CN114408877B - K-doped cuprous selenide nanosheet array structure material, preparation method and application thereof - Google Patents

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

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CN114408877B
CN114408877B CN202210100667.3A CN202210100667A CN114408877B CN 114408877 B CN114408877 B CN 114408877B CN 202210100667 A CN202210100667 A CN 202210100667A CN 114408877 B CN114408877 B CN 114408877B
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CN114408877A (en
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吴正翠
丁连春
高峰
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Anhui Normal University
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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 copper foam in mixed solution containing selenium source, alkali source, reducing agent and alkali metal saltAnd (3) carrying out hydrothermal reaction in the liquid in a reaction kettle to obtain the catalyst. The invention uses K + Ion doping into Cu 2 The Se nano sheet can effectively regulate the electron migration between atoms, K transfers electrons to Se to generate Se sites rich in electrons, and the nano sheet is linear * CO( * CO L ) And bridge type * CO( * CO B ) The intermediate has strong adsorption effect and promotes C-C coupling formation * COCHO intermediates significantly enhanced electrocatalytic carbon dioxide reduction (CO 2 ER) catalytic activity to ethanol. Simultaneously doping K + The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. In addition, dope K + The ions increase the conductivity of the catalyst and increase the transfer rate of interfacial 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 electrocatalytic cross application, and particularly relates to a K-doped cuprous selenide nano sheet array structure material, a preparation method and application thereof.
Background
Electrocatalytic carbon dioxide reduction provides a sustainable approach to reducing greenhouse gas emissions. In CO 2 C in the electro-reduction product 2+ Due to its ratio C 1 The products have a higher energy density and a higher value and are of great interest. Ethanol as CO 2 Electroreduced liquid C 2 The product is convenient to store and transport, and is widely used as a raw material for producing solvents, organic chemicals and disinfectants. However, ethanol production and other C's are due to the difficulty of C-C coupling 2+ Competing products, currently capable of high activity and selectivity of electrocatalytic CO 2 There is still little catalyst for the reduction to ethanol product. Thus, the development of highly active, selective and stable CO 2 The selective driving of the C-C coupling by the electro-reduction catalyst is critical to the formation of ethanol.
Copper is known to be the only source of C 2+ Single metal catalyst of the product. However, the overpotential of metallic copper is high, the variety of products is large, C 2+ The selectivity of the product is low. Furthermore, copper-based materials have a lower energy barrier and higher reaction kinetics for Hydrogen Evolution Reactions (HERs), whereas C 2+ The products are generally produced in a more negative potential range, which will be unavoidableAvoiding more hydrogen evolution side reactions. Different nanostructures of copper chalcogenides have been applied to CO 2 In the electroreduction, the S or Se element in the composition can improve the catalytic activity, but is mostly limited to C 1 The product is obtained.
Cuprous selenide (Cu) 2 Se) the catalyst has the advantages of complex preparation method, high preparation cost, low activity, poor selectivity, poor stability and the like when being used for electrocatalytic carbon dioxide reduction, and still limits the development and application of electrocatalytic carbon dioxide reduction.
Disclosure of Invention
The invention aims to provide a K-doped cuprous selenide nano-sheet array structure material and a preparation method thereof, wherein K-doped Cu taking foamy copper as a conductive substrate is prepared through one-step liquid phase reaction 2 Se nanometer sheet array structure material.
The invention also aims to provide the application of the K-doped cuprous selenide nano-sheet array structure material for electrocatalytic CO 2 And (3) reduction reaction. The material prepared by the invention, cu 2 The exposed (220) crystal face of the Se nano sheet is beneficial to * Adsorption of CO intermediates. K (K) + Ion doping into Cu 2 Cu 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 electrocatalytic CO is quickened 2 Conversion to ethanol, enhanced catalyst electrocatalytic CO 2 Activity, 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 specifically comprises the following steps:
and (3) obliquely placing the foam copper into a mixed solution containing a selenium source, an alkali source, a reducing agent and potassium salt, and performing hydrothermal reaction in a reaction kettle to obtain the K-doped cuprous selenide nanosheet array structure material.
The preparation method of the mixed solution containing selenium source, alkali source, reducing agent and potassium salt comprises the following steps: dissolving selenium source, alkali source, reducer and potassium salt in water, stirring to obtain mixed solution.
The water is preferably deionized water, and the volume is 20-35mL.
The ratio of the amounts of selenium source and potassium salt is 3:1-3, preferably 3:2.
The ratio of the amounts of substances of the selenium source, the alkali source and the reducing agent is as follows: 3:500-2500:5-25.
The alkali source is added in an amount of 50 to 250mmol, preferably 150mmol.
The reducing agent is added in an amount of 0.5 to 2.5mmol, preferably 1.5mmol.
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 condition is that the reaction is carried out for 5-7 hours at 100-140 ℃, preferably for 6 hours at 120 ℃.
The foam copper is required to be cleaned before being used, and the specific cleaning method comprises the following steps: firstly, soaking the substrate in 6M hydrochloric acid for 15min to remove an oxide film on the surface layer, then washing the substrate with deionized water and absolute ethyl alcohol, and cutting the substrate into a size of 2X 3cm when in use.
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, naturally cooling to room temperature, washing and drying to obtain the catalyst.
The washing is as follows: washing with deionized water for 3-5 times, and washing with absolute ethanol for 3-5 times.
The drying is as follows: drying in a vacuum drying oven at 60 ℃ for 12 hours.
In the preparation process, the foam copper is obliquely placed, so that the sample can uniformly grow on two sides of the foam copper.
The invention provides a K-doped cuprous selenide nano-sheet array structure material, which is prepared from K-doped Cu 2 The appearance of the Se nano sheet array structure material is a nano sheet array with the transverse dimension of 300-1300 nm.
The invention provides an application of a K-doped cuprous selenide nano-sheet array structure material as a material for electrocatalytic carbon dioxide reduction reaction (CO 2 ER) electrocatalyst.
The K-doped cuprous selenide nanosheet array structure material is used as an electrocatalytic carbon dioxide reduction reaction (CO) 2 ER) electrocatalyst, the specific application method is: cutting the K-doped cuprous selenide nanosheet array structure material into 0.5X0.5 cm size to serve as a working electrode, respectively using a carbon rod and an Ag/AgCl electrode as a counter electrode and a reference electrode, wherein electrolyte is 0.1M KHCO 3 The solution was electrochemically tested in a double electrode cell using a CHI 760E electrochemical workstation; by saturation of CO 2 0.1M KHCO of (2) 3 Faraday efficiency test of ethanol under different voltages and LSV polarization curve in electrolyte 2 ER performance. In contrast, 0.1M KHCO saturated with Ar was studied 3 K-doped Cu in electrolyte 2 LSV polarization curve of Se nano sheet array structure material. Linear scanning polarization curve (LSV) at 5.0 mV.s -1 Is performed at a scanning rate of (2). Stability was obtained by measuring the current density time curve at constant voltage. Electrochemically active area (ECSA) was measured by measuring the surface area of the substrate in the absence of distinct Faraday regions and at different scan rates (6, 7,8,9, 10, 11 and 12 mV.s -1 ) Electrochemical double layer capacitance (C) using cyclic voltammetry dl ) Evaluation was performed with a test voltage ranging from-0.08 to 0.02V (relative to the reversible hydrogen electrode); electrochemical Impedance (EIS) was tested at a frequency range of 100kHz to 0.01Hz and at-0.2V (relative to the reversible hydrogen electrode).
The inventors have found that the addition of alkali metal cations to the electrolyte can adsorb on the Cu electrode surface due to * The interaction of the CO intermediate and a local electric field generated by alkali metal cations in an electrochemical double layer is obviously promoted * CO adsorbs and increases the coverage of the catalyst surface. The inventors have explored the way to dope alkali metal cations into the lattice of Cu chalcogenides, adjust the electronic structure and active sites of the catalyst, optimize * Adsorption of the CO intermediate and other ethanol intermediates on the catalyst surface effectively produces ethanol products.There is no report in the prior art of doping alkali metal cations into Cu chalcogenide lattices for electrocatalytic carbon dioxide reduction.
In the preparation method of the invention, the copper on the surface of the foamy copper is dissolved in O in the solution by a simple one-step chemical liquid phase synthesis method 2 Oxidation to form Cu 2+ Ion and OH in solution - Bonding to form Cu (OH) 2 Further conversion to Cu (OH) in the presence of excess base (NaOH) 4 2- Ions are then gradually taken up by BH in solution 4 - Ion reduction to form Cu + Ions. Selenium powder is dissolved in solution BH under strong alkaline (NaOH) condition 4 - Ion rapid reduction to Se 2 2- Ions, and further over-heated with BH 4 - Ion reduction to Se 2- Ions. Cu (Cu) + Ions and Se 2- Ion reaction to form cubic Cu 2 Se seed crystal. Planar quadrilateral Cu (OH) present in solution 4 2- Adsorbed on Cu 2 The (220) surface of Se seed crystal induces the seed crystal to grow into cuprous selenide nano-sheets with exposed (220) crystal face gradually in an oriented way, and simultaneously K in the solution + Ion doping to Cu 2 In the crystal lattice of Se, the K-doped cuprous selenide nano-sheet array structure material growing on the foam copper is formed.
In the invention, K is doped with Cu 2 The Se nano sheet optimizes the electronic structure of the catalyst and adjusts the electronic interaction between atoms. By transferring electrons to Se through K, se sites rich in electrons are generated, and CO is electrostatically adsorbed 2 Molecules form Se-C bonds, promoting linear CO 2 Conversion to a bend adsorbed at Se sites * CO 2 – An intermediate. Further reduced to positively charged wires adsorbed on Se sites by a proton-coupled electron transfer (PCET) step * CO L Intermediate and negatively charged bridge adsorbed at Cu sites * CO B An intermediate. * CO B Further reduction of the intermediate to form * CHO intermediate, with * CO L Intermediate coupling to adsorb at Cu sites * COCHO intermediates via multi-step protonsAfter the step of transferring the coupled electrons, * conversion of COCHO intermediate to O-terminal adsorption at Cu site * OCH 2 CH 3 Intermediate, finally ethanol (C) is produced by protonation 2 H 5 OH)。K + Ion doping enhances the wire-type * CO L Intermediate and bridge * CO B The adsorption strength of the intermediate can better protect Cu in the electrocatalytic process 2 Cu in Se + Species, prolong the retention time of the carbon-containing intermediate on the surface of the catalyst, promote the formation of C-C coupling * COCHO intermediates for enhanced electrocatalytic CO 2 Catalytic activity for reduction to ethanol. Simultaneously doping K + The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. In addition, K + Ion doping improves the conductivity of the catalyst and significantly increases the transfer rate of interfacial charges. Thus the material was used in potassium bicarbonate (KHCO 3 ) Electrocatalytic CO in electrolyte 2 The reduction to ethanol shows excellent activity, selectivity and stability, and can be used for electrocatalytic CO 2 The practical application of reduction to ethanol is very valuable. The invention provides an electrocatalytic carbon dioxide reduction reaction (CO 2 ER) has the characteristics of low overpotential for producing ethanol products, high selectivity, good stability, simple preparation process, environmental protection and low cost.
Drawings
FIG. 1 is a K-doped Cu prepared in example 1 2 X-ray powder diffraction (XRD) pattern of Se nanoplatelet array structure materials;
FIG. 2 is a K-doped Cu prepared in example 1 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 3 is a K-doped Cu prepared in example 1 2 Energy dispersive X-ray (EDX) spectroscopy of Se nanoplatelet array structural materials;
FIG. 4 is a K-doped Cu prepared in example 1 2 Transmission Electron Microscope (TEM) images of Se nanoplatelet array structure materials;
FIG. 5 is a K-doped Cu prepared in example 1 2 High Se nano sheet array structure materialResolving a lattice fringe (HRTEM) pattern;
FIG. 6 is a K-doped Cu prepared in example 1 2 Raman spectrum (Raman) diagram of Se nanoplatelet array structure material;
FIG. 7 is a graph of the K-doped Cu prepared in example 2 with a K-doped mass percent of 5.9% and 15.9% 2 An energy dispersive X-ray spectroscopy (EDX) map of the Se nanoplatelet array structure material;
FIG. 8 is a graph of K-doped Cu with a mass percent of 5.9% for the K-doped alloy of example 2 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 9 is a graph of 15.9% K-doped Cu by mass percent K-doped prepared in example 2 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 10 shows K-doped Cu with different K contents (5.9%, 11.2% and 15.9%) prepared in example 1 and example 2 2 Se and undoped Cu prepared in example 3 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure 2 ER) LSV curve;
FIG. 11 is a K-doped Cu prepared in example 1 and example 3 2 Se nanoplatelets and undoped Cu 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) faraday efficiency plot of the product;
FIG. 12 is a K-doped Cu prepared in example 2 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) faraday efficiency plot of the product;
FIG. 13 is a diagram of K-doped Cu in example 1 2 Se nano sheet array structural material electrocatalytic carbon dioxide reduction reaction (CO) 2 ER) current density time plot;
FIG. 14 is a graph showing the K-doped Cu of example 1 and example 2 2 Se nano sheet array structural material and undoped Cu in example 3 2 Se nano sheet array structural material electrocatalytic carbon dioxide reduction reaction (CO) 2 ER) capacitance current plot;
FIG. 15 shows K-doped Cu in example 1 and example 2 2 Se nanosheet array structure material and example 3Not doped with Cu 2 Se nano sheet array structural material electrocatalytic carbon dioxide reduction reaction (CO) 2 ER);
FIG. 16 is a graph showing the K-doped Cu of example 1 2 Se nano-sheet array structural material is used for electrocatalytic carbon dioxide reduction reaction (CO) under potential of-0.8V 2 ER) in situ infrared spectra over time;
FIG. 17 is a graph of K-doped Cu prepared in example 4 with a reaction time of 4h 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 18 is a graph of K-doped Cu prepared in example 4 with a reaction time of 8h 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 19 is a graph of K-doped Cu prepared in example 4 with reaction times of 4h and 8h 2 X-ray powder diffraction (XRD) pattern of Se nanoplatelet array structure materials;
FIG. 20 shows the preparation of example 4 with a reaction time of 4h or 8h for K-doped Cu 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) (LSV curve of sample prepared with reaction time of 6h of example 1 was added as control).
FIG. 21 is a graph of K-doped Cu prepared in example 5 and having a reaction temperature of 80 ℃ 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 22 shows the preparation of example 5 with a reaction temperature of 160℃for K-doped Cu 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 23 shows the preparation of example 5 with K-doped Cu having a reaction temperature of 80℃or 160 ℃ 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) (LSV curve of sample prepared with reaction temperature of 120 ℃ in example 1 added as control);
FIG. 24 is a sample of SeO prepared in example 6 2 K-doped Cu for selenium source 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 25 shows the preparation of SeO according to example 6 2 K-doped Cu for selenium source 2 Se nanometerElectrocatalytic carbon dioxide reduction (CO) of sheet array structural materials 2 ER) (LSV curve of sample prepared with Se powder as selenium source of example 1 added as control in the figure);
FIG. 26 is a graph of K-doped Cu with NaOH of 20mmol in example 7 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 27 is a graph of K-doped Cu with NaOH of 280mmol in the preparation of example 7 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 28 is a graph of K-doped Cu with NaOH of 20mmol or 280mmol as prepared in example 7 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) (LSV curve of sample prepared with 150mmol NaOH addition of example 1 as control);
FIG. 29 is a NaBH of example 8 4 K-doped Cu with addition of 0.2mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 30 is a NaBH of example 8 4 K-doped Cu with addition of 2.8mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials;
FIG. 31 is a NaBH of example 8 4 K-doped Cu with addition amount of 0.2mmol or 2.8mmol 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) (shown in the figure, example 1NaBH is added 4 LSV curve of 1.5mmol of prepared sample was used as control);
FIG. 32 is a K-doped Cu with KCl as the potassium source prepared in example 9 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 33 shows that the potassium source prepared in example 9 is KHCO 3 K-doped Cu of (2) 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials;
FIG. 34 shows the potassium source KCl or KHCO prepared in example 9 3 K-doped Cu of (2) 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) (in the figure, example 1 was added as KBr)LSV curve of samples prepared for potassium source as control).
Detailed Description
The invention will now be described in detail with reference to the examples and the accompanying drawings.
Example 1
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
soaking a piece of foam Copper (CF) with the area of 2X 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 weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 150mmol NaOH,0.2mmol KBr adding into the small beaker to form a mixed solution, stirring for 30min to obtain a uniform wine red solution, transferring the solution into a 50mL stainless steel reaction kettle with polytetrafluoroethylene as a lining, obliquely placing the pretreated foamy copper into the stainless steel reaction kettle, and reacting for 6h in a baking oven at 120 ℃. Naturally cooling to room temperature after the reaction is finished, cleaning the black sample covered copper foam with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours to obtain K-doped Cu 2 Se nanometer sheet array structure material.
Characterization of structure and morphology of the product:
the final product obtained in example 1 was phase identified by X-ray powder diffractometer (XRD). As shown in FIG. 1, all diffraction peaks are equal to cubic Cu 2 Se (JCPDS No. 65-2982) are matched.
The product obtained in example 1 was subjected to morphological analysis by means of a Scanning Electron Microscope (SEM). As shown in fig. 2, the sample has a uniformly distributed nano-sheet array structure, and the transverse dimension of the nano-sheet is 300-400nm.
The final product composition of example 1 was analyzed using energy dispersive X-ray (EDX) spectroscopy. As shown in fig. 3, the atomic percentages of 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％ -Cu 2 Se。
The product of example 1 was subjected to morphological analysis using a Transmission Electron Microscope (TEM). As shown in fig. 4, the sample is a flexible nanoplatelet 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 Cu 2 The (220) crystal plane of Se.
The vibrational modes of the product obtained in example 1 were characterized by raman spectroscopy. As shown in FIG. 6, the Raman spectrum is 271 cm -1 A peak appears at the position corresponding to Cu 2 Cu-Se vibration of Se.
Example 2
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
accurately weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 150mmol NaOH,0.1mmol or 0.3mmol KBr is added into the small beaker, the mixture is stirred for 30min to obtain a wine red uniform solution, the solution is transferred into a 50mL stainless steel reaction kettle with polytetrafluoroethylene as a lining, copper foam is treated according to the method of example 1, the pretreated copper foam is obliquely placed into the solution, and the solution is reacted in an oven at 120 ℃ for 6h. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When KBr was added in an amount of 0.1mmol, K-doped Cu having a K doping amount of 5.9% was obtained 2 Se nano sheet array structure material; when KBr was added in an amount of 0.3mmol, K-doped Cu having a K doping amount of 15.9% was obtained 2 Se nanometer sheet 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 are 30.20:16.32:5.44 and 24.37:11.50:11.47, respectively, and the mass percentages of K elements are calculated to be 5.9% and 15.9%, respectively. The product of this example 2 is written as K 5.9％ -Cu 2 Se and K 15.9％ -Cu 2 Se。
Further examples using Scanning Electron Microscopy (SEM)2 morphology of the sample was analyzed. FIGS. 8 and 9 are K, respectively 5.9％ -Cu 2 Se nanosheet array and K 15.9％ -Cu 2 SEM image of Se nano sheet array shows that the sample is an array structure composed of interconnected nano sheets. Wherein the transverse average size of the nanoplatelets was 300nm at a K doping level of 5.9% (fig. 8). The lateral average size of the nanoplatelets was 410nm at 15.9% K doping (FIG. 9).
Example 3
K doped Cu 2 Se nano sheet array structure material as electrocatalytic carbon dioxide reduction reaction (CO) 2 ER) catalyst.
The specific application method comprises the following steps: cu was doped with K having an area of 0.5X0.5 cm 2 Se nano sheet 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 KHCO is carried out at 0.1M 3 Electrochemical testing was performed in the electrolyte using a CHI 760E electrochemical workstation at room temperature (25 ℃); by Linear Sweep Voltammetry (LSV) at 5.0mV s -1 Obtaining a polarization curve from the scan rate of (a); by saturation of CO 2 0.1M KHCO of (2) 3 Faraday efficiency test of ethanol under different voltages and LSV polarization curve in electrolyte 2 ER performance.
Under the same conditions as above, with Cu 2 The Se nano sheet is used as a working electrode for testing and is used as a comparison experiment. Wherein Cu is 2 The Se nanoflakes were prepared on the basis of example 1, omitting KBr from the starting materials, defined as Cu 2 Se。
FIG. 10 shows K-doped Cu with K doping amounts of 5.9%,11.2% and 15.9% prepared in example 1, example 2 and example 3 2 Se and undoped Cu 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) LSV polarization curve. From the figure, K 11.2％ -Cu 2 Se nano sheet array structure material has current density of 97. mA cm under-1.3V potential -2 Higher than K 5.9％ -Cu 2 Se(76.1mA·cm -2 )，K 15.9％ -Cu 2 Se(83.2mA·cm -2 ) And undopedCu 2 Se (66.2mA·cm -2 ) The method comprises the steps of carrying out a first treatment on the surface of the Indicating that K is doped with Cu 2 Sample activity of Se is superior to undoped Cu 2 The mass percent of Se and K doping significantly affects the electrocatalytic carbon dioxide reduction reaction (CO 2 ER) activity, the sample activity with the K doping mass percentage of 11.2% is better than the samples with the doping amounts of 5.9% and 15.9%.
FIG. 11 is K 11.2％ -Cu 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) product, giving by comparison undoped Cu 2 Se for CO 2 Faraday efficiency plot of ER product. K (K) 11.2％ -Cu 2 The Faraday efficiency of the Se nano sheet array structure material for producing ethanol under the potential of-0.8V can reach 70.3 percent, which is far higher than that of undoped Cu 2 12.1% of Se. FIG. 12 is K 5.9％ -Cu 2 Se and K 15.9％ -Cu 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) faraday efficiency plot of the product. K (K) 5.9％ -Cu 2 The Faraday efficiency of the Se nano sheet array structure material for generating ethanol under the potential of-0.8V is maximum and is 27.6%. K (K) 15.9％ -Cu 2 The Faraday efficiency of the Se nano sheet array structure material for generating ethanol under the potential of-0.9V is maximum and is 46.0%.
FIG. 13 is K 11.2％ -Cu 2 Se nano-sheet array structural material evaluates electrocatalytic carbon dioxide reduction reaction (CO) under-0.8V potential 2 ER) stability of the current density versus time curve. After 12h of testing, the current density remained above 97% of the initial value, indicating K 11.2％ -Cu 2 Se nano sheet array structure material has excellent electrocatalytic carbon dioxide reduction reaction (CO) 2 ER).
FIG. 14 shows the electrocatalytic carbon dioxide reduction reaction (CO) at different sweep rates 2 ER). K (K) 11.2％ -Cu 2 The double-layer capacitance of the Se nano sheet array structure material is 37.1 mF.cm -2 Greater than Cu 2 20.7 mF.cm of Se -2 ，K 5.9％ -Cu 2 24.4 mF.cm of Se -2 And K 15.9％ -Cu 2 Se 27.1 mF.cm -2 . Thus, the electrocatalytic carbon dioxide reduction reaction (CO) of the material can be increased after K doping 2 ER), a moderate doping amount of K 11.2％ -Cu 2 The Se nano sheet array structure material has the largest electrochemical active area.
FIG. 15 shows an electrocatalytic carbon dioxide reduction reaction (CO 2 ER) Electrochemical Impedance (EIS) plot under conditions. The semicircle diameters of the samples after K doping are all larger than those of undoped Cu 2 Se is small, wherein K 11.2％ -Cu 2 The semi-circle diameter of the Se sample is minimum, which shows that the resistance of the catalyst can be obviously reduced after K doping, and the catalytic dynamics of the electrocatalytic carbon dioxide reduction reaction can be accelerated.
FIG. 16 is K 11.2％ -Cu 2 Se nano-sheet array structural material is used for electrocatalytic carbon dioxide reduction reaction (CO) under potential of-0.8V 2 ER) was varied over time (measured every 2min until no intermediate was varied at 14 min. To investigate the retention time of the intermediates, an in situ infrared spectrum of 2h was again tested. ) In situ infrared spectrogram of (a). At the initial stage of the reaction, the bridge type is formed along with the extension of the reaction time * CO B Sum line type * CO L Intermediate to high wavenumber shift * OH intermediate to low wavenumber shift, illustrating bridge * CO B Sum line type * CO L Adsorption of the intermediate on the catalyst surface is enhanced * Adsorption of OH is reduced, thereby promoting electrocatalytic carbon dioxide reduction (CO 2 ER) and inhibits competing Hydrogen Evolution Reactions (HER). After 2 hours of electrolysis, K 11.2％ -Cu 2 All intermediates on Se remain unchanged, which means that K doping can lead the surface of the catalyst to retain carbon-containing intermediates for a long time, and is beneficial to C-C coupling to generate ethanol.
By the comparison, the invention can obtain K + Ion doping into Cu 2 The Se nano sheet can effectively regulate the electron migration between atoms, K transfers electrons to Se to generate Se sites rich in electrons, and the nano sheet is linear * CO( * CO L ) And bridge type * CO( * CO B ) The intermediate has strong adsorption effectPromoting C-C coupling formation * COCHO intermediates to enhance electrocatalytic carbon dioxide reduction (CO 2 ER) catalytic activity to ethanol. Simultaneously doping K + The ions can increase the electrochemically active area of the catalyst, exposing more catalytically active sites. In addition, dope K + The ions increase the conductivity of the catalyst and significantly increase the transfer rate of interfacial charges. The K-doped cuprous selenide (Cu 2 Se) nanosheet array structure material in potassium bicarbonate (KHCO) 3 ) Electrocatalytic carbon dioxide reduction (CO) in electrolyte 2 ER) 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) 2 ER) into ethanol.
Example 4
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
accurately weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 150mmol NaOH,0.2mmol KBr adding into the small beaker, stirring for 30min to obtain a wine red uniform solution, transferring the solution into a 50mL stainless steel reaction kettle with polytetrafluoroethylene as a lining, treating the foam copper according to the method of example 1, obliquely placing the pretreated foam copper into the solution, and reacting for 4h or 8h in a 120 ℃ oven. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. When the reaction time is 4 hours, the K doped Cu in the film shape which is not fully grown into the nano-sheet is obtained 2 Se nanostructure material; obtaining K doped Cu with the transverse average size of 800nm when the reaction time is 8h 2 Se nanometer sheet array structure material.
FIG. 17 is a graph of K-doped Cu with a reaction time of 4h 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials. Indicating that the samples were interconnected, not fully grown, film-like nanostructures.
FIG. 18 is a graph of K doped C with a reaction time of 8hu 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials. Indicating that the sample is an array structure formed by interconnecting larger and thicker nano-sheets, and the average transverse dimension of the nano-sheets is 800 nm.
FIG. 19 is a graph of K-doped Cu with reaction times of 4h and 8h 2 X-ray powder diffraction (XRD) pattern of Se nanostructure material. When the reaction time was 4 hours, the reaction time was not Cu 2 The precursor Cu (OH) appears besides the diffraction peak of Se 2 The diffraction peak of (2) shows incomplete reaction and incomplete conversion to Cu at a reaction time of 4 hours 2 Se. When the reaction time is 8 hours, only Cu 2 Diffraction peaks of Se.
FIG. 20 is a graph of K-doped Cu with reaction times of 4h and 8h 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanoplatelet array materials 2 ER) polarization curve (LSV curve of sample prepared with reaction time of 6h of example 1 was added as control). As is clear from the graph, the current density of the sample with the reaction time of 6h reaches 97.6mA.cm at the potential of-1.3V -2 Higher than the sample having a reaction time of 4 hours (34.5 mA.cm -2 ) And a sample (46.6 mA.cm) -2 ). Indicating that the synthesis of K-doped Cu 2 The reaction time of the Se nanoplatelet array material significantly affects the electrocatalytic carbon dioxide reduction reaction (CO 2 ER) activity, the most active sites of the sample with a reaction time of 6h, electrocatalytic carbon dioxide reduction (CO) 2 ER) activity was better than the samples with reaction times of 4h and 8h.
Example 5
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
soaking a piece of foam Copper (CF) with the area of 2X 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 weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 150mmol NaOH,0.2mmol KBr adding into the small beaker, stirring for 30min to obtain uniform wine red solution, transferring the solution into a stainless steel reaction kettle with 50mL polytetrafluoroethylene lining, and obliquely placing pretreated foamy copper into the stainless steel reaction kettleIn the reaction for 6h in an oven at 80 ℃ or 160 ℃. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. At the reaction temperature of 80 ℃, the K doped Cu in the form of a film composed of nano particles is obtained 2 Se nanostructure material; at a reaction temperature of 160 ℃, K-doped Cu with a transverse average size of 400nm is obtained 2 Se nanometer sheet array structure material.
FIG. 21 is a graph of K-doped Cu with a reaction temperature of 80 ℃ 2 Scanning Electron Microscope (SEM) images of Se nanostructures. Indicating that the sample is a thin film structure of nanoparticles.
FIG. 22 is a graph of K-doped Cu with a reaction temperature of 160 ℃ 2 Scanning Electron Microscope (SEM) images of Se nanostructures. The sample is an array structure formed by connecting thicker nano sheets, and the average transverse dimension of the nano sheets is 400nm.
FIG. 23 is a graph of K-doped Cu with reaction temperatures of 80℃and 160 ℃ 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) LSV polarization curve (LSV curve of sample prepared with reaction temperature of 120 ℃ in example 1 added as control). As is clear from the graph, the sample having a reaction temperature of 120℃had a current density of 97.6 mA.cm at a potential of-1.3V -2 A sample (39.1 mA.cm) -2 ) And a sample (56.5 mA.cm) -2 ). Indicating that the synthesis of K-doped Cu 2 The reaction temperature of Se nanostructured materials significantly affects the electrocatalytic carbon dioxide reduction reaction (CO 2 ER) activity, maximum active sites of the sample at 120 ℃ reaction temperature, electrocatalytic carbon dioxide reduction (CO) 2 ER) activity was superior to samples with reaction temperatures of 80 ℃ and 160 ℃.
Example 6
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
soaking a piece of foam Copper (CF) with the area of 2X 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 measure 30mL deionized waterAdding into a clean small beaker, accurately weighing 0.3mmol of SeO 2 ，1.5mmol NaBH 4 150mmol NaOH,0.2mmol KBr adding into the small beaker, stirring for 30min to obtain uniform wine red solution, transferring the solution into a stainless steel reaction kettle with 50mL polytetrafluoroethylene lining, obliquely placing the pretreated foamy copper into the stainless steel reaction kettle, and reacting for 6h in a baking oven at 120 ℃. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. Obtaining K-doped Cu with a transverse average size of 1 μm 2 Se nanometer sheet array structure material.
FIG. 24 is a diagram of SeO 2 K-doped Cu prepared for selenium source 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials. Indicating that the sample is in an interconnected nano-sheet array structure with larger size.
FIG. 25 shows SeO 2 K-doped Cu prepared for selenium source 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) (LSV curve of sample prepared with Se powder as selenium source of example 1 was added as control). As can be seen from the graph, the current density of the sample with Se powder as the Se source reaches 97.6mA.cm at the potential of-1.3V -2 Far higher than the selenium source is SeO 2 Is (23.3 mA.cm) -2 ). Indicating that the synthesis of K-doped Cu 2 The selenium source of the Se nano sheet array structure material significantly affects the electrocatalytic carbon dioxide reduction reaction (CO) 2 ER), the sample active site of Se powder is more than that of Se powder, and the Se source is SeO 2 Is a sample of an electrocatalytic carbon dioxide reduction reaction (CO 2 ER) activity superior to selenium source is SeO 2 Is a sample of (a).
Example 7
K doped Cu 2 The preparation method of the Se nano sheet array structure material comprises the following steps:
accurately weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 Adding 20mmol or 280mmol NaOH,0.2mmol KBr into the small beaker, stirring for 30min to obtain uniform wine redTransferring the solution into a stainless steel reaction kettle with 50mL polytetrafluoroethylene lining, obliquely placing the pretreated foam copper into the solution, and reacting for 6 hours in a baking oven at 120 ℃. And naturally cooling to room temperature after the reaction is finished, cleaning the copper foam covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12h. When the addition amount of NaOH is 20mmol, the K doped Cu with the coexistence of the small nano-sheets and nano-particles is obtained 2 Se nanostructure material; when the addition amount of NaOH is 280mmol, spherical K-doped Cu consisting of nano-sheets is obtained 2 Se nanostructure material.
FIG. 26 is a graph of K-doped Cu with NaOH at 20mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials. Indicating that the sample is a nanostructural material in which both small nanoplatelets and nanoparticles coexist.
FIG. 27 is a graph of K-doped Cu with NaOH at 280mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials. The sample is shown to be a spherical structure consisting of nano-sheets, and the transverse average size of the nano-sheets is 500nm.
FIG. 28 is a graph of K-doped Cu with NaOH additions of 20mmol and 280mmol 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) LSV polarization curve (LSV curve of sample prepared with 150mmol NaOH addition of example 1 was added as control). As is clear from the graph, the sample with 150mmol of NaOH added had a current density of 97.6mA.cm at a potential of-1.3V -2 Far higher than that of the sample (23.2 mA.cm) -2 ) And a sample (54.0mA.cm) -2 ). Indicating that the addition of NaOH significantly affects the synthesized K-doped Cu 2 Se nanostructured materials electrocatalytic carbon dioxide reduction reactions (CO 2 ER), the maximum active sites of the sample with NaOH addition of 150mmol, electrocatalytic carbon dioxide reduction (CO 2 ER) is superior to samples with NaOH additions of 20mmol and 280 mmol.
Example 8
K doped Cu 2 The preparation method of the Se nano structure material comprises the following steps:
accurately weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder, 0.2mmol or 2.8mmol of NaBH 4 150mmol NaOH,0.2mmol KBr adding into the small beaker, stirring for 30min to obtain a wine red uniform solution, transferring the solution into a stainless steel reaction kettle with 50mL polytetrafluoroethylene lining, obliquely placing the pretreated foamy copper into the solution, and reacting for 6h in a baking oven at 120 ℃. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, and drying the obtained sample in a vacuum drying oven at 60 ℃ for 12 hours. NaBH 4 When the addition amount of the (B) is 0.2mmol, K-doped Cu with nano particles attached to the nano sheet is obtained 2 Se nanostructure material; naBH 4 When the addition amount of the catalyst is 2.8mmol, the nano-sheet-shaped K-doped Cu with larger size is obtained 2 Se nanostructure material.
FIG. 29 is a NaBH 4 K-doped Cu with addition of 0.2mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials. Indicating that the sample is a nanostructured material with nanoparticles attached to the nanoplatelets.
FIG. 30 is a NaBH 4 K-doped Cu with addition of 2.8mmol 2 Scanning Electron Microscope (SEM) images of Se nanostructure materials. The sample is shown to be a nano-sheet structural material with larger size, and the transverse average size of the nano-sheet is 1.3 mu m.
FIG. 31 is a NaBH 4 K-doped Cu with addition amounts of 0.2mmol and 2.8mmol 2 Electrocatalytic carbon dioxide reduction (CO) of Se nanostructured materials 2 ER) LSV polarization curve (in the figure, example 1NaBH is added 4 LSV curve of 1.5mmol of prepared sample was added as a control). From the figure, naBH 4 The current density of the sample with the addition amount of 1.5mmol reaches 97.6mA.cm under the potential of-1.3V -2 Higher than NaBH 4 A sample (21.4 mA.cm) -2 ) And NaBH 4 Is added to a sample (63.8 mA.cm) -2 ). Indicating NaBH 4 Is added in an amount that significantly affects the synthesized K-doped Cu 2 Se nanostructured materials electrocatalytic carbon dioxide reduction reactions (CO 2 ER), naBH 4 The maximum amount of 1.5mmol of sample active site is added, and the electrocatalytic carbon dioxide reduction reaction (CO 2 ER) activity is superior to NaBH 4 Samples were added in amounts of 0.2mmol and 2.8 mmol.
Example 9
K doped Cu 2 The preparation method of the Se nano structure material comprises the following steps:
accurately weighing 30mL of deionized water, adding into a clean small beaker, accurately weighing 0.3mmol of Se powder and 1.5mmol of NaBH 4 150mmol NaOH,0.2mmol KCl or 0.2mmol KHCO 3 Adding the solution into the small beaker, stirring for 30min to obtain a wine red uniform solution, transferring the solution into a 50mL stainless steel reaction kettle with polytetrafluoroethylene as a lining, obliquely placing the pretreated foam copper into the solution, and reacting for 6h in a baking oven at 120 ℃. And naturally cooling to room temperature after the reaction is finished, cleaning the foam copper covered by the black sample with deionized water and absolute ethyl alcohol for 3 times, 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 nano-sheet array structure material is obtained; the potassium source is KHCO 3 And obtaining the nano-sheet array structural material with non-uniform size.
FIG. 32 is a K-doped Cu prepared with KCl as a potassium source 2 Scanning Electron Microscope (SEM) image of Se nanoplatelet array structure. Indicating that the sample is an array structure material composed of thicker and smaller nano-sheets. The lateral average size of the nanoplatelets was 210nm.
FIG. 33 shows KHCO 3 K-doped Cu prepared for potassium source 2 Scanning Electron Microscope (SEM) images of Se nanoplatelet array structure materials. The sample is an array structure material composed of nano sheets with nonuniform sizes, and the transverse average size of the nano sheets is 300nm.
FIG. 34 is a KCl or KHCO 3 K-doped Cu prepared for potassium source 2 Electrocatalytic carbon dioxide reduction reaction (CO) of Se nano sheet array structure material 2 ER) LSV polarization curve (LSV curve of sample prepared with KBr as potassium source of example 1 was added as control). As can be seen from the graph, the sample with KBr as the potassium source has a current density of 97.6mA.cm at a potential of-1.3V -2 Samples higher than KCl as potassium sourceProduct (71.2 mA cm) -2 ) And the potassium source is KHCO 3 Is (67.5 mA.cm) -2 ). Indicating that the synthesis of K-doped Cu 2 The potassium source of the Se nano sheet array structure material significantly affects the electrocatalytic carbon dioxide reduction reaction (CO) 2 ER) activity, the most active site of the sample with KBr as potassium source, electrocatalytic carbon dioxide reduction (CO) 2 ER) activity superior to potassium sources is KCl and KHCO 3 Is a sample of (a).
The above reference example is directed to a K-doped Cu 2 The detailed description of the Se nanosheet array structure material and the preparation method and application thereof is illustrative and not restrictive, and several embodiments can be listed according to the limited scope, so that the invention shall fall within the protection scope of the invention without departing from the general inventive concept.

Claims (5)

1. The preparation method of the K-doped cuprous selenide nanosheet array structure material is characterized by specifically comprising the following steps of:
obliquely placing the foamy copper into a mixed solution containing a selenium source, an alkali source, a reducing agent and alkali metal salt, and performing hydrothermal reaction in a reaction kettle to prepare a K-doped cuprous selenide nanosheet array structure material;
the alkali source is sodium hydroxide;
the reducing agent is sodium borohydride;
the alkali metal is potassium salt;
the ratio of the amounts of the selenium source and alkali metal salt is 3:1-3;
the ratio of the amounts of substances of the selenium source, the alkali source and the reducing agent is as follows: 3:500-2500:5-25.
2. The method of claim 1, wherein the selenium source is selenium powder.
3. The method according to claim 1, wherein the hydrothermal reaction is carried out at 100 to 140 ℃ under conditions of 5 to 7 h.
4. A K-doped cuprous selenide nanosheet array structure material prepared by the preparation method of any one of claims 1-3, wherein the morphology of the material is a nanosheet array with a transverse dimension of 300-1300 nm.
5. The use of the K-doped cuprous selenide nanosheet array structure material as claimed in claim 4 as an electrocatalyst for electrocatalytic carbon dioxide reduction reaction.
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