step A: using cobalt nitrate aqueous solution as electrolyte, adopting three-electrode mode, using self-supporting substrate (conductive substrate) as working electrode, graphite electrode as counter electrode and saturated calomel electrode as reference electrode, using constant potential method to deposit for a certain time to obtain Co(OH) ₂ ;

Step B: heat-treating Co(OH) ₂ in a muffle furnace to obtain cobalt tetroxide;

Step C: using chloroplatinic acid aqueous solution as electrolyte, adopting three-electrode mode, using cobalt tetroxide obtained in step B as working electrode, with counter electrode and reference electrode, and depositing for a certain time in a constant potential manner.

The analysis method in the embodiment of the present invention is as follows:

The linear sweep voltammetric curve was tested using a CHI 760E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.) with a voltage of -0.6 to 0.6 V (vs. Hg/HgO), a scan rate of 10 mV/s, and an electrolyte of a mixed solution of 1 M KOH and 0.1 M glycerol.

The product was detected by high performance liquid chromatography with 5 mM H ₂ SO ₄ as the mobile phase.

The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

Example 1

A 0.01M cobalt nitrate aqueous solution was prepared as an electrolyte, a saturated calomel electrode was used as a working electrode, a graphite rod was used as a counter electrode, and a carbon paper was used as a working electrode to form a three-electrode system. Deposition was performed by a constant potential method, the deposition voltage was -1V (vs.Hg/HgCl), the deposition time was 3600s, and then rinsed with deionized water. After vacuum drying, it was placed in a muffle furnace for heat treatment at a temperature of 300°C for 8h. After cooling, it was taken out as a working electrode, a platinum sheet was used as a counter electrode, a saturated calomel electrode was used as a working electrode, and a 0.1M chloroplatinic acid aqueous solution was used as an electrolyte. Deposition was performed by a constant potential deposition method, the deposition potential was -0.1V (vs.Hg/HgCl), and the time was 1800s. After completion, it was rinsed with deionized water and dried at room temperature to obtain platinum-modified cobalt tetroxide.

In this embodiment, the molar ratio of platinum to cobalt oxide is 1:0.2.

FIG1 is an XRD graph, from which it can be seen that there are both diffraction peaks of platinum and diffraction peaks of cobalt tetroxide, indicating that platinum-modified cobalt tetroxide has been successfully prepared.

Example 2

A 0.1M cobalt nitrate aqueous solution was prepared as an electrolyte, a saturated calomel electrode was used as a working electrode, a graphite rod was used as a counter electrode, and nickel foam was used as a working electrode to form a three-electrode system. Deposition was performed by constant potential method, the deposition voltage was -0.5V (vs.Hg/HgCl), the deposition time was 2400s, and then it was rinsed with deionized water. After vacuum drying, it was placed in a muffle furnace for heat treatment at a temperature of 400°C for 5h. After cooling, it was taken out as a working electrode, a platinum sheet was used as a counter electrode, a saturated calomel electrode was used as a working electrode, and a 0.05M chloroplatinic acid aqueous solution was used as an electrolyte. Deposition was performed by constant potential deposition method, the deposition potential was -0.5V (vs.Hg/HgCl), and the time was 1200s. After completion, it was rinsed with deionized water and dried at room temperature to obtain platinum-modified cobalt tetroxide.

In this embodiment, the molar ratio of platinum to cobalt oxide is 1:0.5.

FIG. 2 is a SEM image of platinum-modified cobalt tetroxide, from which it can be seen that the nanosheets are assembled into micron-shaped platinum loaded on the cobalt tetroxide array.

Example 3

A 0.2M cobalt nitrate aqueous solution was prepared as an electrolyte, a saturated calomel electrode was used as a working electrode, a graphite rod was used as a counter electrode, and a titanium sheet was used as a working electrode to form a three-electrode system. Deposition was performed by constant potential method, the deposition voltage was -1.5V (vs.Hg/HgCl), the deposition time was 100s, and then it was rinsed with deionized water. After vacuum drying, it was placed in a muffle furnace for heat treatment at a temperature of 500°C for 2h. After cooling, it was taken out as a working electrode, a platinum sheet was used as a counter electrode, a saturated calomel electrode was used as a working electrode, and a 0.01M chloroplatinic acid aqueous solution was used as an electrolyte. Deposition was performed by constant potential deposition method, the deposition potential was -1V (vs.Hg/HgCl), the time was 600s, and then it was rinsed with deionized water. After drying at room temperature, platinum-modified cobalt tetroxide was obtained.

In this embodiment, the molar ratio of platinum to cobalt oxide is 1:1.

Using platinum-modified cobalt tetroxide as the working electrode, Hg/HgO as the reference electrode, graphite rod as the counter electrode, and a mixed solution of 1 M potassium hydroxide and 0.1 M glycerol as the electrolyte, the linear sweep voltammetric curve was tested using a CHI760E electrochemical workstation (voltage range of -0.6 to 0.6 V (vs. Hg/HgO), scan rate of 10 mV/s). As shown in Figure 3, the voltage at a current density of 10 mA/cm2 was 0.42 V (vs. RHE), showing excellent glycerol electro-oxidation performance.

Example 4

A 0.04M cobalt nitrate aqueous solution was prepared as an electrolyte, a saturated calomel electrode was used as a working electrode, a graphite rod was used as a counter electrode, and a carbon cloth was used as a working electrode to form a three-electrode system. Deposition was performed by a constant potential method, the deposition voltage was -1.2V (vs. Hg/HgCl), the deposition time was 1200s, and then it was rinsed with deionized water. After vacuum drying, it was placed in a muffle furnace for heat treatment at a temperature of 600°C for 0.5h. After cooling, it was taken out as a working electrode, a platinum sheet was used as a counter electrode, a saturated calomel electrode was used as a working electrode, and a 0.08M chloroplatinic acid aqueous solution was used as an electrolyte. Deposition was performed by a constant potential deposition method, the deposition potential was -0.8V (vs. Hg/HgCl), and the time was 100s. After completion, it was rinsed with deionized water and dried at room temperature to obtain platinum-modified cobalt tetroxide.

In this embodiment, the molar ratio of platinum to cobalt oxide is 1:2.

The time-current curve was tested by CHI760E electrochemical workstation using platinum-modified cobalt oxide as the working electrode, Hg/HgO as the reference electrode, graphite rod as the counter electrode, and a mixed solution of 1M potassium hydroxide and 0.1M glycerol as the electrolyte. The voltage was selected as 0.5, 0.6 and 0.7V (vs. RHE) respectively. The product was quantitatively analyzed by high performance liquid chromatography, and the mobile phase was 5mMH ₂ SO ₄ . Figure 4 shows the products and their selectivity obtained under different voltages. It can be seen from the figure that the main product of glycerol electrooxidation is glyceric acid, and the selectivity is close to 70%.

The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims (10)

1. A platinum modified tricobalt tetraoxide catalyst, characterized in that the platinum modified tricobalt tetraoxide catalyst comprises platinum and tricobalt tetraoxide; the platinum is supported on the tricobalt tetraoxide;

the platinum is in a micron sphere shape assembled by nano-sheet platinum.

2. The platinum modified tricobalt tetraoxide catalyst according to claim 1, wherein the molar ratio of platinum to tricobalt tetraoxide is 0.5-10.

3. The platinum modified tricobalt tetraoxide catalyst according to claim 1 or 2, further comprising an electrically conductive substrate; the platinum modified cobaltosic oxide catalyst is loaded on the surface of the conductive substrate.

4. A method for preparing a platinum modified tricobalt tetraoxide catalyst according to any of claims 1 to 3, characterized in that said method comprises:

and (3) taking a solution containing a platinum compound as an electrolyte, taking cobaltosic oxide as a working electrode, and performing electrochemical deposition to obtain the platinum modified cobaltosic oxide catalyst.

5. The method of claim 4, wherein the electrochemical deposition is potentiostatic electrochemical deposition.

6. The production method according to claim 4, wherein the platinum compound is chloroplatinic acid;

preferably, the concentration of chloroplatinic acid in the electrolyte is 0.01-0.1M.

7. The method according to claim 4, wherein the electrochemical deposition has a deposition potential of-0.1 to-1V; the deposition time is 100-1800s.

8. The method of claim 4, wherein the electrochemical deposition is performed in a three electrode mode.

9. The method according to claim 4, wherein the tricobalt tetraoxide is prepared by the following method:

step S1, using a solution containing cobalt salt as an electrolyte, using a conductive substrate as a working electrode, and performing electrochemical deposition in a three-electrode mode to obtain cobalt hydroxide;

s2, performing heat treatment on the cobalt hydroxide to obtain the cobaltosic oxide;

preferably, the cobalt salt is selected from cobalt nitrate;

preferably, the electrochemical deposition is potentiostatic electrochemical deposition;

preferably, the concentration of the cobalt salt-containing solution is 0.01-0.4M;

preferably, the conditions of electrochemical deposition in step S1 are: the deposition potential is-0.5 to-1.5V, and the deposition time is 100-3600s;

preferably, in the step S2, the heat treatment conditions are as follows: the heat treatment temperature is 300-600 ℃ and the time is 0.5-8h.

10. A method for preparing glyceric acid by electrooxidation of glycerol, comprising: the platinum modified cobaltosic oxide catalyst is used as a working electrode, hg/HgO is used as a reference electrode, a graphite rod is used as a counter electrode, a mixture containing glycerol is used as an electrolyte, and glyceric acid is obtained through electrooxidation; the platinum modified tricobalt tetraoxide catalyst is selected from the platinum modified tricobalt tetraoxide catalysts of any of claims 1 to 3.