CN114408877A

CN114408877A - K-doped cuprous selenide nanosheet array structure material, preparation method and application thereof

Info

Publication number: CN114408877A
Application number: CN202210100667.3A
Authority: CN
Inventors: 吴正翠; 丁连春; 高峰
Original assignee: Anhui Normal University
Current assignee: Anhui Normal University
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2022-04-29
Anticipated expiration: 2042-01-27
Also published as: CN114408877B

Abstract

The invention provides a K-doped cuprous selenide nanosheet array structure material, a preparation method and application thereof. The preparation method comprises the following steps: obliquely placing the foamy copper in a mixed solution containing a selenium source, an alkali source, a reducing agent and an alkali metal salt, and carrying out hydrothermal reaction in a reaction kettle to prepare the foamy copper. The invention relates to K⁺Ion doping into Cu₂The Se nanosheets can effectively regulate the electron migration among atoms, and K transfers electrons to Se to generate Se sites rich in electrons, thereby realizing linear mode^*CO(^*CO_L) And bridge type^*CO(^*CO_B) The intermediate has strong adsorption effect and promotes the formation of C-C coupling^*COCHO intermediate for significantly improving electrocatalytic carbon dioxide reduction (CO)₂ER) catalytic activity to ethanol. Simultaneous doping with K⁺The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. Furthermore, doping with K⁺The ions improve the conductivity of the catalyst and increase the transfer rate of interface charges.

Description

K-doped cuprous selenide nanosheet array structure material, preparation method and application thereof

Technical Field

The invention belongs to the field of nano material preparation methods and electrocatalysis cross application, and particularly relates to a K-doped cuprous selenide nanosheet array structure material, a preparation method and application thereof.

Background

Electrocatalytic carbon dioxide reduction provides a sustainable approach to reduce greenhouse gas emissions. In CO₂C in the electroreduction product₂₊Product ratio C₁The product has higher energy density and higher value and is in the spotlight. Ethanol as CO₂Electroreduced liquid C₂The product is convenient to store and transport, and is widely used as a raw material for producing solvents, organic chemicals and disinfectants. However, due to the difficulty of C-C coupling and ethanol production with other C' s₂₊Product competition, currently highly active and selective electrocatalysis of CO₂The catalyst for reduction to ethanol product is still rare. Therefore, the development of highly active, selective and stable CO₂It is critical that the electro-reduction catalyst selectively drives the C-C coupling to form ethanol.

It is well known that copper is the only energy to produce C₂₊The product is a single metal catalyst. However, the overpotential of copper metal is high, the variety of products is large, C₂₊The product selectivity is low. Furthermore, copper-based materials have a lower energy barrier and higher reaction kinetics for Hydrogen Evolution Reactions (HER), while C₂₊The products are generally produced in a more negative potential range, which inevitably leads to more hydrogen evolution side reactions. Different nanostructures of copper chalcogenides have been applied to CO₂In the electroreduction, the S or Se element in the composition can improve the catalytic activity, but is mostly limited to C₁And (3) obtaining the product.

Cuprous selenide (Cu) in the prior art₂Se) catalyst has complex preparation method and high preparation cost, and the problems of low activity, poor selectivity, poor stability and the like of the electrocatalytic carbon dioxide reduction still limit the development and application of the electrocatalytic carbon dioxide reduction.

Disclosure of Invention

The invention aims to provide a K-doped cuprous selenide nanosheet array structure material and a preparation method thereof, and K-doped Cu with foamy copper as a conductive substrate is prepared through one-step liquid phase reaction₂Se nanosheet array structure material.

The invention also aims to provide application of the K-doped cuprous selenide nanosheet array structure material in electrocatalysis of CO₂And (4) carrying out reduction reaction. Material prepared according to the invention, Cu₂Se nano sheetThe exposed (220) crystal face is favorable^*And (4) adsorbing the CO intermediate. K⁺Ion doping into Cu₂Cu can be better protected in Se crystal lattice⁺Species, at the same time enhance^*The bonding strength of the CO intermediate is favorable for subsequent C-C coupling, and the electrocatalysis of CO is accelerated₂Conversion to ethanol, enhanced catalyst electrocatalysis of CO₂Activity, selectivity and stability of reduction to ethanol.

The specific technical scheme of the invention is as follows:

a preparation method of a K-doped cuprous selenide nanosheet array structure material comprises the following steps:

obliquely placing the foamy copper in a mixed solution containing a selenium source, an alkali source, a reducing agent and potassium salt, and carrying out hydrothermal reaction in a reaction kettle to prepare the K-doped cuprous selenide nanosheet array structure material.

The preparation method of the mixed solution containing the selenium source, the alkali source, the reducing agent and the potassium salt comprises the following steps: dissolving selenium source, alkali source, reducing agent and potassium salt in water, and stirring to obtain a mixed solution.

The water is preferably deionized water, and the volume of the water is 20-35 mL.

The ratio of the selenium source to the potassium salt is 3:1-3, preferably 3: 2.

The ratio of the selenium source to the alkali source to the reducing agent is as follows: 3:500-2500:5-25.

The addition amount of the alkali source is 50 to 250mmol, preferably 150 mmol.

The addition amount of the reducing agent is 0.5-2.5mmol, preferably 1.5 mmol.

The concentration of the selenium source in the mixed solution is 0.008-0.015M;

the selenium source is selenium powder (Se);

the alkali source is sodium hydroxide (NaOH);

the reducing agent is sodium borohydride (NaBH)₄)；

The potassium salt is potassium bromide (KBr).

The hydrothermal reaction is carried out for 5-7h at 100-140 ℃, preferably for 6h at 120 ℃.

The foam copper is required to be cleaned before use, and the specific cleaning method comprises the following steps: soaking in 6M hydrochloric acid for 15min to remove surface oxide film, cleaning with deionized water and anhydrous ethanol, and cutting into 2 × 3cm size.

The hydrothermal reaction is carried out in a stainless steel reaction kettle with a polytetrafluoroethylene lining.

Further, in the preparation method, after the hydrothermal reaction is finished, the mixture is naturally cooled to room temperature, washed and dried to obtain the catalyst.

The washing is as follows: washing with deionized water for 3-5 times, and washing with anhydrous ethanol for 3-5 times.

The drying comprises the following steps: drying at 60 ℃ in a vacuum drying oven for 12 h.

In the preparation process, the foam copper is obliquely arranged, so that a sample can uniformly grow on two sides of the foam copper.

The invention provides a K-doped cuprous selenide nanosheet array structure material and K-doped Cu prepared from the material₂The Se nanosheet array structure material is a nanosheet array with the transverse dimension of 300-1300 nm.

The invention provides an application of a K-doped cuprous selenide nanosheet array structure material as an electrocatalytic carbon dioxide reduction reaction (CO)₂ER) electrocatalyst.

The K-doped cuprous selenide nanosheet array structure material is used for electrocatalytic carbon dioxide reduction reaction (CO)₂ER) electrocatalyst is applied, and the specific application method is as follows: cutting the K-doped cuprous selenide nanosheet array structure material into 0.5 multiplied by 0.5cm as a working electrode, respectively using a carbon rod and an Ag/AgCl electrode as a counter electrode and a reference electrode, and using 0.1M KHCO electrolyte₃Solution, electrochemically tested in a two-electrode cell using CHI 760E electrochemical workstation; by saturating CO₂0.1M KHCO₃Testing of Faraday efficiency of ethanol under LSV polarization curve and different voltages in electrolyte by CO₂ER properties. For comparison, 0.1M KHCO saturated with Ar was investigated₃K-doped Cu in electrolyte₂LSV polarization curve of Se nano sheet array structure material. Linear scanning polarization curve (LSV) at 5.0mV · s^-1Scanning speed ofAt a low rate. Stability was obtained by measuring the current density time curve at constant voltage. Electrochemically active area (ECSA) was determined by scanning in the absence of distinct faraday regions and at different scan rates (6, 7, 8, 9, 10, 11 and 12mV · s)^-1) Electrochemical double-layer capacitance (C) measurement by cyclic voltammetry_dl) Evaluation was performed with a test voltage ranging from-0.08 to 0.02V (relative reversible hydrogen electrode); electrochemical Impedance (EIS) was tested at a frequency range of 100kHz to 0.01Hz and at-0.2V (relative reversible hydrogen electrode).

The inventors found that addition of alkali metal cations to the electrolyte solution enabled adsorption on the surface of the Cu electrode, since^*The CO intermediate and alkali metal cations in the electrochemical double layer generate local electric field interaction to remarkably promote^*CO is adsorbed, and the coverage of the CO on the surface of the catalyst is increased. The inventor researches and researches to dope alkali metal cations into the crystal lattice of the Cu chalcogenide, adjust the electronic structure and active sites of the catalyst and optimize the catalyst^*And the CO intermediate and other ethanol intermediates are adsorbed on the surface of the catalyst, so that an ethanol product is effectively generated. There are no reports in the prior art of doping alkali metal cations into the Cu chalcogenide lattice for electrocatalytic carbon dioxide reduction.

In the preparation method, O in which copper on the surface of the foam copper is dissolved in solution is utilized by a simple one-step chemical liquid phase synthesis method₂Oxidation to form Cu²⁺Ions with OH in solution^-Binding to form Cu (OH)₂Further conversion to Cu (OH) in the presence of excess base (NaOH)₄ ^2-Ions, subsequently being gradually bound by BH in solution₄ ^-Reduction of ions to form Cu⁺Ions. Selenium powder is dissolved by BH in strong alkaline (NaOH) condition₄ ^-Ion fast reduction to form Se₂ ^2-Is ionized, and is further subjected to an excess of BH₄ ^-Reduction of ions to form Se^2-Ions. Cu⁺Ions with Se^2-Ion reaction to form cubic phase Cu₂Seed crystals of Se. Planar quadrilateral Cu (OH) present in solution₄ ^2-Adsorption on Cu₂(220) plane of Se seed crystal, inducing the seed crystal to grow gradually in orientationCuprous selenide nanosheets exposed on (220) crystal face and K in solution⁺Ion doping to Cu₂In the crystal lattice of Se, a K-doped cuprous selenide nanosheet array structure material growing on the foamy copper is formed.

In the present invention, K is doped with Cu₂The electronic structure of the catalyst is optimized by the Se nanosheets, and the electronic interaction between atoms is adjusted. By transferring electrons to Se via K, generating Se sites rich in electrons, and electrostatically adsorbing CO₂The molecule forms Se-C bond to promote linear CO₂Conversion to bending adsorbed on Se sites^*CO₂ ^–An intermediate. Further reduced to positively charged linear form adsorbed on Se sites by a Proton Coupled Electron Transfer (PCET) step^*CO_LIntermediates and negatively charged bridge adsorbed on Cu sites^*CO_BAn intermediate.^*CO_BFurther reduction of the intermediate to form^*CHO intermediates, and^*CO_Lcoupling of intermediates to adsorption on Cu sites^*The COCHO intermediate is subjected to a plurality of proton coupling electron transfer steps,^*converting COCHO intermediate into O end adsorbed on Cu site^*OCH₂CH₃Intermediate, finally by protonation to ethanol (C)₂H₅OH)。K⁺Ion doping enhances the linear type^*CO_LIntermediate body and bridge^*CO_BThe adsorption strength of the intermediate and can better protect Cu in the electrocatalysis process₂Cu in Se⁺Species, extend the retention time of carbon-containing intermediates on the catalyst surface, promote C-C coupling formation^*COCHO intermediates, enhanced electrocatalytic CO₂Catalytic activity for reduction to ethanol. Simultaneous doping with K⁺The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. Furthermore, K⁺The ion doping improves the conductivity of the catalyst and obviously increases the transfer rate of interface charges. The material is therefore in potassium bicarbonate (KHCO)₃) To electrocatalysis of CO in electrolyte₂The reduction to ethanol shows excellent activity, selectivity and stability, and the electrocatalysis of CO₂By reduction to ethanolIs very valuable in practical application. The invention provides an electrocatalytic carbon dioxide reduction reaction (CO)₂ER) has the characteristics of low overpotential, high selectivity, good stability, simple preparation process, environmental friendliness and low cost of the produced ethanol product.

Drawings

FIG. 1 shows K-doped Cu prepared in example 1₂An X-ray powder diffraction (XRD) pattern of the Se nanosheet array structure material;

FIG. 2 shows K-doped Cu prepared in example 1₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 3 shows K-doped Cu prepared in example 1₂Energy dispersive X-ray (EDX) spectroscopy of the Se nanosheet array structure material;

FIG. 4 shows K-doped Cu prepared in example 1₂A Transmission Electron Microscope (TEM) image of the Se nanosheet array structure material;

FIG. 5 shows K-doped Cu prepared in example 1₂A high resolution lattice fringe (HRTEM) image of the Se nanosheet array structure material;

FIG. 6 shows K-doped Cu prepared in example 1₂A Raman spectrum (Raman) diagram of the Se nanosheet array structure material;

FIG. 7 shows K-doped Cu with K doping percentages of 5.9% and 15.9% prepared in example 2₂An energy dispersive X-ray spectroscopy (EDX) map of the Se nanosheet array structure material;

FIG. 8 shows the K-doped Cu of 5.9 wt% K doping prepared in example 2₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 9 shows the preparation of K-doped Cu of 15.9% by weight percentage of K-doping in example 2₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 10 shows K-doped Cu of different K contents (5.9%, 11.2% and 15.9%) prepared in example 1 and example 2₂Se and undoped Cu prepared in example 3₂Electrocatalytic carbon dioxide reduction (CO) reaction with Se nanosheet array structure₂ER) of the LSV curve;

FIG. 11 shows K-doped Cu prepared in examples 1 and 3₂Se nanosheet and undoped Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) faradaic efficiency plot of the product;

FIG. 12 shows K-doped Cu prepared in example 2₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) faradaic efficiency plot of the product;

FIG. 13 shows K-doped Cu in example 1₂Electrocatalysis carbon dioxide reduction reaction (CO) of Se nanosheet array structure material₂ER) current density time plot;

FIG. 14 shows K-doping of Cu in examples 1 and 2₂Se nanosheet array structure material and undoped Cu in example 3₂Electrocatalysis carbon dioxide reduction reaction (CO) of Se nanosheet array structure material₂ER) capacitance current graph;

FIG. 15 shows K-doping of Cu in examples 1 and 2₂Se nanosheet array structure material and undoped Cu in example 3₂Electrocatalysis carbon dioxide reduction reaction (CO) of Se nanosheet array structure material₂ER) impedance plot;

FIG. 16 shows K-doped Cu in example 1₂The Se nanosheet array structure material electrocatalysis carbon dioxide reduction reaction (CO) at-0.8V potential₂ER) in situ ir spectrogram over time;

FIG. 17 shows the reaction time of 4h for K-doped Cu prepared in example 4₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 18 shows the reaction time of 8h for K-doped Cu prepared in example 4₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 19 shows K-doped Cu prepared in example 4 with reaction times of 4h and 8h₂An X-ray powder diffraction (XRD) pattern of the Se nanosheet array structure material;

FIG. 20 shows K-doped Cu prepared in example 4 with reaction time of 4h or 8h₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) (LSV curve of sample prepared in example 1 with reaction time of 6h added as control).

FIG. 21 shows K-doped Cu prepared in example 5 with a reaction temperature of 80 ℃₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 22 shows K-doped Cu prepared in example 5 with a reaction temperature of 160 deg.C₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 23 shows K-doped Cu prepared in example 5 at 80 ℃ or 160 ℃₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) (LSV curve of the sample prepared at reaction temperature of 120 ℃ in example 1 added as control);

FIG. 24 is a SeO prepared in example 6₂K-doped Cu as selenium source₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 25 is a SeO prepared in example 6₂K-doped Cu as selenium source₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) (LSV curve of the sample prepared by using Se powder as selenium source in example 1 added in the figure as control);

FIG. 26 shows the addition of 20mmol of K-doped Cu as NaOH in example 7₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 27 shows the addition of 280mmol of K-doped Cu as NaOH prepared in example 7₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 28 shows the addition of 20mmol or 280mmol of K-doped Cu as NaOH prepared in example 7₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) (LSV curve of sample prepared by adding 150mmol of example 1NaOH as control);

FIG. 29 shows NaBH prepared in example 8₄K-doped Cu in an amount of 0.2mmol₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 30 shows Na prepared in example 8BH₄K-doped Cu in an amount of 2.8mmol₂A Scanning Electron Microscope (SEM) image of the Se nanostructure material;

FIG. 31 is NaBH prepared in example 8₄Adding K-doped Cu in an amount of 0.2mmol or 2.8mmol₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) LSV curve (adding example 1NaBH to the graph)₄LSV curve of sample prepared with 1.5mmol addition as control);

FIG. 32 shows K-doped Cu with KCl as potassium source prepared in example 9₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 33 shows KHCO being the potassium source prepared in example 9₃K doped with Cu of₂A Scanning Electron Microscope (SEM) image of the Se nanosheet array structure material;

FIG. 34 shows KCl or KHCO as the potassium source prepared in example 9₃K doped with Cu of₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) (LSV curve of the sample prepared in example 1 with KBr as potassium source added as control).

Detailed Description

The invention is described in detail below with reference to the following examples and the accompanying drawings.

Example 1

K-doped Cu₂The preparation method of the Se nanosheet array structure material comprises the following steps:

soaking a piece of foamy Copper (CF) with the area of 2 x 3cm in 6M hydrochloric acid for 15min, and then washing with deionized water and absolute ethyl alcohol for 3 times respectively for later use; accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH₄150mmol NaOH and 0.2mmol KBr are added into the small beaker to form a mixed solution, the mixed solution is stirred for 30min to obtain a uniform wine red solution, the solution is transferred into a stainless steel reaction kettle with a lining of 50mL polytetrafluoroethylene, the pretreated foamy copper is obliquely placed into the stainless steel reaction kettle, and the reaction is carried out in a drying oven at 120 ℃ for 6 h. Naturally cooling to room temperature after the reaction is finished, and covering the foam copper covered by the black sample with deionized water andwashing with anhydrous ethanol for 3 times, drying the obtained sample in a vacuum drying oven at 60 deg.C for 12 hr to obtain K-doped Cu₂Se nanosheet array structure material.

Structural and morphological characterization of the product:

the final product obtained in example 1 was subjected to phase identification by X-ray powder diffractometry (XRD). As shown in FIG. 1, all diffraction peaks are associated with the cubic phase Cu₂Se (JCPDS No. 65-2982).

The product obtained in example 1 was subjected to morphological analysis by Scanning Electron Microscopy (SEM). As shown in FIG. 2, the sample is a nanosheet array structure with uniform distribution, and the transverse dimension of the nanosheet is 300-400 nm.

The final product composition of example 1 was analyzed by energy dispersive X-ray (EDX) spectroscopy. As shown in FIG. 3, the atomic percentages of the Cu, Se, and K elements are 34.94:18.21: 12.11. The mass percentage of K element was thus calculated to be 11.2%, whereby the product of example 1 was written as K_11.2％-Cu₂Se。

The product of example 1 was analyzed for morphology using Transmission Electron Microscopy (TEM). As shown in fig. 4, the sample was a flexible nanosheet structure.

The crystal planes of the product of example 1 were characterized using a High Resolution Transmission Electron Microscope (HRTEM). As shown in FIG. 5, the lattice fringes with a interplanar spacing of 0.205nm correspond to Cu₂The (220) plane of Se.

The vibration modes of the product obtained in example 1 were characterized by raman spectroscopy. As shown in FIG. 6, the Raman spectrum was at 271 cm^-1A peak appears corresponding to Cu₂Cu-Se vibration of Se.

Example 2

accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH₄150mmol NaOH, 0.1mmol or 0.3mmol KBr was added to the above small beaker, stirred for 30min to obtain a wine red homogeneous solution, which was transferred to 50mL Teflon lined stainless steelThe copper foam was treated in a kettle in the same manner as in example 1, and the pretreated copper foam was placed in the solution in a slant and reacted in an oven at 120 ℃ for 6 hours. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the addition amount of KBr is 0.1mmol, K-doped Cu with the K doping amount of 5.9 percent is obtained₂Se nanosheet array structure material; when the addition amount of KBr is 0.3mmol, K-doped Cu with the K doping amount of 15.9 percent is obtained₂Se nanosheet array structure material.

The product composition of example 2 was analyzed using energy dispersive X-ray spectroscopy (EDX). As shown in fig. 7, the atomic percentages of Cu, Se, and K elements were 30.20:16.32:5.44 and 24.37:11.50:11.47, respectively, and the mass percentages of K elements were calculated to be 5.9% and 15.9%, respectively. The product of example 2 is hereby written as K_5.9％-Cu₂Se and K_15.9％-Cu₂Se。

The morphology of the sample of example 2 was further analyzed using a Scanning Electron Microscope (SEM). FIG. 8 and FIG. 9 are each K_5.9％-Cu₂Se nanosheet array and K_15.9％-Cu₂And SEM images of the Se nanosheet array show that the sample is an array structure formed by the interconnected nanosheets. Wherein the nano-sheet has a transverse average size of 300nm at a K doping amount of 5.9% (FIG. 8). At a K doping level of 15.9%, the nanosheets had an average transverse dimension of 410nm (fig. 9).

Example 3

K-doped Cu₂Se nanosheet array structure material used as electrocatalytic carbon dioxide reduction reaction (CO)₂ER) catalyst.

The specific application method comprises the following steps: cu doped with K having an area of 0.5X 0.5cm₂Se nanosheet array structure material is used as a working electrode, a carbon rod and an Ag/AgCl electrode are respectively used as a counter electrode and a reference electrode, and the concentration of the active carbon in the solution is 0.1M KHCO₃Electrochemical testing was performed in the electrolyte using the CHI 760E electrochemical workstation at room temperature (25 ℃); linear Sweep Voltammetry (LSV) at 5.0mV · s^-1Obtaining a polarization curve according to the scanning speed; by at saturationCO₂0.1M KHCO₃Testing of Faraday efficiency of ethanol under LSV polarization curve and different voltages in electrolyte by CO₂ER properties.

Under the same conditions as above, with Cu₂The Se nanosheets are used as working electrodes for testing and used as comparative experiments. Wherein Cu₂Se nanosheet is prepared by omitting KBr in the raw material on the basis of example 1, and is defined as Cu₂Se。

FIG. 10 shows K-doped Cu with K doping amounts of 5.9%, 11.2% and 15.9% prepared in examples 1, 2 and 3₂Se and undoped Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) LSV polarization curve. As can be seen from the figure, K_11.2％-Cu₂The current density of the Se nano-sheet array structure material reaches 97.6 mA-cm under the potential of-1.3V^-2Higher than K_5.9％-Cu₂Se(76.1mA·cm^-2)，K_15.9％-Cu₂Se(83.2mA·cm^-2) And undoped Cu₂Se (66.2mA·cm^-2) (ii) a Indicating K doping with Cu₂The sample activity of Se is better than that of undoped Cu₂Se, K doping percentage by weight significantly affects the electrocatalytic carbon dioxide reduction (CO)₂ER) activity, the activity of the sample with a percentage of K doping of 11.2% is better than the activity of the samples with doping amounts of 5.9% and 15.9%.

FIG. 11 is K_11.2％-Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) product, giving a graph of Faraday efficiency for comparison with undoped Cu₂Se for CO₂Faradaic efficiency plot of ER products. K_11.2％-Cu₂Under the potential of-0.8V, the Faraday efficiency of the Se nanosheet array structure material for producing ethanol can reach 70.3 percent, which is much higher than that of the Se nanosheet array structure material without doping Cu₂12.1% of Se. FIG. 12 is K_5.9％-Cu₂Se and K_15.9％-Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) faradaic efficiency plot of the product. K_5.9％-Cu₂Se nano sheet array structure material is in-0Faradaic efficiency for ethanol production at a potential of 8V was maximal at 27.6%. K_15.9％-Cu₂The Faraday efficiency of the Se nanosheet array structure material for producing ethanol at-0.9V potential is 46.0% at the maximum.

FIG. 13 is K_11.2％-Cu₂Evaluation of electrocatalytic carbon dioxide reduction reaction (CO) by Se nanosheet array structure material at-0.8V potential₂ER) stability of the current density time curve. After 12h of testing, the current density remained above 97% of the initial value, indicating K_11.2％-Cu₂The Se nanosheet array structure material has excellent electrocatalytic carbon dioxide reduction reaction (CO)₂ER).

FIG. 14 shows electrocatalytic carbon dioxide reduction (CO) at different sweep rates₂ER) capacitance current graph. K_11.2％-Cu₂The electric double layer capacitance of the Se nanosheet array structure material is 37.1mF cm^-2Greater than Cu₂20.7 mF-cm of Se^-2，K_5.9％-Cu₂24.4 mF-cm of Se^-2And K_15.9％-Cu₂27.1 mF-cm of Se^-2. Therefore, the electrocatalytic carbon dioxide reduction reaction (CO) of the material can be increased after K is doped₂ER), moderate doping amount of K_11.2％-Cu₂The Se nanosheet array structure material has the largest electrochemical active area.

FIG. 15 shows an electrocatalytic carbon dioxide reduction reaction (CO)₂ER) condition. The semi-circle diameter of the sample after K doping is all larger than that of the undoped Cu₂Se is small, wherein K_11.2％-Cu₂The smallest semicircle diameter of the Se sample shows that the resistance of the catalyst can be obviously reduced after the K is doped, and the catalytic dynamics of the electrocatalytic carbon dioxide reduction reaction is accelerated.

FIG. 16 is K_11.2％-Cu₂The Se nanosheet array structure material electrocatalysis carbon dioxide reduction reaction (CO) at-0.8V potential₂ER) was varied with time (measured every 2min until 14min when the intermediate was unchanged. To investigate the retention time of the intermediate, an in situ infrared spectrum of 2h was also tested. ) In situ infrared spectroscopy. At the beginning of the reactionBridged with prolonged reaction time^*CO_BLine-merging type^*CO_LThe intermediate body shifts to a high wavenumber, and^*OH intermediate shifts to lower wavenumbers, indicating bridge formation^*CO_BLine-merging type^*CO_LThe adsorption of the intermediate on the surface of the catalyst is enhanced, and^*the adsorption of OH is reduced, thereby promoting the electrocatalytic carbon dioxide reduction (CO)₂ER) and inhibits the competitive Hydrogen Evolution Reaction (HER). After 2 hours of electrolysis, K_11.2％-Cu₂All intermediates on Se are kept unchanged, which shows that K doping can enable the surface of the catalyst to retain the carbon-containing intermediates for a long time, and is beneficial to C-C coupling to generate ethanol.

Through the comparison, the invention can obtain that K is⁺Ion doping into Cu₂The Se nanosheets can effectively regulate the electron migration among atoms, and K transfers electrons to Se to generate Se sites rich in electrons, thereby realizing linear mode^*CO(^*CO_L) And bridge type^*CO(^*CO_B) The intermediate has strong adsorption effect and promotes the formation of C-C coupling^*COCHO intermediates, enhanced electrocatalytic carbon dioxide reduction (CO)₂ER) catalytic activity to ethanol. Simultaneous doping with K⁺The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. Furthermore, doping with K⁺The ions improve the conductivity of the catalyst and significantly increase the transfer rate of interfacial charges. The K-doped cuprous selenide (Cu)₂Se) nanosheet array structure material in potassium bicarbonate (KHCO)₃) Electrocatalytic reduction of carbon dioxide (CO) in an electrolyte₂ER) synthetic ethanol has the characteristics of high activity, good selectivity and excellent stability. The invention has simple preparation process and low cost, and can be used for electrocatalytic carbon dioxide reduction (CO)₂ER) to ethanol is of great value for practical applications.

Example 4

accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of Na powderBH₄150mmol NaOH and 0.2mmol KBr were added to the above beaker, stirred for 30min to obtain a wine red homogeneous solution, the solution was transferred to a 50mL stainless steel reactor lined with Teflon, copper foam was treated according to the method of example 1, the pretreated copper foam was placed in the solution in a slant and reacted in an oven at 120 ℃ for 4h or 8 h. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the reaction time is 4h, thin-film K-doped Cu which is not completely grown into nanosheets is obtained₂A Se nanostructure material; when the reaction time is 8h, K-doped Cu with the transverse average size of 800nm is obtained₂Se nanosheet array structure material.

FIG. 17 is K doped Cu with reaction time of 4h₂Scanning Electron Microscope (SEM) images of Se nanostructured materials. Indicating that the sample is interconnected film-like nanostructures that have not been fully grown.

FIG. 18K doped Cu with reaction time of 8h₂Scanning Electron Microscope (SEM) images of Se nanosheet array structure materials. The sample is shown to be an array structure formed by connecting large and thick nano sheets, and the average transverse dimension of the nano sheets is 800 nm.

FIG. 19 is K doped Cu with reaction times of 4h and 8h₂X-ray powder diffraction (XRD) pattern of Se nanostructured material. When the reaction time is 4h, except for Cu₂Se diffraction peak also shows precursor Cu (OH)₂The diffraction peak of (A) indicates that the reaction was incomplete and not completely converted into Cu at a reaction time of 4 hours₂And (5) Se. When the reaction time is 8h, only Cu is present₂Diffraction peak of Se.

FIG. 20K doped Cu with reaction times of 4h and 8h₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array material₂ER) polarization curve (LSV curve of sample prepared in example 1 with reaction time of 6h was added as control). As can be seen from the figure, the current density of the sample with the reaction time of 6h reaches 97.6mA cm under the potential of-1.3V^-2Higher than the sample (34.5mA cm) with a reaction time of 4 hours^-2) And a reaction time of 8h sample (46.6mA cm)^-2). Shows that the synthetic K is doped with Cu₂The reaction time of the Se nanosheet array material significantly affects the electrocatalytic carbon dioxide reduction (CO)₂ER) activity, the reaction time is 6h, the active site of the sample is the most, and the electrocatalytic carbon dioxide reduction reaction (CO) is carried out₂ER) activity was superior to samples with reaction times of 4h and 8 h.

Example 5

soaking a piece of foamy Copper (CF) with the area of 2 x 3cm in 6M hydrochloric acid for 15min, and then washing with deionized water and absolute ethyl alcohol for 3 times respectively for later use; accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH₄150mmol NaOH and 0.2mmol KBr are added into the small beaker, stirred for 30min to obtain a uniform wine red solution, the solution is transferred into a stainless steel reaction kettle with 50mL polytetrafluoroethylene as a lining, the pretreated foamy copper is obliquely placed into the stainless steel reaction kettle, and the reaction is carried out for 6h in an oven at 80 ℃ or 160 ℃. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the reaction temperature is 80 ℃, thin-film K-doped Cu consisting of nano particles is obtained₂A Se nanostructure material; the K-doped Cu with the transverse average size of 400nm is obtained at the reaction temperature of 160 DEG C₂Se nanosheet array structure material.

FIG. 21 is K doped Cu with a reaction temperature of 80 deg.C₂Scanning Electron Microscope (SEM) images of Se nanostructures. The sample is shown as a thin film structure composed of nanoparticles.

FIG. 22 is K doped Cu with a reaction temperature of 160 deg.C₂Scanning Electron Microscope (SEM) images of Se nanostructures. The sample is shown to be an array structure formed by connecting thicker nano sheets, and the average transverse dimension of the nano sheets is 400 nm.

FIG. 23 is K doped Cu with reaction temperatures of 80 ℃ and 160 ℃₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) LSV polarization curve (LSV curve of sample prepared at reaction temperature of 120 ℃ in example 1 was added as control). As can be seen from the figure, the current density of the sample with the reaction temperature of 120 ℃ reaches 97.6mA cm under the potential of-1.3V^-2Sample (39.1 mA. cm) at a reaction temperature of 80 ℃ or higher^-2) And a sample (56.5 mA. cm) having a reaction temperature of 160 ℃^-2). Shows that the synthetic K is doped with Cu₂The reaction temperature of the Se nanostructure material significantly affects the electrocatalytic carbon dioxide reduction (CO)₂ER) activity, the reaction temperature is 120 ℃ and the active sites of the sample are the most, and the electrocatalytic carbon dioxide reduction reaction (CO)₂ER) activity was superior to samples with reaction temperatures of 80 ℃ and 160 ℃.

Example 6

soaking a piece of foamy Copper (CF) with the area of 2 x 3cm in 6M hydrochloric acid for 15min, and then washing with deionized water and absolute ethyl alcohol for 3 times respectively for later use; accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of SeO₂，1.5mmol NaBH₄150mmol NaOH and 0.2mmol KBr are added into the small beaker, stirred for 30min to obtain a uniform wine red solution, the solution is transferred into a stainless steel reaction kettle with a lining of 50mL polytetrafluoroethylene, the pretreated foamy copper is obliquely placed into the stainless steel reaction kettle, and the reaction is carried out in a drying oven at 120 ℃ for 6 h. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. K-doped Cu with a transverse average size of 1 μm is obtained₂Se nanosheet array structure material.

FIG. 24 is a SeO₂K-doped Cu for selenium source preparation₂Scanning Electron Microscope (SEM) images of Se nanosheet array structure materials. The sample is shown to be an interconnected nanosheet array structure with a large size.

FIG. 25 is a SeO₂K-doped Cu for selenium source preparation₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) The LSV polarization curve of (1) a sample prepared with Se powder as a selenium source was added as a control. As can be seen from the figure, the current density of the sample with Se powder as the selenium source reaches 97.6mA cm under the potential of-1.3V^-2Much higher than the selenium source is SeO₂Sample (23.3 mA. cm)^-2). Shows that the synthetic K is doped with Cu₂Se source of Se nanosheet array structure material has significant influence on electrocatalytic carbon dioxide reduction reaction (CO)₂ER), the active site of the sample with Se powder as the selenium source is more than that of the sample with SeO as the selenium source₂Sample of (2), electrocatalytic carbon dioxide reduction reaction (CO)₂ER) is SeO as an active ingredient superior to selenium source₂The sample of (1).

Example 7

accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH₄20mmol or 280mmol NaOH and 0.2mmol KBr are added into the small beaker, stirred for 30min to obtain wine red uniform solution, the solution is transferred into a stainless steel reaction kettle with 50mL polytetrafluoroethylene as an inner lining, the pretreated foamy copper is obliquely put into the solution and reacts for 6h in a 120 ℃ oven. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the addition amount of NaOH is 20mmol, the K-doped Cu with the coexisting small nano-sheets and nano-particles is obtained₂A Se nanostructure material; when the addition amount of NaOH is 280mmol, spherical K-doped Cu consisting of nanosheets is obtained₂A Se nanostructure material.

FIG. 26 shows K-doped Cu with NaOH added in 20mmol₂Scanning Electron Microscope (SEM) images of Se nanostructured materials. Indicating that the sample is a nanostructured material with small nanoplatelets and nanoparticles coexisting.

FIG. 27 shows the addition of 280mmol of NaOH in K-doped Cu₂Scanning Electron Microscope (SEM) images of Se nanostructured materials. The sample is shown to be a spherical structure consisting of the nano-sheets, and the transverse average size of the nano-sheets is 500 nm.

FIG. 28 shows the addition of NaOH in amounts of 20mmol and 280mmol of K-doped Cu₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) LSV polarization curve (LSV curve of sample prepared with 150mmol of example 1NaOH added as control). As can be seen from the figure, the current density of the sample with 150mmol of NaOH at-1.3V reached 97.6mA cm^-2Much higher than the sample (23.2mA cm) containing 20mmol of NaOH^-2) And a sample (54.0 mA. cm) containing NaOH in an amount of 280mmol^-2). Shows that the addition of NaOH significantly affects the synthesized K-doped Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nano-structured material₂ER), the maximum amount of active sites of a sample with 150mmol of NaOH added, electrocatalytic carbon dioxide reduction (CO)₂ER) was superior to samples with NaOH additions of 20mmol and 280 mmol.

Example 8

K-doped Cu₂The preparation method of the Se nano-structure material comprises the following steps:

accurately weighing 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 0.2mmol or 2.8mmol of NaBH₄150mmol NaOH and 0.2mmol KBr are added into the small beaker, stirred for 30min to obtain wine red uniform solution, the solution is transferred into a stainless steel reaction kettle with 50mL polytetrafluoroethylene as a lining, the pretreated foamy copper is obliquely put into the solution, and the reaction is carried out in a 120 ℃ oven for 6 h. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. NaBH₄When the addition amount of (2) is 0.2mmol, K-doped Cu with nanoparticles attached to the nano-sheets is obtained₂A Se nanostructure material; NaBH₄When the adding amount of (2.8) mmol, the nano flaky K doped Cu with larger size is obtained₂A Se nanostructure material.

FIG. 29 is NaBH₄K-doped Cu in an amount of 0.2mmol₂Scanning Electron Microscope (SEM) images of Se nanostructured materials. Indicating that the sample is a nano-structure material with nano-particles attached on a nano-sheet。

FIG. 30 is NaBH₄K-doped Cu in an amount of 2.8mmol₂Scanning Electron Microscope (SEM) images of Se nanostructured materials. The sample is shown to be a nano flaky structure material with a larger size, and the transverse average size of the nano sheet is 1.3 mu m.

FIG. 31 is NaBH₄K-doped Cu is added in an amount of 0.2mmol and 2.8mmol₂Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials₂ER) LSV polarization curve (example 1NaBH added to the figure)₄LSV curve of sample prepared with 1.5mmol addition as control). As can be seen, NaBH₄The current density of the sample with the addition amount of 1.5mmol reaches 97.6mA cm under the potential of-1.3V^-2Higher than NaBH₄A sample (21.4 mA. cm) was added in an amount of 0.2mmol^-2) And NaBH₄The amount of the sample (3) added was 2.8mmol (63.8 mA. cm)^-2). Indicating NaBH₄The addition of (A) significantly affects the synthesized K-doped Cu₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nano-structured material₂ER), NaBH₄Adding 1.5mmol of sample with most active sites, and electrocatalytic carbon dioxide reduction (CO)₂ER) activity superior to NaBH₄Samples were added in amounts of 0.2mmol and 2.8 mmol.

Example 9

accurately measuring 30mL of deionized water, adding into a clean small beaker, and accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH₄150mmol NaOH, 0.2mmol KCl or 0.2mmol KHCO₃Adding into the above small beaker, stirring for 30min to obtain wine red uniform solution, transferring the solution into 50mL stainless steel reaction kettle with polytetrafluoroethylene lining, placing pretreated foam copper into the solution, and reacting in oven at 120 deg.C for 6 h. And naturally cooling to room temperature after the reaction is finished, respectively washing the foam copper covered by the black sample for 3 times by using deionized water and absolute ethyl alcohol, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the potassium source is KCl, a thicker and smaller nanosheet array structure material is obtained; the potassium source is KHCO₃And obtaining the nano-sheet array structure material with nonuniform size.

FIG. 32K doped Cu prepared with KCl as potassium source₂Scanning Electron Microscope (SEM) images of Se nanosheet array structures. The sample is shown to be an array structure material composed of thicker and smaller nanosheets. The nanosheets had a transverse average size of 210 nm.

FIG. 33 is KHCO₃K-doped Cu prepared for potassium source₂Scanning Electron Microscope (SEM) images of Se nanosheet array structure materials. The sample is shown to be an array structure material consisting of nano sheets with nonuniform sizes, and the transverse average size of the nano sheets is 300 nm.

FIG. 34 is KCl or KHCO₃K-doped Cu prepared for potassium source₂Electrocatalytic carbon dioxide reduction (CO) reaction of Se nanosheet array structure material₂ER) LSV polarization curve (LSV curve of the sample prepared in example 1 with KBr as potassium source added as control). As can be seen from the figure, the current density of the sample with KBr as the potassium source reaches 97.6mA cm under the potential of-1.3V^-2Sample KCl higher than potassium source (71.2 mA. cm)^-2) And the potassium source is KHCO₃Sample (67.5 mA. cm)^-2). Shows that the synthetic K is doped with Cu₂The potassium source of the Se nanosheet array structure material obviously influences the electrocatalytic carbon dioxide reduction reaction (CO)₂ER) activity, most active sites of samples with KBr as potassium source, electrocatalytic carbon dioxide reduction (CO)₂ER) is KCl and KHCO which are better in activity than potassium source₃The sample of (1).

The above reference example is for a K-doped Cu₂The detailed description of the Se nanosheet array structure material, its method of preparation and use, is illustrative rather than limiting and several examples can be cited within the scope defined, thus changes and modifications that do not depart from the general concept of the present invention are intended to be within the scope of the present invention.

Claims

1. A preparation method of a K-doped cuprous selenide nanosheet array structure material is characterized by comprising the following steps:

obliquely placing the foamy copper in a mixed solution containing a selenium source, an alkali source, a reducing agent and an alkali metal salt, and carrying out hydrothermal reaction in a reaction kettle to prepare the K-doped cuprous selenide nanosheet array structure material.

2. The method according to claim 1, wherein the ratio of the amounts of the selenium source and the alkali metal salt is 3: 1-3.

3. The production method according to claim 1 or 2, characterized in that the ratio of the amounts of the substances of the selenium source, the alkali source, the reducing agent is: 3:500-2500:5-25.

4. The production method according to claim 1 or 2, wherein the selenium source is selenium powder.

5. The production method according to claim 1 or 2, characterized in that the alkali source is sodium hydroxide.

6. The production method according to claim 1 or 2, characterized in that the reducing agent is sodium borohydride.

7. The method according to claim 1 or 2, wherein the alkali metal is a potassium salt.

8. The method as claimed in claim 1 or 2, wherein the hydrothermal reaction is carried out at 100-140 ℃ for 5-7 h.

9. The K-doped cuprous selenide nanosheet array structure material prepared by the preparation method of any one of claims 1-8, wherein the morphology is a nanosheet array with the transverse dimension of 300-1300 nm.

10. The application of the K-doped cuprous selenide nanosheet array structure material disclosed by claim 9, which is used as an electrocatalyst for an electrocatalytic carbon dioxide reduction reaction.