The invention content is as follows:
aiming at the defects of the prior art and the requirements of research and application in the field, one of the purposes of the invention is to provide a core-shell copper selenide @ nickel iron hydrotalcite-like electrocatalyst which is characterized in that the catalyst takes foam copper as a substrate, and Cu (OH) is grown on the surface of the catalyst in situ by a chemical oxidation method in an alkaline medium 2Selenizing the nano-wire by selenium powder in a tube furnace to be converted into a copper selenide nano-wire, and finally growing the nickel-iron hydrotalcite on the surface of the nano-wire by an electrodeposition method; the copper foam is CF, the copper selenide is Cu2Se, nickel-iron hydrotalcite is recorded as NiFe-LDH, and copper selenide @ nickel-iron hydrotalcite is recorded as Cu2Se@NiFe-LDH;
The second purpose of the invention is to provide a preparation method of the core-shell copper selenide @ ferronickel hydrotalcite electrocatalyst, which comprises the following steps:
(1)Cu2preparation of Se/CF
Soaking commercial foam copper with the specification of 3cm multiplied by 4cm in a hydrochloric acid solution with the concentration of 37% for 10 minutes, and washing for a plurality of times by using deionized water and absolute ethyl alcohol; the cleaned foamy copper is put into 80mL NaOH and (NH)4)2S2O8The mixed solution is soaked for 20min, so that light blue Cu (OH) grows on the surface in situ2Nanowire, taking out Cu (OH) grown thereon2Washing the foam copper of the nanowire with deionized water, and drying in an oven at 60 ℃ for 6 h; will be provided withDried Cu (OH)2Placing the nanowire in a tube furnace, simultaneously placing 0.1g selenium powder at the front end of the tube furnace, heating to 400 ℃ at a speed of 5 ℃/min in a nitrogen atmosphere, keeping for 30min, taking out a sample after the tube furnace is naturally cooled, and washing with deionized water and ethanol for several times to obtain Cu 2Se/CF, drying for later use;
(2)Cu2preparation of Se @ NiFe-LDH/CF
With Cu2Se/CF as working electrode, Pt wire electrode as counter electrode, saturated calomel electrode as reference electrode, and Ni (NO) as electrolyte3)2And FeSO4Electrifying the mixed aqueous solution for 60-150 s under the condition that the potential is-1.0V to perform an electrodeposition reaction so as to grow NiFe-LDH on the surface of the mixed aqueous solution, and preparing the nuclear shell Cu2Se @ NiFe-LDH/CF catalyst;
wherein NaOH and (NH) in step (1)4)2S2O8NaOH and (NH)4)2S2O8The molar concentrations of the compounds are respectively 2.5 and 0.125 mol/L; ni (NO) in step (2)3)2And FeSO4The total concentration of metal ions in the mixed aqueous solution is 0.15-0.45 mol/L, Ni (NO)3)2And FeSO41-6: 2.
the electrocatalyst prepared by the preparation method is in a nanowire shape, and the diameter of the electrocatalyst is 150-250 nm; with Cu2Se is taken as a core, NiFe-LDH sheets are taken as shells, and the thickness of the NiFe-LDH sheets is less than 10 nm.
Core-shell Cu prepared by the above preparation method2Se @ NiFe-LDH electrocatalyst suitable for catalyzing oxygen evolution reaction and hydrogen evolution reaction in alkaline electrolyte, and the application is to use core-shell Cu2The Se @ NiFe-LDH electrocatalyst is added into a 1mol/L KOH solution to be used as a working electrode, a saturated calomel electrode is used as a reference electrode, a platinum sheet is used as a counter electrode, and the catalytic activity of oxygen evolution reaction and hydrogen evolution reaction of the Se @ NiFe-LDH electrocatalyst and the full water-splitting performance of the Se @ NiFe-LDH electrocatalyst when the Se @ NiFe-LDH electrocatalyst is used as a dual-function electrode are tested.
Compared with the prior art, the invention has the main beneficial effects and advantages that:
(1) core of the inventionShell shaped Cu2The preparation method of the Se @ NiFe-LDH electrocatalyst overcomes the defects of aggregation, large particle size, wide particle size distribution range, small specific surface area and the like existing in the preparation of the nickel-iron hydrotalcite by the traditional coprecipitation method, and has the characteristics of large specific surface area, uniform size, thin lamella, good mechanical stability and the like.
(2) The core-shell Cu2Se @ NiFe-LDH electrocatalyst, Se element changes the electronic structure of Cu, so that Cu2Se has good conductivity and catalytic activity, Cu2The Se support obviously improves the conductivity and the dispersibility of the NiFe-LDH material and improves the catalytic performance.
(3) The core-shell Cu2The preparation method of the Se @ NiFe-LDH electrocatalyst is characterized in that the NiFe-LDH sheets prepared by the electrodeposition method have certain mechanical strength, and the NiFe-LDH is in Cu2Se nano-wires are distributed in a crossed way, so that active sites are fully exposed, and OH is facilitated-The access of (b) also facilitates the escape of gaseous products.
(4) The core-shell Cu2Cu in Se @ NiFe-LDH electrocatalyst2The synergistic effect between Se and NiFe-LDH improves the charge transmission of the nickel-iron hydrotalcite nano-sheets, overcomes the defects of poor conductivity and easy aggregation of the single NiFe-LDH nano-sheets, and improves the catalytic performance of the composite structure.
The specific implementation mode is as follows:
for a further understanding of the invention, reference will now be made to the following examples and drawings, which are not intended to limit the invention in any way.
Example 1:
(1)Cu2preparation of Se/CF
Soaking commercial foam copper with the specification of 3cm multiplied by 4cm in a hydrochloric acid solution with the concentration of 37% for 10 minutes, and washing for a plurality of times by using deionized water and absolute ethyl alcohol; the cleaned copper foam is put into 80mLNaOH and (NH)4)2S2O8The mixed solution is soaked for 20min, so that light blue Cu (OH) grows on the surface in situ2Nanowire, taking out Cu (OH) grown thereon2Washing the foam copper of the nanowire with deionized water, and drying in an oven at 60 ℃ for 6 h; drying the Cu (OH)2Placing the nanowire in a tube furnace, simultaneously placing 0.1g selenium powder at the front end of the tube furnace, heating to 400 ℃ at a speed of 5 ℃/min in a nitrogen atmosphere, keeping for 30min, taking out a sample after the tube furnace is naturally cooled, and washing with deionized water and ethanol for several times to obtain Cu 2Se/CF, drying for later use;
(2)Cu2preparation of Se @ NiFe-LDH/CF
With Cu2Se/CF as working electrode, Pt wire electrode as counter electrode, saturated calomel electrode as reference electrode, and Ni (NO) as electrolyte3)2And FeSO4Mixed aqueous solution of (3), Ni (NO)3)2And FeSO4The concentration of the copper is 0.2M and 0.1M respectively, and the copper is electrified for 120s under the condition that the potential is minus 1.0V to carry out the electrodeposition reaction so as to grow NiFe-LDH on the surface of the copper, thus preparing the nuclear shell Cu2Se@Ni2/ 3Fe1/3LDH/CF catalyst.
Example 2:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, setting the electrodeposition time to 60s to obtain copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst, noted as Cu2Se@Ni2/3Fe1/3-LDH/CF-60;
Example 3:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, the electrodeposition time is set to 90s to obtain copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst, which is denoted as Cu2Se@Ni2/3Fe1/3-LDH/CF-90;
Example 4:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, the electrodeposition time is set to 150s to obtain copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst, which is denoted as Cu 2Se@Ni2/3Fe1/3-LDH/CF-150;
Example 5:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, only Ni (NO) in the electrolyte solution was added3)2And FeSO4The concentration of the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is changed to 0.2M and 0.05M respectively to obtain the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst which is marked as Cu2Se@Ni2/3Fe1/3-LDH/CF-0.15;
Example 6:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, only Ni (NO) in the electrolyte solution was added3)2And FeSO4The concentration of the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is changed to 0.3M and 0.15M respectively to obtain the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst which is marked as Cu2Se@Ni2/3Fe1/3-LDH/CF-0.45;
Example 7:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, only Ni (NO) in the electrolyte solution was added3)2And FeSO4The concentration of the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is respectively changed to 0.1M and 0.2M to obtain the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst which is marked as Cu2Se@Ni2/3Fe1/3-LDH/CF-1:2;
Example 8:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, only Ni (NO) in the electrolyte solution was added3)2And FeSO4The concentration of the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is changed to 0.15M and 0.15M respectively to obtain the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst which is marked as Cu2Se@Ni2/3Fe1/3-LDH/CF-1:1;
Example 9:
(1)Cu2preparation of Se/CF
Reference was made to the procedure and conditions of step (1) in example 1.
(2)Cu2Preparation of Se @ NiFe-LDH/CF
Referring to the method and preparation conditions of step (2) in example 1, only Ni (NO) in the electrolyte solution was added3)2And FeSO4The concentration of the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is respectively changed to 0.225M and 0.075M, so that the copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is obtained and is marked as Cu2Se@Ni2/3Fe1/3-LDH/CF-3:1;
Comparative example 1:
referring to the method and preparation conditions in example 2, the only difference is that the nickel-iron hydrotalcite nanosheets, noted as Ni, are directly electrodeposited on the surface of the treated foamy copper2/3Fe1/3-LDH/CF;
Comparative example 2:
soaking commercial foam copper with the specification of 1cm multiplied by 2cm in a hydrochloric acid solution with the concentration of 37% for 10 minutes, and washing for a plurality of times by using deionized water and absolute ethyl alcohol; will be cleaned upThe copper foam of (2) was put into 80mL of NaOH and (NH)4)2S2O8The mixed solution is soaked for 20min, so that light blue Cu (OH) grows on the surface in situ2Nanowires, denoted Cu (OH)2NWs/CF;
Comparative example 3:
soaking commercial foam copper with the specification of 1cm multiplied by 2cm in a hydrochloric acid solution with the concentration of 37% for 10 minutes, and washing for a plurality of times by using deionized water and absolute ethyl alcohol, and marking as Cu foam;
FIG. 1 shows Cu obtained in example 12Se and Cu2XRD test pattern of Se @ NiFe-LDH sample. As can be seen from the figure, Cu2The Se catalyst has obvious characteristic peaks at 36.50 degrees, 42.69 degrees, 61.5 degrees and 73.69 degrees, is doped with a small amount of CuO, and shows diffraction peaks of 111, 200, 220 and 311 surfaces, which indicate that copper oxide exists in a sample. The catalyst has obvious characteristic peaks at 25.41 degrees and 43.91 degrees, corresponding to Cu 2222 and 504 planes of Se. Cu2Se@Ni2/3Fe1/3LDH samples in addition to CuO and Cu2Besides the characteristic peaks of Se, the characteristic peaks of 003, 006, 012, 015 and 018 planes of NiFe-LDH appear at 11.58 degrees, 23.33 degrees, 34.51 degrees, 39.59 degrees and 46.55 degrees, which proves that the core-shell copper selenide @ ferronickel hydrotalcite nanosheet electrocatalyst is successfully prepared.
FIG. 2 shows Cu obtained in example 12Scanning electron microscopy of Se nanowire samples. As can be seen from the figure, the nanowires are uniformly grown on the surface of the foam copper, the diameters of the nanowires are 150-250 nm, the shapes are regular, the sizes are uniform, the density is high, and the hydrotalcite deposition is facilitated. According to the literature, copper selenide has good electron transport capacity and certain oxygen evolution reaction catalytic activity, and is very beneficial to improving the catalytic activity of the catalyst OER.
FIG. 3 shows the core-shell Cu obtained in example 12Se@Ni2/3Fe1/3Scanning electron micrographs of LDH samples. As can be seen from the figure, the hydrotalcite nano-sheets are uniformly and alternately grown in Cu2On Se nano-wire, the ordered stereo structure greatly improves the specific surface area of the catalyst and is beneficial to OH-And release of gaseous productsAnd (4) placing. The thickness of the nano-sheet is less than 10nm, and the ultrathin structure is beneficial to the exposure of active sites and the improvement of electrocatalytic performance.
FIG. 4 shows core-shell Cu obtained in example 12Se@Ni2/3Fe1/3Transmission electron micrograph of LDH sample. As can be seen from the figure, NiFe-LDH nanosheets are in Cu2The length of the Se nanowire deposit is about 100-150 nm, the thickness of the nanosheet is less than 10nm, the nanosheet is uniformly distributed, and the appearance is good and is consistent with the scanning electron microscope image in figure 3.
FIG. 5 shows core-shell Cu obtained in example 12Se@Ni2/3Fe1/3High resolution transmission electron microscopy of LDH samples. From the figure, lattice fringes were clearly observed, the 0.25nm lattice fringe corresponding to the (012) crystal plane of NiFe-LDH, and the 0.34nm lattice fringe corresponding to Cu2Se (112) crystal face, and the existence of the several characteristic peaks proves that the NiFe-LDH nano-sheets are successfully deposited on Cu2Se surface.
FIG. 6 is an OER linear scan voltammogram of four samples from example 1, example 2, example 3, and example 4 in a 1mol/LKOH electrolyte, with comparative analysis of deposition time versus core-shell Cu 2Influence of Se @ NiFe-LDH electrocatalyst OER Activity, found at 50mA · cm-2Sample Cu obtained at a deposition time of 120 seconds at a current density of (1)2Se@Ni2/3Fe1/3The initial potential of LDH-120 is minimal and the catalyst has optimal catalytic activity.
FIG. 7 is an OER linear sweep voltammogram of three samples obtained in examples 1, 5 and 6 in a 1mol/L KOH electrolyte, comparing the total molar concentration of nickel iron ions in the deposition solution versus the core-shell Cu2The influence of the oxygen evolution reaction activity of the Se @ NiFe-LDH electrocatalyst is found to be 50mA · cm-2At a current density of 0.3M, Cu obtained at a total molar concentration of metal ions2Se@Ni2/3Fe1/3The initial potential of the-LDH-0.30 sample is the smallest, and the catalyst has the best catalytic activity.
FIG. 8 shows Cu obtained in example 12Se and Cu2Six samples of Se @ NiFe-LDH, example 7, example 8, example 9 and comparative example 1Linear scanning voltammogram of the product in 1mol/L KOH electrolyte. As can be seen from the figure, under the condition of ensuring that the concentration of the total metal ions in the ferronickel is not changed by 0.3M, only the proportion of the metal ferronickel ions is changed, and the proportion is 50 mA-cm-2At a current density of (2), Cu was obtained when the molar ratio of nickel to iron metal ions was 2:12Se@Ni2/3Fe1/3The LDH sample has the smallest initial potential and the largest gradient, so that the catalyst has the best catalytic activity in the proportion.
FIG. 9 shows Cu obtained in example 12Se@Ni2/3Fe1/3The time-current profile of the LDH electrocatalyst at a constant voltage of 1.45v (vs rhe) as shown, experienced 80 hours of testing with little apparent decrease in current density, indicating good long-term stability and durability of the catalyst.
FIG. 10 shows Cu obtained in example 12Se@Ni2/3Fe1/3Multistep chronopotentiometric plot of LDH electrocatalyst, current density from 100mA cm-2To 190mA cm-2The increase amplitude is 10 mA-cm every two hours-2There was substantially no change in current density during the first two hours, and the current density was relatively smooth with no significant fluctuations over the next twenty hours. This indicates that Cu2Se@Ni2/3Fe1/3the-LDH electrocatalyst has better catalytic activity and stability in the process of catalyzing OER.
FIG. 11 shows Cu obtained in example 1 of the present invention2Se and Cu2Electrochemical impedance spectra of Se @ NiFe-LDH, example 7, example 8, example 9 and comparative example 1 at different ratios of electrocatalyst open circuit potential of 1.48V (vs RHE) in 1mol/L KOH electrolyte, and electrochemical impedance of the catalyst was measured at open circuit potential in a stable 1mol/L KOH solution. As can be seen from the figure, Cu2Se@Ni2/3Fe1/3-LDH having a minimum charge transfer resistance, less than Cu for other metal proportions 2Se @ NiFe-LDH, also less than Cu2Se/CF and Ni2/3Fe1/3LDH/CF. This indicates that Cu2Se@Ni2/3Fe1/3Kinetic Process of LDH in comparison with other catalystsAnd is faster.
FIG. 12 shows Cu obtained in example 1 of the present invention2Se and Cu2HER linear sweep voltammograms of Se @ NiFe-LDH, comparative example 1, comparative example 2 and comparative example 3 in different proportions of the obtained electrocatalysts in a 1mol/L KOH electrolyte as shown in the figure, in which the Cu is present2Se@Ni2/3Fe1/3LDH electrocatalyst at 10mA cm-2The initial potential is minimum and the catalytic activity is optimal. Although the initial potential is smaller than that of a commercial Pt/C electrode, the Pt/C electrode has good application potential under high current density.
FIG. 13 shows Cu obtained in example 12Se and Cu2Scanning voltammogram of five samples obtained from Se @ NiFe-LDH, comparative example 1, comparative example 2 and comparative example 3 for fully electrolyzed water under a two-electrode system, in which five electrocatalysts, Cu2Se@Ni2/3Fe1/3the-LDH has the minimum initial potential and the highest catalytic activity, and is a bifunctional electrocatalyst with great application prospect.
The electrocatalytic performance test adopts a saturated calomel electrode as a reference electrode, a Pt electrode as a counter electrode, the sweeping speed is 5mV/s, the electrolyte is 1mol/LKOH electrolyte, all potentials are converted into reversible hydrogen potential (RHE), and the conversion formula is
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.