CN113502496A - Polyaniline-coated oxalate self-supporting electrode and preparation method and application thereof - Google Patents

Polyaniline-coated oxalate self-supporting electrode and preparation method and application thereof Download PDF

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CN113502496A
CN113502496A CN202110780572.6A CN202110780572A CN113502496A CN 113502496 A CN113502496 A CN 113502496A CN 202110780572 A CN202110780572 A CN 202110780572A CN 113502496 A CN113502496 A CN 113502496A
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oxalate
polyaniline
electrode
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彭生杰
王辉
李林林
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Nanjing University of Aeronautics and Astronautics
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Abstract

The invention belongs to the technical field of electrocatalysis, and particularly discloses a polyaniline-coated oxalate self-supporting electrode and a preparation method and application thereof. According to the invention, oxalate active components with a two-dimensional sheet structure are grown in situ on a conductive substrate through a hydrothermal reaction, and then the oxalate active components are coated by polyaniline to prepare the high-activity oxalate self-supporting electrode. The oxalate growing in situ can improve the overall conductivity and structural stability of the catalytic electrode through the coating of polyaniline, and the strong synergistic effect between the oxalate and the polyaniline can promote the electronic delocalization between the d orbit and the pi conjugated ligand of the aniline, change the absorption and desorption Gibbs free energy of reactants and products on the surface of the electrode, and be more beneficial to the hydrogen evolution reaction. The method is simple to operate, the reaction conditions are mild, the obtained electrode has excellent hydrogen evolution reaction activity, has wide application prospect in the field of water electrolysis, and can provide a new idea for the structural design of similar self-supporting electrodes.

Description

Polyaniline-coated oxalate self-supporting electrode and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrocatalysis, and particularly relates to a polyaniline-coated oxalate electrode, a preparation method thereof, and application of the electrode in water electrolysis.
Background
Climate change is a global problem facing mankind, and fossil fuel combustion exacerbates environmental pollution. For the sustainable development of human beings, a green clean energy source is urgently needed. Hydrogen energy is known as a new energy source with the most application prospect, but the current water electrolysis hydrogen production technology is limited, a large amount of electric energy is consumed, and the problem of hydrogen production cost cannot be fundamentally solved. How to realize hydrogen production at low potential and further reduce the consumption of electric energy and the hydrogen production cost becomes the continuously struggling target of the majority of science and technology workers. According to theoretical research and a large number of experiments, the noble metal electrode has the optimal hydrogen evolution reaction performance, but the metal reserves are too small and expensive, so that the noble metal electrode cannot be applied to industrial production on a large scale. Therefore, it would be advantageous to develop a non-noble metal catalyst that is inexpensive and efficient to solve the above problems.
At present, the basic idea for developing non-noble metal catalysts is to increase the specific surface area and active sites of metals by carrying out structural modification, chemical doping and compounding with a conductive substrate on non-noble metals, thereby improving the electrocatalytic performance of non-noble metals and achieving the purpose of being comparable to noble metals. For example, chinese patent CN109267090B discloses an oxalate nano-array thin film electrode, wherein oxalate and transition metal salt are attached to a conductive substrate through hydrothermal reaction, which is essentially the substitution reaction of the two salts. According to the method, nickel oxalate or cobalt oxalate is used as an active material, the preparation of the active material and the combination of the active material and a conductive substrate are synchronously completed, and the obtained oxalate nanosheet array film is highly ordered and has the characteristic of oriented growth perpendicular to the surface of the conductive substrate. According to the patent, the oxalate nano array is synthesized in situ on the conductive substrate, so that the conductivity of the conductive substrate (such as porous titanium) can be utilized, the resistance between oxalate and the conductive substrate can be reduced through in situ synthesis, the high orderliness of the nano array is fully utilized, the migration of electrolyte is facilitated, the oxygen evolution performance of an electrode is obviously improved, and the oxalate nano array can be used as a super capacitor or an electrolytic water catalytic material. However, the conductive substrate titanium sheet or titanium mesh used in this patent is expensive, and has poor stability under a large current, the preparation cost of the electrode is high, and the electrocatalytic performance needs to be further improved.
Disclosure of Invention
The invention aims to provide a polyaniline-coated oxalate self-supporting electrode, which solves the problems of poor in-situ growth adhesiveness, stability and conductivity of the self-supporting electrode.
Meanwhile, the invention also provides a preparation method of the polyaniline-coated oxalate self-supporting electrode.
Finally, the invention further provides an application of the polyaniline-coated oxalate self-supporting electrode in water electrolysis.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a polyaniline-coated oxalate self-supporting electrode is characterized in that oxalate grows on a conductive substrate in situ, and the surface of the electrode is coated with polyaniline.
According to the invention, the oxalate active component grows in situ on the conductive substrate, and the polyaniline organic conductive layer is coated on the surface of the oxalate active component, so that the conductivity and the structural stability of the oxalate electrode are improved.
As a preferred embodiment, the conductive substrate is preferably nickel foam (Ni-foam). The conductive substrate (such as foamed nickel) is washed by hydrochloric acid solution to remove impurities in the conductive substrate before oxalate is grown in situ. The concentration of the hydrochloric acid solution is 0.1-0.4mol/L, and preferably 0.2 mol/L.
As a preferred embodiment, the oxalate salt is preferably cobalt oxalate (CoC)2O4) The cobalt oxalate is of a nanosheet structure.
According to the invention, the cobalt oxalate nanosheets grown in situ on the conductive substrate are coated by the polyaniline organic conductive layer, so that the overall conductivity and structural stability of the catalytic electrode can be improved, and the strong synergistic effect between the cobalt oxalate and the polyaniline can promote the electron delocalization between the d-orbit and the pi-conjugated ligand of the aniline, so that the absorption and desorption Gibbs free energy of reactants and products on the surface of the electrode is changed, and the hydrogen evolution reaction is facilitated.
In a preferred embodiment, the method for growing oxalate in situ on the conductive substrate comprises the following steps: soluble metal salt is used as a precursor, and oxalate grows in situ on a conductive substrate through a hydrothermal reaction with oxalate ligands under a weak acid condition. The soluble metal salt is a soluble metal nitrate, preferably cobalt nitrate (i.e., cobalt nitrate hexahydrate). The weakly acidic conditions are adjusted with an organic acid, preferably oxalic acid (i.e., oxalic acid dihydrate). The oxalate ligand is an organic ligand, preferably oxalic acid dihydrate. In this case, the weakly acidic condition may be adjusted by oxalic acid dihydrate. That is, oxalic acid dihydrate acts as both a ligand and an acidity regulator in this system.
As a preferred embodiment, the hydrothermal reaction process is: mixing a soluble metal salt precursor, an oxalate ligand and a solvent (water, preferably deionized water), placing the mixture into a polytetrafluoroethylene lining for ultrasonic dispersion, adding a conductive substrate (foamed nickel), then placing the mixture into a stainless steel reaction kettle, heating the mixture to 160-200 ℃ for hydrothermal reaction for 16-24 hours, and obtaining an electrode (namely an oxalate electrode) with oxalate growing in situ on the conductive substrate. The ultrasonic dispersion aims at uniformly dispersing the solution, and does not have special requirements on the power, frequency and time of the ultrasonic, for example, the ultrasonic frequency can be set to be 100Hz, and the ultrasonic time can be set to be 10 min. After the hydrothermal reaction is completed, the mixture is cooled to room temperature, washed (such as surface impurities washing) and dried (such as vacuum drying).
In a preferred embodiment, the molar ratio of the soluble metal salt (e.g. cobalt nitrate) to the oxalate ligand (e.g. oxalic acid dihydrate) is 1-2:1-2, preferably 1: 1.
In a preferred embodiment, the mass ratio of the foamed nickel to the cobalt nitrate hexahydrate to the oxalic acid dihydrate is 3-4:1-5: 1. The dosage of each substance in the hydrothermal reaction is as follows: to 30mL of water (preferably deionized water) were added 0.291g of cobalt nitrate hexahydrate and 0.126g of oxalic acid dihydrate.
As a preferred embodiment, the hydrothermal reaction conditions are: the reaction was carried out at 200 ℃ for 24 h.
As a preferred embodiment, the method for coating polyaniline on the surface of the electrode comprises the following steps: immersing an electrode with oxalate growing in situ on a conductive substrate into an aniline solution, adding a polymerization initiator to initiate polymerization reaction, and coating a polyaniline organic conductive layer on the surface of the electrode. The aniline solution can provide aniline monomers for generating polyaniline to coat oxalate active components and increase the structural stability of oxalate electrodes. And soaking the electrode in an aniline solution for 5-10min, and then adding a polymerization initiator to react under stirring at room temperature. The polymerization initiator is an inorganic peroxide, preferably water-soluble potassium persulfate (K)2S2O8). After the polymerization reaction is completed, the electrode is taken out, washed with ultrapure water and absolute ethyl alcohol in sequence, and dried (such as vacuum drying).
As a preferred embodiment, the concentration of the aniline solution is 6 to 12mmol/L, preferably 10 mmol/L. The concentration of the potassium persulfate is 0.5-1mmol/L, preferably 1 mmol/L. The mass ratio of the electrode with oxalate grown in situ on the conductive substrate to the aniline and the potassium persulfate is 85-90:2-4: 1. Specifically, the amount of each substance in the polymerization reaction is as follows: to 20mL of water (preferably deionized water) were added 18.6mg of aniline and 5.4mg of potassium persulfate.
As a preferred embodiment, the reaction time is 10 to 60min, preferably 25 to 30min, while stirring at room temperature. The rotation speed of stirring at room temperature is 300-700r/min, preferably 500 r/min. The stirring should not be too vigorous to prevent the in situ grown oxalate active ingredient from falling off.
A preparation method of a polyaniline-coated oxalate self-supporting electrode comprises the following steps:
(1) growing oxalate in situ on the conductive substrate to obtain an oxalate electrode;
(2) and coating polyaniline on the surface of the oxalate electrode to obtain the polyaniline-coated oxalate self-supporting electrode.
As a preferred embodiment, in step (1), the conductive substrate is preferably foamed nickel (Ni-foam). The conductive substrate (such as foamed nickel) is washed by hydrochloric acid solution to remove impurities in the conductive substrate before oxalate is grown in situ. The concentration of the hydrochloric acid solution is 0.1-0.4mol/L, and preferably 0.2 mol/L.
As a preferred embodiment, in the step (1), the oxalate is preferably cobalt oxalate (CoC)2O4) The cobalt oxalate is of a nanosheet structure.
As a preferred embodiment, in step (1), the method for growing oxalate in situ on the conductive substrate comprises: soluble metal salt is used as a precursor, and oxalate grows in situ on a conductive substrate through a hydrothermal reaction with oxalate ligands under a weak acid condition. The soluble metal salt is a soluble metal nitrate, preferably cobalt nitrate (i.e., cobalt nitrate hexahydrate). The weakly acidic conditions are adjusted with an organic acid, preferably oxalic acid (i.e., oxalic acid dihydrate). The oxalate ligand is an organic ligand, preferably oxalic acid dihydrate, wherein oxalate anions are used as ligands of the active component. In this case, the weakly acidic conditions can be adjusted by oxalic acid dihydrate, that is, oxalic acid dihydrate serves as both a ligand and an acidity regulator in the system.
As a preferred embodiment, the hydrothermal reaction process is: putting a soluble metal salt precursor, an oxalate ligand and a solvent (water, preferably deionized water) into a polytetrafluoroethylene lining for ultrasonic dispersion, adding a conductive substrate (foamed nickel), then putting the mixture into a stainless steel reaction kettle, and heating the mixture to 160-. The ultrasonic dispersion aims at uniformly dispersing the solution, and does not have special requirements on the power, frequency and time of the ultrasonic, for example, the ultrasonic frequency can be set to be 100Hz, and the ultrasonic time can be set to be 10 min. After the hydrothermal reaction is completed, the mixture is cooled to room temperature, washed (such as surface impurities washing) and dried (such as vacuum drying).
In a preferred embodiment, the molar ratio of the soluble metal salt (e.g. cobalt nitrate) to the oxalate ligand (e.g. oxalic acid dihydrate) is 1-2:1-2, preferably 1: 1.
In a preferred embodiment, the mass ratio of the foamed nickel to the cobalt nitrate hexahydrate to the oxalic acid dihydrate is 3-4:1-5: 1. The dosage of each substance in the hydrothermal reaction is as follows: to 30mL of water (preferably deionized water) were added 0.291g of cobalt nitrate hexahydrate and 0.126g of oxalic acid dihydrate.
As a preferred embodiment, the hydrothermal reaction conditions are: the reaction was carried out at 200 ℃ for 24 h.
As a preferred embodiment, in step (2), the method for coating polyaniline on the surface of the oxalate electrode comprises: and (3) immersing an oxalate electrode into an aniline solution, adding a polymerization initiator to initiate polymerization reaction, and coating polyaniline on the surface of the electrode to obtain the polyaniline-coated oxalate self-supporting electrode. The aniline solution is used for providing aniline monomers to polymerize to generate polyaniline, the oxalate electrode is firstly soaked in the aniline solution for 5-10min, and then a polymerization initiator is added to be stirred and react at room temperature. The polymerization initiator is an inorganic peroxide, preferably water-soluble potassium persulfate (K)2S2O8). After the polymerization reaction is completed, the electrode is taken out, washed with ultrapure water and absolute ethyl alcohol in sequence, and dried (such as vacuum drying).
As a preferred embodiment, the concentration of the aniline solution is 6 to 12mmol/L, preferably 10 mmol/L. The concentration of the potassium persulfate is 0.5-1mmol/L, preferably 1 mmol/L. The mass ratio of the oxalate electrode to the aniline to the potassium persulfate is 85-90:2-4: 1. Specifically, the amount of each substance in the polymerization reaction is as follows: to 20mL of water (preferably deionized water) were added 18.6mg of aniline and 5.4mg of potassium persulfate.
As a preferred embodiment, the reaction time is 10 to 60min, preferably 25 to 30min, while stirring at room temperature. The rotation speed of stirring at room temperature is 300-700r/min, preferably 500 r/min.
According to the invention, oxalate active components with a two-dimensional sheet structure are grown in situ on a conductive substrate through a hydrothermal reaction, and then the oxalate active components are coated by polyaniline to prepare the high-activity oxalate self-supporting electrode. The preparation method is simple and easy to operate, mild in reaction conditions and low in cost, and the obtained electrode has excellent hydrogen evolution reaction activity, has wide application prospect in the field of water electrolysis (especially in the aspect of hydrogen production by water electrolysis), and provides a new idea for the structural design of similar self-supporting electrodes.
An application of oxalate self-supporting electrode coated by polyaniline in the aspect of water electrolysis.
As a preferred embodiment, the application is in particular in the field of hydrogen production by electrolysis of water.
The invention has the beneficial effects that:
the invention integrates and prolongs the following strategies when preparing the polyaniline-coated oxalate self-supporting electrode: (1) altering the morphology of the electrochemically active component to increase the actual surface area without altering the frequency of conversion (TOF) at each site, thereby increasing the available active sites; (2) the organic conductive layer is coated on the surface of the electrode, so that the overall conductivity and structural stability of the catalytic electrode can be improved, and the strong synergistic effect between oxalate and polyaniline can promote the electronic delocalization between a d track and a pi conjugate ligand of aniline, so that the absorption and desorption Gibbs free energy of reactants and products on the surface of the electrode is changed, and the hydrogen evolution reaction activity of the electrode is improved; (3) the electrochemically active components are integrated with the conductive substrate to ensure low impedance of electron transmission pathways and reduce the possibility of physical delamination, so that electron coupling between the conductive substrate and the electrochemically active components produces a synergistic effect, thereby improving intrinsic activity. Based on the integration and application of the strategies, the oxalate active component with a nanosheet layered structure is grown in situ on the conductive substrate through a hydrothermal reaction to realize effective integration of the active component and the conductive substrate, and then the morphology structure of the material is changed through coating of polyaniline, so that the stability and the conductivity of the material are enhanced, and the catalytic electrode with relatively good hydrogen evolution reaction activity is prepared.
The preparation method provided by the invention is simple to operate, mild in reaction conditions and low in cost, and the obtained self-supported electrode has high stability and electrochemical activity, so that a new idea is provided for preparation of similar self-supported electrodes. Experimental results show that the polyaniline-coated oxalate self-supporting electrode has excellent hydrogen evolution reaction activity and good electro-catalysis performance, and has wide application prospects in the field of water electrolysis (particularly in the aspect of hydrogen production by water electrolysis).
Drawings
FIG. 1 is an SEM scanning electron micrograph of a polyaniline-coated oxalate free-standing electrode prepared in example 1 of the present invention;
FIG. 2 is an SEM scanning electron micrograph of an oxalate free-standing electrode prepared according to a comparative example of the present invention;
FIG. 3 is an XRD pattern of an oxalate free-standing electrode prepared according to example 1 of the present invention and a comparative example;
FIG. 4 is a graph comparing polarization curves of hydrogen evolution reactions of the electrodes prepared in the examples of the present invention and the comparative examples.
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings obtained in the experimental examples are briefly described above. It is understood that the above-mentioned drawings only show some experimental examples of the present invention and should not be considered as limiting the scope of protection of the claims in any way. For a person skilled in the art, it is possible to derive other relevant figures from these figures without inventive effort.
Detailed Description
In order to make the technical problems to be solved, the technical solutions adopted and the technical effects achieved by the present invention easier to understand, the technical solutions of the present invention are clearly and completely described below with reference to specific examples, comparative examples and experimental examples. It should be noted that the examples, comparative examples and experimental examples, in which specific conditions are not specified, were conducted according to conventional conditions or conditions recommended by the product manufacturer, and reagents, instruments and the like used therein were commercially available.
Example 1
In the polyaniline-coated oxalate self-supporting electrode in the embodiment, cobalt oxalate nanosheets grow in situ on the conductive substrate nickel foam, and the surface of the electrode is coated with a polyaniline organic conductive layer.
The preparation method of the polyaniline-coated oxalate self-supporting electrode in the embodiment comprises the following steps:
(1) in-situ growth of oxalate nanosheets on conductive substrates
Adding 0.291g of cobalt nitrate hexahydrate, 0.126g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, performing ultrasonic dispersion for 10min, adding 2X 3cm of cleaned Ni-foam serving as a conductive substrate, screwing the conductive substrate into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven for hydrothermal reaction, and setting the program: the temperature is 200 ℃, the time is 1440min, after the reaction is finished, after the oven is cooled to the room temperature, the electrode is taken out to be cleaned and dried, and the oxalate electrode is obtained;
(2) coating polyaniline organic conductive layer on electrode surface
Soaking an oxalate electrode in 20mL of 10mmol/L aniline solution for 5min, adding 5.4mg of potassium persulfate to initiate polymerization reaction, stirring at room temperature for reaction for 30min, taking out the electrode, washing and drying to obtain the polyaniline-coated oxalate self-supporting electrode.
In other embodiments of the present invention, the stirring time is set to 10min and 60min, respectively, and the other operations are the same as in example 1 to obtain 10min-PANI @ CoC in FIG. 42O4/NF、60min-PANI@CoC2O4and/NF shown as electrode.
Example 2
In the polyaniline-coated oxalate self-supporting electrode in the embodiment, cobalt oxalate nanosheets grow in situ on the conductive substrate nickel foam, and the surface of the electrode is coated with a polyaniline organic conductive layer.
The preparation method of the polyaniline-coated oxalate self-supporting electrode in the embodiment comprises the following steps:
(1) in-situ growth of oxalate nanosheets on conductive substrates
Adding 0.582g of cobalt nitrate hexahydrate, 0.126g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, ultrasonically dispersing for 10min, adding 2X 3cm of cleaned Ni-foam serving as a conductive substrate, screwing the conductive substrate into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven for hydrothermal reaction, and setting the program: the temperature is 160 ℃, the time is 1440min, after the reaction is finished, after the oven is cooled to the room temperature, the electrode is taken out to be cleaned and dried, and the oxalate electrode is obtained;
(2) coating polyaniline organic conductive layer on electrode surface
Soaking an oxalate electrode in 20mL of 10mmol/L aniline solution for 5min, adding 5.4mg of potassium persulfate to initiate polymerization reaction, stirring at room temperature for reaction for 30min, taking out the electrode, washing and drying to obtain the polyaniline-coated oxalate self-supporting electrode.
Example 3
In the polyaniline-coated oxalate self-supporting electrode in the embodiment, cobalt oxalate nanosheets grow in situ on the conductive substrate nickel foam, and the surface of the electrode is coated with a polyaniline organic conductive layer.
The preparation method of the polyaniline-coated oxalate self-supporting electrode in the embodiment comprises the following steps:
(1) in-situ growth of oxalate nanosheets on conductive substrates
Adding 0.291g of cobalt nitrate hexahydrate, 0.126g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, performing ultrasonic dispersion for 10min, adding 2X 3cm of cleaned Ni-foam serving as a conductive substrate, screwing the conductive substrate into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven for hydrothermal reaction, and setting the program: the temperature is 200 ℃, the time is 960min, after the reaction is finished, the electrode is taken out to be cleaned and dried after the oven is cooled to the room temperature, and the oxalate electrode is obtained;
(2) coating polyaniline organic conductive layer on electrode surface
Soaking an oxalate electrode in 20mL of 10mmol/L aniline solution for 5min, adding 5.4mg of potassium persulfate to initiate polymerization reaction, stirring at room temperature for 10min, taking out the electrode, washing and drying to obtain the polyaniline-coated oxalate self-supporting electrode.
Example 4
In the polyaniline-coated oxalate self-supporting electrode in the embodiment, cobalt oxalate nanosheets grow in situ on the conductive substrate nickel foam, and the surface of the electrode is coated with a polyaniline organic conductive layer.
The preparation method of the polyaniline-coated oxalate self-supporting electrode in the embodiment comprises the following steps:
(1) in-situ growth of oxalate nanosheets on conductive substrates
Adding 0.291g of cobalt nitrate hexahydrate, 0.252g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, performing ultrasonic dispersion for 10min, adding 2X 3cm of cleaned Ni-foam serving as a conductive substrate, screwing the substrate into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven for hydrothermal reaction, and setting the program: the temperature is 200 ℃, the time is 1440min, after the reaction is finished, after the oven is cooled to the room temperature, the electrode is taken out to be cleaned and dried, and the oxalate electrode is obtained;
(2) coating polyaniline organic conductive layer on electrode surface
Soaking an oxalate electrode in 20mL of 6mmol/L aniline solution for 5min, adding 5.4mg of potassium persulfate to initiate polymerization reaction, stirring at room temperature for reaction for 60min, taking out the electrode, washing and drying to obtain the polyaniline-coated oxalate self-supporting electrode.
Comparative example
According to the oxalate self-supporting electrode of the comparative example, cobalt oxalate nanosheets grow in situ on the conductive substrate foamed nickel.
The preparation method of the oxalate self-supporting electrode of the comparative example comprises the following steps:
adding 0.291g of cobalt nitrate hexahydrate, 0.126g of oxalic acid dihydrate and 30mL of deionized water into a polytetrafluoroethylene lining, performing ultrasonic dispersion for 10min, adding 2X 3cm of cleaned Ni-foam serving as a conductive substrate, screwing the conductive substrate into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven for hydrothermal reaction, and setting the program: the temperature is 200 ℃ and the time is 1440min, after the reaction is finished, the drying oven is cooled to the room temperature, the electrode is taken out to be cleaned and dried, and the CoC in the figure 4 is obtained2O4and/NF shown as electrode.
In other comparative examples of the invention, commercial Pt/C was selected as the electrode, see Pt/C/NF in FIG. 4, uniformly coated on cleaned nickel foam.
Examples of the experiments
(1) SEM scanning Electron microscopy analysis
SEM scanning electron microscope analysis of the polyaniline-coated oxalate free standing electrode prepared in example 1 is shown in FIG. 1. Meanwhile, the oxalate self-supporting electrode prepared in the comparative example was taken for SEM scanning electron microscopy analysis, and the results are shown in FIG. 2.
As can be seen from fig. 1 and 2, under the same scale, the layer structure of the uncoated polyaniline is thinner, while the nanosheet coated with polyaniline is significantly thicker, which illustrates that the preparation method of example 1 successfully coats the polyaniline on the oxalate active component.
(2) XRD analysis
A polyaniline-coated oxalate free-standing electrode (CoC) prepared in example 1 was taken2O4@ PANI), oxalate self-supporting electrode prepared in comparative example (CoC)2O4) XRD analysis was performed, and the results are shown in FIG. 3.
In FIG. 3, the three curves are sequentially CoC from top to bottom2O4、CoC2O4@ PANI and CoC2O4A standard card. As can be seen from FIG. 3, example 1 successfully synthesized pure CoC2O4After the polyaniline is coated, an XRD (X-ray diffraction) spectrum is not obviously changed because the polyaniline conductive polymer is an amorphous image and does not show an obvious characteristic peak in XRD characterization.
(3) HER test
The polyaniline-coated oxalate self-supporting electrode prepared in example 1 and the oxalate self-supporting electrode prepared in comparative example were used to form a three-electrode system, in which Ag/AgCl was used as a reference electrode, a carbon rod was used as a counter electrode, the self-supporting electrodes prepared in example 1 and comparative example were used as working electrodes, and HER performance test was performed in a 1.0M KOH solution, and the results are shown in fig. 4.
As can be seen from FIG. 4, the overpotential of the electrode prepared in example 1 at 10mA current was 48mV, which is close to 38mV for the Pt/C electrode at 10mA current.
As can be seen from fig. 4, among the self-supporting electrodes prepared with different polyaniline coating times, the electrode HER performance with the coating time of 30min is the best, the electrode with the coating time of 60min is slightly worse than the electrode with the coating time of 10min, and the HER performance of the electrode coated with polyaniline is obviously better than that of the electrode not coated with polyaniline, which indicates that the HER performance of the electrode coated with polyaniline can be obviously improved.
The experimental results show that the oxalate self-supporting electrode coated by polyaniline prepared by the invention has higher stability and electrochemical activity, and particularly, the best electrochemical hydrogen evolution reaction performance is obtained under the preferable polyaniline coating condition.
According to the invention, an oxalate active component is grown in situ on a Ni-foam substrate through a hydrothermal reaction, and then a high-activity oxalate self-supporting electrode is prepared through coating of polyaniline, wherein the electrode has excellent electrochemical hydrogen evolution reaction performance. In the electrode, the strong synergistic effect between oxalate and polyaniline can promote the electron delocalization between the d orbit and the pi conjugated ligand of aniline, and change the absorption and desorption Gibbs free energy of activated hydrogen atoms on the surface of the electrode, thereby being more beneficial to the hydrogen evolution reaction, and the obtained electrode completely meets the use requirements of hydrogen production by water electrolysis.
The preparation method provided by the invention is simple and easy to operate, mild in reaction conditions, low in cost, and good in performance of the obtained electrode, and has a wide application prospect in the field of water electrolysis (especially in the aspect of hydrogen production by water electrolysis).
The above are only preferred examples and experimental examples of the present invention, and do not limit the scope of the present invention. Many variations and/or modifications in the specific implementation of the invention may occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A polyaniline-coated oxalate self-supporting electrode is characterized in that: oxalate grows on the conductive substrate in situ, and polyaniline is coated on the surface of the electrode.
2. The polyaniline-coated oxalate self-supporting electrode of claim 1, wherein: the conductive substrate is foamed nickel.
3. The polyaniline-coated oxalate self-supporting electrode of claim 1 or 2, wherein: the oxalate is cobalt oxalate nanosheet.
4. The polyaniline-coated oxalate self-supporting electrode of claim 1, wherein: the method for in-situ growth of oxalate on the conductive substrate comprises the following steps: soluble metal salt is taken as a precursor, and oxalate grows in situ on a conductive substrate through hydrothermal reaction with oxalate ligands under the weak acidic condition; preferably, the soluble metal salt is cobalt nitrate, the oxalate ligand is oxalic acid dihydrate, and the weak acidic condition is adjusted by oxalic acid dihydrate; the molar ratio of the cobalt nitrate to the oxalic acid dihydrate is 1-2:1-2, preferably 1: 1; the conditions of the hydrothermal reaction are as follows: the reaction is carried out at 160 ℃ and 200 ℃ for 16-24h, preferably at 200 ℃ for 24 h.
5. The polyaniline-coated oxalate self-supporting electrode of claim 1, wherein: the method for coating polyaniline on the surface of the electrode comprises the following steps: immersing an electrode with oxalate growing in situ on a conductive substrate into an aniline solution, adding a polymerization initiator to initiate polymerization reaction, and coating polyaniline on the surface of the electrode; the concentration of the aniline solution is 6-12 mmol/L; the polymerization initiator is potassium persulfate, and the concentration is 0.5-1 mmol/L; the conditions of the polymerization reaction are as follows: the reaction is stirred at room temperature for 10-60min, preferably 25-30 min.
6. A method for preparing a polyaniline-coated oxalate self-supporting electrode as described in any one of claims 1 to 5, wherein: the method comprises the following steps:
(1) growing oxalate in situ on the conductive substrate to obtain an oxalate electrode;
(2) and coating polyaniline on the surface of the oxalate electrode to obtain the polyaniline-coated oxalate self-supporting electrode.
7. The method of preparing a polyaniline coated oxalate self-supporting electrode as claimed in claim 6, wherein: in the step (1), the conductive substrate is foamed nickel; and/or the oxalate is cobalt oxalate nanosheet.
8. The method of preparing a polyaniline coated oxalate self-supporting electrode as claimed in claim 6, wherein: in the step (1), the method for growing the oxalate in situ on the conductive substrate comprises the following steps: soluble metal salt is taken as a precursor, and oxalate grows in situ on a conductive substrate through hydrothermal reaction with oxalate ligands under the weak acidic condition; preferably, the soluble metal salt is cobalt nitrate, the oxalate ligand is oxalic acid dihydrate, and the weak acidic condition is adjusted by oxalic acid dihydrate; the molar ratio of the cobalt nitrate to the oxalic acid dihydrate is 1-2:1-2, preferably 1: 1; the conditions of the hydrothermal reaction are as follows: the reaction is carried out at 160 ℃ and 200 ℃ for 16-24h, preferably at 200 ℃ for 24 h.
9. The method of preparing a polyaniline coated oxalate self-supporting electrode as claimed in claim 6, wherein: the method for coating polyaniline on the surface of the oxalate electrode comprises the following steps: immersing an oxalate electrode into an aniline solution, adding a polymerization initiator to initiate polymerization reaction, and coating polyaniline on the surface of the electrode; the concentration of the aniline solution is 6-12 mmol/L; the polymerization initiator is potassium persulfate, and the concentration is 0.5-1 mmol/L; the conditions of the polymerization reaction are as follows: the reaction is stirred at room temperature for 10-60min, preferably 25-30 min.
10. Use of the polyaniline-coated oxalate self-supporting electrode as defined in any one of claims 1 to 5, or the polyaniline-coated oxalate self-supporting electrode prepared by the preparation method as defined in any one of claims 6 to 9, for electrolysis of water; the application in the aspect of hydrogen production by electrolyzing water is preferred.
CN202110780572.6A 2021-07-10 2021-07-10 Polyaniline-coated oxalate self-supporting electrode and preparation method and application thereof Pending CN113502496A (en)

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