阅读说明：本技术 一种金属原子掺杂的电催化剂及其制备方法和应用 (Metal atom doped electrocatalyst and preparation method and application thereof ) 是由 周晓霞 陈航榕 于 2021-07-08 设计创作，主要内容包括：本发明涉及一种金属原子掺杂的电催化剂及其制备方法和应用。所述贵金属原子掺杂的电催化剂,包括：半导体和以氧化态的形式分布在半导体中的贵金属原子；所述半导体为SnO-2、TiO-2、CuO-x的至少一种；所述贵金属原子为Pt、Pd和Ag中的至少一种。(The invention relates to an electrocatalyst doped with metal atoms, a preparation method and application thereof. The noble metal atom-doped electrocatalyst, comprising: a semiconductor and noble metal atoms distributed in the semiconductor in the form of an oxidation state; the semiconductor is SnO 2 、TiO 2 、CuO x At least one of (a); the noble metal atom is at least one of Pt, Pd and Ag.)

1. A noble metal atom-doped electrocatalyst, comprising: a semiconductor and noble metal atoms distributed in the semiconductor in the form of an oxidation state; the semiconductor is SnO₂、TiO₂、CuO_xAt least one of (a); the noble metal atom is at least one of Pt, Pd and Ag.

2. The noble metal atom-doped electrocatalyst according to claim 1, wherein the content of the noble metal atoms is 0.1 to 1 wt%.

3. The noble metal atom-doped electrocatalyst according to claim 1 or 2, characterized in that the particle size of the noble metal atom-doped electrocatalyst is between 4 and 6 nm.

4. A method of preparing a noble metal atom-doped electrocatalyst according to any one of claims 1 to 3, comprising:

(1) dissolving a noble metal source in a mixed solution of water, ethylene glycol and polyvinylpyrrolidone (PVP) to obtain a noble metal source solution;

(2) carrying out hydrothermal pretreatment on the noble metal source solution to obtain a noble metal species solution with stable surfactant;

(3) adding a noble metal species solution stabilized by a surfactant into a semiconductor metal source solution, mixing, performing hydrothermal crystallization, filtering, washing, and freeze-drying to obtain the noble metal atom-doped electrocatalyst.

5. The production method according to claim 4, wherein the noble metal source is at least one of chloroplatinic acid, palladium nitrate and silver nitrate; the concentration of the noble metal source in the noble metal source solution stabilized by the surfactant is 1-5 mg/mL.

6. The method according to claim 4 or 5, wherein the volume ratio of the ethylene glycol to the water in the mixed solution of water, ethylene glycol and polyvinylpyrrolidone PVP is 1-20, and the concentration of polyvinylpyrrolidone PVP is 1-10 mg/mL.

7. The method according to any one of claims 4 to 6, wherein the temperature of the hydrothermal pretreatment is 150 ℃ to 200 ℃ and the time of the hydrothermal pretreatment is 5 minutes to 30 minutes.

8. The production method according to any one of claims 4 to 7, wherein the semiconductor metal source is at least one of tin chloride, titanium sulfate, and copper nitrate; the concentration of the semiconductor metal source in the semiconductor metal source solution is 1-10 mg/mL.

9. The method according to any one of claims 4 to 8, wherein the temperature of the hydrothermal crystallization is 150 to 200 ℃ and the time of the hydrothermal crystallization is 12 to 24 hours.

10. Use of a noble metal atom-doped electrocatalyst according to any one of claims 1 to 3 for electrolytic carbon dioxide reduction.

Technical Field

The invention relates to an electrocatalyst, a preparation method and application thereof, in particular to a metal atom doped electrocatalyst, a preparation method and application thereof, and particularly relates to a preparation method and application of a noble metal atom doped metal oxide semiconductor electrocatalyst, belonging to the field of electrocatalysts.

Background

With the acceleration of industrialization and the rapid development of human society, a large amount of fossil energy is consumed, and atmospheric CO is generated₂The content of (b) increases dramatically, triggering a series of energy crisis and environmental crisis. Excess CO₂Catalytic reduction to CH₄、HCOOH、CH₃OH、CH₃CH₂Chemical fuels such as OH are one of the important challenges facing the world and have important significance for renewable energy storage and environmental protection. Catalytic reduction of CO₂There are many methods, including thermocatalysis, photocatalysis, electrocatalysis, and more recently developed photoelectrocatalysis. How to efficiently remove CO under milder conditions₂The reduction to high value-added chemicals has been one of the research hotspots and difficulties in the field of catalysis.

The metal oxide is made of CO due to stable electrochemical performance, environmental protection and strong selectivity to formic acid₂Research on electrochemical reduction is hot. How to further improve the liquid-phase CO by regulating and controlling the electronic structure of the metal oxide₂The selectivity of the reduction product formic acid is of great significance.

Disclosure of Invention

In view of the above problems, the present invention aims to provide a preparation method and application of a noble metal atom doped metal oxide semiconductor electrocatalyst.

In one aspect, the present invention provides a noble metal atom-doped electrocatalyst, comprising: a semiconductor and noble metal atoms distributed in the semiconductor in the form of an oxidation state; the semiconductor is SnO₂、TiO₂、CuO_xAt least one of (a); the noble metal atom is at least one of Pt, Pd and Ag.

In the invention, the oxide semiconductor doped with noble metal atoms can utilize the doped noble metal atoms to regulate the electronic structure of the semiconductor and regulate CO₂The adsorption strength of the intermediate product on the electrocatalyst is reduced, and the selectivity of the target product formic acid is achieved.

Preferably, the content of the noble metal atoms is 0.1 to 1 wt%.

Preferably, the particle size of the noble metal atom-doped electrocatalyst is 4nm to 6 nm.

In another aspect, the present invention provides a method for preparing a noble metal atom-doped electrocatalyst, comprising:

(1) dissolving a noble metal source in a mixed solution of water, ethylene glycol and polyvinylpyrrolidone (PVP) to obtain a noble metal source solution;

(2) carrying out hydrothermal pretreatment on the noble metal source solution to obtain a noble metal species solution with stable surfactant;

(3) adding a noble metal species solution stabilized by a surfactant into a semiconductor metal source solution, mixing, performing hydrothermal crystallization, filtering, washing, and freeze-drying to obtain the noble metal atom-doped electrocatalyst.

In the present disclosure, the present invention obtains noble metal species (e.g., Pt, Ag, Pd, etc.) stabilized by a surfactant by hydrothermal pretreatment, and then obtains a noble metal atom-doped metal oxide semiconductor (e.g., SnO) by a hydrothermal crystallization method₂、TiO₂、CuO_xEtc.).

Preferably, the noble metal source is at least one of chloroplatinic acid, palladium nitrate and silver nitrate; the concentration of noble metal in the noble metal source solution stabilized by the surfactant is 1-5 mg/mL.

Preferably, the volume ratio of the ethylene glycol to the water in the mixed solution of the water, the ethylene glycol and the polyvinylpyrrolidone PVP is 1-20, and the concentration of the polyvinylpyrrolidone PVP is 1-10 mg/mL.

Preferably, the temperature of the hydrothermal pretreatment is 150-200 ℃, and the time of the hydrothermal pretreatment is 5-30 minutes.

Preferably, the semiconductor metal source is at least one of tin chloride, titanium sulfate and copper nitrate; the concentration of the semiconductor metal source in the semiconductor metal source solution is 1-10 mg/mL.

Preferably, the temperature of the hydrothermal crystallization is 150-200 ℃, and the time of the hydrothermal crystallization is 12-24 hours.

In a further aspect, the invention provides the use of a noble metal atom-doped electrocatalyst for electrolytic carbon dioxide reduction.

Has the advantages that:

the invention expands the application of the metal atom doped semiconductor in electrocatalysis, has simple synthesis method, provides a new solution for improving the selectivity of a target product, and the obtained electrocatalyst has excellent electrocatalysis activity and selectivity.

Drawings

FIG. 1 is an atomic Pt-doped SnO prepared in example 1₂(Pt atom/SnO₂) Spherical aberration electron micrographs of;

FIG. 2 is an illustration of atomic Pt-doped SnO prepared in examples 1 and 3₂(Pt atom/SnO₂) And Pt nanoparticle atom-supported SnO₂(PtNPS/SnO₂) XPS plot of Pt of (a);

FIG. 3 shows different samples prepared in examples 1-3 in electrochemical CO₂Products CO and H in reduction₂And faraday efficiency of HCOOH, where in each set of histograms, left: pt atom/SnO₂(ii) a The method comprises the following steps: SnO₂(ii) a And (3) right: pt NPs/SnO₂。

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the present disclosure, the electrocatalyst is a metal oxide semiconductor doped with noble metal atoms. Wherein the metal oxide semiconductor can be SnO₂、TiO₂、CuO_xAt least one of; the noble metal atom may be at least one of Pt, Ag, and Pd.

In an alternative embodiment, the noble metal atoms are 0.1 to 1wt% of the total mass. If the content of the noble metal is too high, the noble metal is easy to precipitate from the semiconductor oxide to form nano particles, and the CO is influenced₂Selectivity of the reduction product.

In the embodiment of the present invention, the electrocatalyst of the metal oxide semiconductor doped with noble metal atoms is obtained by subjecting the noble metal species obtained by the pretreatment and the metal oxide semiconductor precursor liquid to hydrothermal crystallization.

In SnO₂And a noble metal Pt as an example, the following exemplarily illustrates a preparation method of the electrocatalyst.

And (3) obtaining noble metal species stabilized by the surfactant by hydrothermal pretreatment. In particular. Weighing a certain amount of chloroplatinic acid, and dissolving the chloroplatinic acid in a mixed solution of deionized water, ethylene glycol and polyvinylpyrrolidone (PVP) to obtain a mixed solution 1. And (3) transferring the uniformly mixed solution 1 into a hydrothermal kettle, and carrying out hydrothermal reaction at the temperature of 150-200 ℃ for 5-30 min (if no hydrothermal pretreatment is carried out, Pt is easy to precipitate to form nanoparticles). And centrifuging and washing the product to remove the upper aqueous solution, thereby obtaining the noble metal Pt species stabilized by the surfactant. Wherein, the volume ratio of the ethylene glycol to the water can be 1-20, and the concentration of the polyvinylpyrrolidone PVP can be 1-10 mg/mL. The concentration of the noble metal precursor (noble metal source) in the mixed solution 1 can be 1-5 mg/mL.

And preparing the noble metal atom-doped metal oxide semiconductor by adopting a one-step hydrothermal crystallization method. Specifically, a semiconductor metal source is dissolved in water to obtain a semiconductor metal source solution. Then adding noble metal species stabilized by a surfactant, continuously stirring for a period of time, carrying out hydrothermal crystallization treatment, then filtering, washing, and freeze-drying to obtain the electrocatalyst noble metal atom Pt-doped semiconductor SnO₂(Pt atom/SnO₂). Wherein, the concentration of the semiconductor metal source can be 1-10 mg/mL. The temperature of the hydrothermal crystallization is 150-200 ℃, and the time of the hydrothermal crystallization is 12-24 h. The washing reagent is a mixed solution of acetone, ethanol and water. The drying mode is freeze drying, the freezing temperature can be-18 ℃, the freezing time is 4-8 hours, and the room temperature drying time is 8-12 hours.

The invention provides an atomic Pt-doped semiconductor, which utilizes atomic Pt to regulate and control the electronic structure of the semiconductor, improves the selectivity of electrochemical reduction of carbon dioxide and promotes the formation of formic acid which is a product of reduction of carbon dioxide.

It should be noted that other metal oxide and noble metal sources are suitable for use in the above-described method of preparing the electrocatalyst. The precious metal in the electrocatalyst obtained by the invention exists in the form of titanium oxide, and the electrocatalyst obtained is used in CO₂Exhibits excellent activity and high selectivity to the product formic acid.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

20mg of HPtCl₆·6H₂O dissolved in 10mL of ethylene glycol, 1mL of H₂O and 80mg PVP (K-40); then, the mixed solution is pretreated for 10min by water heating at 180 ℃; next, the mixture was cooled to room temperature, washed with acetone and n-hexane, and the upper aqueous solution was removed by centrifugal separation; finally, surfactant PVP stabilized Pt species (1mg/mL) was obtained.

500mg of SnCl₂·2H₂O dissolved in 50mL H₂Continuously stirring in O at 40 ℃ for 20 min; then 3mL of Pt species stabilized by PVP is added into the solution, and the solution is stirred strongly for 2h at 40 ℃; then transferring the solution into a hydrothermal kettle, and carrying out hydrothermal treatment at 180 ℃ for 16 h; finally, washing twice with acetone and normal hexane, washing once with distilled water, and freeze-drying overnight to obtain the final sample atom Pt-doped semiconductor SnO₂(Pt atom/SnO₂) The content of Pt atom was 0.1 wt%.

Example 2

500mg of SnCl₂·2H₂O is dissolved in 50mLH₂Continuously stirring in O at 40 ℃ for 20 min; then transferring the solution into a hydrothermal kettle, and carrying out hydrothermal treatment at 180 ℃ for 16 h; finally, washing twice with acetone and n-hexane, washing once with distilled water, and freeze-drying overnight to obtain the semiconductor SnO₂。

Example 3

Add 3mL of PVP protected Pt solution to 10mL of H₂O and NaBH₄300mg of SnO obtained in example 2₂Dissolving the powder in the solution, stirring vigorously at 80 deg.C for 6 hr, washing with acetone and n-hexane twice, washing with distilled water once, and drying at 300 deg.C overnight to obtain the final productTo Pt nanoparticle atom-supported SnO₂(Pt NPS/SnO₂)。

Example 4

The catalysts prepared in examples 1-3 were subjected to CO in a three-electrode system, CHI 660A electrochemical workstation (CH Instrument, Inc.)₂And (5) testing electrochemical reduction performance. Wherein Ag/AgCl is used as a reference electrode, a Pt sheet counter electrode, and a glassy carbon electrode coated with a catalyst is used as a working electrode. In electrochemical measurements, CO is used₂Saturated 0.1M KHCO₃The solution is used as electrolyte, and the catalytic performance of the material is tested under different potentials. The gas phase product was analyzed by gas chromatography and the liquid phase product by H-NMR.

FIG. 1 is a schematic representation of atomic Pt-doped SnO prepared in FIG. 1 as in example 1₂(Pt atom/SnO₂) Spherical aberration electron micrographs of; high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with aberration correction explores the atomic dispersion of Pt as shown in fig. 1. The bright spots in the samples show that Pt is dispersed in SnO in the form of titanium oxide₂No significant Pt nanoparticles were found. Further, the line scan intensity profile of the white dotted rectangle (inset in FIG. 1, with nm on the abscissa and x 10 on the ordinate)⁴) It has further been shown that atomically dispersed Pt can be doped into SnO₂In (1).

FIG. 2 is an illustration of atomic Pt-doped SnO prepared in examples 1 and 3₂(Pt atom/SnO₂) And Pt nanoparticle atom-supported SnO₂(Pt NPS/SnO₂) XPS graph of Pt (g). It can be found that: atomic Pt-doped SnO₂(Pt atom/SnO₂) Wherein Pt is substantially in the form of oxidation state, and Pt nanoparticles doped SnO₂(Pt NPs/SnO₂) Is substantially present in the form of metallic Pt; further, doping of atomic Pt can regulate the electronic structure of the metal oxide semiconductor, thereby affecting the valence state of Pt.

FIG. 3 shows different samples prepared in examples 1-3 in electrochemical CO₂Reduction on products CO, H₂And faraday efficiency of HCOOH. CO 2₂Only CO and H in reduction products₂And HCOOH. In the fixingAt a constant potential, CO on different samples was compared₂Faradaic efficiency of the reduction product. For pure SnO₂The faradaic efficiency of rhe on C product reached 60.3% at-1.1V vs. And Pt NPs/SnO₂In CO₂Less active in reduction, H₂Is the main reduction product. Encouraging, atomic Pt-doped SnO₂(Pt atom/SnO₂) In CO₂The activity in reduction is excellent. In all the catalysts prepared, Pt atom/SnO, whatever the potential employed₂The faradaic efficiency was highest for both the total C product and HCOOH, up to 93.7% and 78.4% for the total C product and the liquid product HCOOH, respectively, at-1.2V vs. Therefore, we believe that altering the chemical environment of the Pt species can largely modulate the selectivity of the product. For example, Pt nanoparticles are more prone to H formation₂While atom dispersed Pt favors CO₂Formation of HCOOH in the reduction. The main reason for this is Pt atom/SnO₂The active center of the medium metal oxygen (Pt-O) can regulate CO₂Adsorption and activation energy favour the adsorption of the intermediate HCOOH, resulting in high selectivity to HCOOH.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.