Co-coated CeO2-x heterogeneous catalytic electrode and preparation method and application thereof

Abstract

The invention provides a Co (at) CeO2-x heterogeneous catalytic electrode as well as a preparation method and application thereof. The Co-coated CeO2-x heterogeneous catalytic electrode comprises foamed nickel and an electrocatalyst loaded on the surface of the foamed nickel, and the electrocatalyst comprises metal Co particles and CeO2-x with oxygen vacancy. The Co (at) CeO2-x heterogeneous catalytic electrode provided by the invention is prepared only through a process combining a room-temperature electrodeposition method and an air calcination method, has a three-dimensional self-supporting integrated structure, and also has a heterostructure and a porous nanosheet structure, so that more reaction active sites can be exposed, the interface charge transfer capability can be improved, and the catalytic performance can be improved. And the composite material has excellent activity and stability when being used as a cathode and an anode in the application of preparing formate and hydrogen by electrolyzing water under the assistance of glycerol.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic electrodes, in particular to a Co@CeO 2-x Heterogeneous catalytic electrode and preparation method and application thereof. BACKGROUND

[0002] Under the background of global energy transformation, the development of sustainable energy technology is crucial. Hydrogen energy has the advantages of abundant reserves and environmental friendliness, and has become one of the most potential renewable energy carriers. Water electrolysis is the preferred method for green hydrogen production, but the slow kinetics of anode oxygen evolution reaction (OER) significantly increases energy consumption and cost, becoming a bottleneck for efficient water electrolysis. Using thermodynamically more favorable glycerol electro-oxidation (GOR) to replace anode oxygen evolution reaction and coupling with hydrogen evolution reaction can not only reduce hydrogen production energy consumption, but also produce high-value-added products (such as formic acid), providing a promising solution for efficient and sustainable hydrogen production. In previous studies, noble metal materials have been widely used due to their high activity, but high cost and low reserves have become major obstacles to their large-scale development. Therefore, it is of important practical significance to design and synthesize non-noble metal catalysts with high catalytic performance for simultaneous electrocatalytic glycerol oxidation and hydrogen evolution. SUMMARY

[0003] (I) Technical problems solved

[0004] In view of the deficiencies in the prior art, the present application provides a Co@CeO 2-x Heterogeneous catalytic electrode and preparation method and application thereof, which combines electrodeposition method and air calcination to synthesize a heterogeneous material composed of Co nanoparticles and CeO 2-x to solve the problems raised in the above background.

[0005] (II) Technical solutions

[0006] To achieve the above object, the present application is implemented by the following technical solutions:

[0007] According to a first aspect of the present application, a Co@CeO 2-x Heterogeneous catalytic electrode is provided, comprising a foam nickel and an electrocatalyst loaded on the surface of the foam nickel, wherein the electrocatalyst comprises metal Co particles and CeO 2-x with oxygen defects.

[0008] Preferably, the electrocatalyst has a porous nanosheet structure, and the size of the porous nanosheet structure is 200-800 nm.

[0009] Preferably, the electrocatalyst has a heterogeneous structure composed of (100) plane of metal Co and (200) plane of CeO 2-x .

[0010] According to a second aspect of the present application, there is provided a Co@CeO 2-x A preparation method of a heterogeneous catalytic electrode, comprising the following steps:

[0011] (1) dissolving a cobalt salt, a cerium salt and an ammonium salt in water to obtain a salt solution;

[0012] (2) constructing a three-electrode structure, taking the foamed nickel as a working electrode, taking a saturated silver / silver chloride electrode as a reference electrode, taking a platinum sheet as a counter electrode, taking the salt solution as an electrolyte, and performing electrochemical deposition by applying a constant voltage to obtain a Co-Ce precursor;

[0013] (3) alternately cleaning the Co-Ce precursor with ethanol and distilled water, vacuum drying, and then placing the Co-Ce precursor in a muffle furnace for air calcination to obtain the Co@CeO 2-x heterogeneous catalytic electrode.

[0014] Preferably, in step (1), the molar ratio of the cobalt salt and the cerium salt is 1:0.1, and the cobalt salt and the cerium salt are respectively calculated by the moles of their metal elements.

[0015] The concentration of the ammonium salt in the salt solution is 0.01-0.03 g / mL.

[0016] Preferably, in step (1), the cobalt salt is selected from at least one of cobalt nitrate, cobalt chloride and cobalt sulfate.

[0017] The cerium salt is selected from at least one of cerium nitrate, cerium chloride or cerium sulfate.

[0018] The ammonium salt is selected from at least one of ammonium chloride, ammonium fluoride and ammonium sulfate.

[0019] Preferably, in step (2), the applied constant voltage is -1.0 to -3.0 V, and the time for applying the constant voltage is 400-1000 s.

[0020] Preferably, in step (2), the foamed nickel is sequentially subjected to ultrasonic treatment in hydrochloric acid, ethanol and distilled water for 15 min before use.

[0021] Preferably, in step (2), the size of the foamed nickel is: a thickness of 1.5 mm and an electrode area of 1×2 cm 2 .

[0022] Preferably, in step (3), the temperature for air calcination is 300-400℃, the heating rate is 5℃ / min, and the time for air calcination is 0.5-1.5 h.

[0023] According to a third aspect of the present application, there is provided a Co@CeO2-x The hetero-catalytic electrode or Co@CeO 2-x Application of the hetero-catalytic electrode as a cathode and an anode in glycerol-assisted water electrolysis for preparing formate and hydrogen.

[0024] Advantages

[0025] The present application provides a Co@CeO 2-x The present application provides a hetero-catalytic electrode and a preparation method and application thereof, which have the following advantages:

[0026] (1) The present application provides a Co@CeO 2-x The present application provides a hetero-catalytic electrode and a preparation method thereof, which are synthesized by a process combining a simple electrodeposition method and an air calcination method, and are composed of metal Co particles and CeO 2-x The surface of the hetero-catalytic electrode is a porous nanosheet structure, which is beneficial to exposing more reaction active sites, improving the interface charge transfer capacity, and accelerating the reaction kinetics process, thereby significantly improving the electrocatalytic performance of the material.

[0027] (2) The present application provides application of the hetero-catalytic electrode as a cathode and an anode in glycerol-assisted water electrolysis for preparing formate and hydrogen. 2-x The hetero-catalytic electrode can realize the co-electrolysis synthesis of formate and hydrogen at normal temperature and pressure, and exhibits high activity and excellent stability. By constructing an anion exchange membrane device, a current density of 100 mAcm -2 at a cell voltage of 1.51 V is realized, a formate faradic efficiency of 96% is achieved, and a formate yield of 61.79 mg h -1 cm -2 -1 is achieved. At the same time, the device can achieve a hydrogen production faradic efficiency close to 100%, which shows great application potential and economic value in the field of co-electrolysis synthesis of high-value chemicals. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 X-ray diffraction patterns of the electrocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application, wherein a is the XRD pattern of the Co@CeO 2-x electrocatalyst prepared in Example 1, b is the XRD pattern of the Co electrocatalyst prepared in Comparative Example 1, and c is the XRD pattern of the CeO2 electrocatalyst prepared in Comparative Example 2;

[0029] Figure 2 Scanning electron microscope images of the Co@CeO 2-x electrocatalyst prepared in Example 1 of the present application, wherein a is the SEM image at 5 μm, and b is the SEM image at 500 nm;

[0030] Figure 3 Co@CeO2 prepared for the embodiment 1 of the present application 2-x Transmission electron microscopy images of the electrocatalyst, wherein, a is TEM image at 50 nm, b is HRTEM image at 2 nm;

[0031] Figure 4 Co@CeO2 prepared for the embodiment 1 of the present application 2-x X-ray photoelectron spectroscopy images of the electrocatalyst, wherein, a is XPS image of Co 2p, b is XPS image of Ce 3d, c is XPS image of O 1s;

[0032] Figure 5 LSV curves of the electrocatalytic hydrogen evolution reaction (HER) of the catalytic electrode prepared for the embodiment 1, comparative example 1 and comparative example 2 under the condition of 1M KOH;

[0033] Figure 6 Electrocatalytic glycerol oxidation (GOR) performance images of the catalytic electrode prepared for the embodiment 1, comparative example 1 and comparative example 2, wherein, a is LSV curve in 0.1M glycerol and 1M KOH mixed solution, b is formate Faraday efficiency and yield comparison chart;

[0034] Figure 7 Co@CeO2 prepared for the embodiment 1 of the present application 2-x Heterogeneous catalytic electrode before and after the electrocatalytic glycerol oxidation reaction 1 H NMR spectrum;

[0035] Figure 8 Co@CeO2 prepared for the embodiment 1 of the present application 2-x Chronoamperometry curve of the heterogeneous catalytic electrode by constructing a three-electrode, wherein, a is HER chronoamperometry curve by constructing a three-electrode in 1M KOH solution, b is GOR chronoamperometry curve by constructing a three-electrode in 0.1M glycerol and 1M KOH mixed solution;

[0036] Figure 9 Co@CeO2 prepared for the embodiment 1 of the present application 2-x LSV curve of the hydrogen evolution coupled glycerol oxidation of the heterogeneous catalytic electrode, which is assembled into a membrane electrode assembly with 1M KOH as the cathode electrolyte and 0.1M glycerol and 1M KOH mixed solution as the anode electrolyte;

[0037] Figure 10 Co@CeO2 prepared for the embodiment 1 of the present application 2-xThe hetero-catalytic electrode was assembled into a membrane electrode assembly with 1M KOH as the catholyte and a mixed solution of 0.1M glycerol and 1M KOH as the anolyte, and a chronoamperogram was obtained after electrolysis of the membrane electrode assembly at a current density of 100mA cm -2 for 100h, and the product Faraday efficiency was detected every 20h. DETAILED DESCRIPTION

[0038] In order to better illustrate the content of the present application, the following specific examples are described.

[0039] Example 1

[0040] A Co@CeO 2-x The preparation method of the hetero-catalytic electrode comprises the following steps:

[0041] Step 1: First, a commercial nickel foam was cut into a size of 1.5mm in thickness and 1x2cm in length, and then ultrasonic cleaning was sequentially performed in a hydrochloric acid solution, deionized water and an ethanol solution for 15 minutes, to obtain a pretreated nickel foam, wherein the concentration of the hydrochloric acid solution is 1M. 2

[0042] Step 2: 6mmol of CoCl2·6H2O, 0.6mmol of Ce(NO3)3·6H2O and 1g of NH4Cl were weighed and added to 50mL of deionized water, and stirred uniformly to obtain a salt solution.

[0043] Step 3: A three-electrode system was constructed with the pretreated nickel foam as a working electrode, a saturated Ag / AgCl electrode as a reference electrode and a platinum sheet as a counter electrode, and was placed in an electrolytic cell containing the salt solution of step 1, and a constant voltage of-2V was applied to the working electrode, and a Co-Ce precursor was obtained after deposition for 800s.

[0044] Step 4: The Co-Ce precursor obtained in step 3 was cleaned with distilled water and ethanol alternately for 3 times, vacuum dried, and then placed in a muffle furnace for air calcination, with a heating rate of 5℃ / min, and calcination was performed at 300℃ for 1h, to obtain a hetero-catalytic electrode, which is denoted as Co@CeO 2-x .

[0045] Example 2

[0046] The preparation method of this example is the same as that of example 1, except that in step 2, 12mmol of CoCl2·6H2O, 1.2mmol of Ce(NO3)3·6H2O and 1g of NH4Cl were weighed and added to 50mL of deionized water, and stirred uniformly to obtain a salt solution.

[0047] Example 3

[0048] ​The preparation method of this example is the same as that of Example 1, except that in step 2, the amount of CoCl2·6H2O and Ce(NO3)3·6H2O remains unchanged, and the amount of ammonium chloride is 0.5 g.

[0049] Example 4

[0050] The preparation method of this example is the same as that of Example 1, except that in step 2, the amount of CoCl2·6H2O and Ce(NO3)3·6H2O remains unchanged, and the amount of ammonium chloride is 1.5 g.

[0051] Example 5

[0052] The preparation method of this example is the same as that of Example 1, except that in step 3, the voltage applied to the working electrode is -1 V.

[0053] Example 6

[0054] The preparation method of this example is the same as that of Example 1, except that in step 3, the voltage applied to the working electrode is -3 V.

[0055] Example 7

[0056] The preparation method of this example is the same as that of Example 1, except that in step 3, the duration of applying a constant voltage of -2 V for electrodeposition is 400 s.

[0057] Example 8

[0058] The preparation method of this example is the same as that of Example 1, except that in step 3, the duration of applying a constant voltage of -2 V for electrodeposition is 600 s.

[0059] Example 9

[0060] The preparation method of this example is the same as that of Example 1, except that in step 3, the duration of applying a constant voltage of -2 V for electrodeposition is 1000 s.

[0061] Example 10

[0062] The preparation method of this example is the same as that of Example 1, except that in step 4, the temperature for air calcination in the muffle furnace is 350°C.

[0063] Example 11

[0064] The preparation method of this example is the same as that of Example 1, except that in step 4, the temperature for air calcination in the muffle furnace is 400°C.

[0065] Example 12

[0066] The preparation method of this embodiment is the same as that of embodiment 1, except that, in step 4, the temperature of the air calcination in the muffle furnace is 300° C., and the calcination temperature is maintained for 0.5 h.

[0067] Example 13

[0068] The preparation method of this embodiment is the same as that of embodiment 1, except that, in step 4, the temperature of the air calcination in the muffle furnace is 300° C., and the calcination temperature is maintained for 1.5 hours.

[0069] Comparative Example 1

[0070] The preparation method of this comparative example is the same as that of Example 1, except that the electrolyte in step 2 does not contain Ce(NO3)3·6H2O, and the prepared catalytic electrode is recorded as Co.

[0071] Comparative Example 2

[0072] The preparation method of this comparative example is the same as that of Example 1, except that the electrolyte in step 2 does not contain CoCl2·6H2O, and the prepared catalytic electrode is recorded as CeO2.

[0073] Performance Testing

[0074] XRD analysis was performed on the electrocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2, respectively. Figure 1 As shown in Figure a, the prepared Co@CeO 2-x It is composed of two physical phases, Co and CeO2, corresponding to the standard cards of PDF#05-0727 and PDF#34-0394; Figures b and c show that the prepared Co and CeO2 only have diffraction peaks related to Co and CeO2, which proves that a catalytic material with two physical phases was prepared in Example 1.

[0075] The heterogeneous catalytic electrode prepared in Example 1 was characterized by SEM and TEM, respectively. Figure 2 and Figure 3 As shown, according to Figure 2 It can be seen that Co@CeO 2-x The electrocatalyst presents a porous nanosheet array structure and is evenly covered on the surface of the nickel foam substrate. Figure 3 Figure a (TEM) and Figure b (HRTEM) show that Co@CeO 2-x It has a porous nanosheet morphology, and Figure b shows two different lattice fringes with interlayer spacings of 0.217 nm and 0.270 nm, corresponding to Co(100) and CeO 2-x (200) crystal plane, which proves that Co@CeO 2-x Electrocatalysts have heterogeneous structures.

[0076] The heterogeneous catalytic electrode prepared in Example 1 was subjected to X-ray photoelectron spectroscopy (XPS) analysis, as shown in Figure 4 Co@CeO 2-x Co mainly exists in the form of Co 0 and Co 2+ ; Ce mainly exists in the form of Ce 3+ and Ce 4+ ; and lattice oxygen defects are observed in the O1s spectrum; the formation of these oxygen-deficient structures is beneficial to provide more active sites and regulate the electronic structure of the material, promoting the progress of the catalytic reaction.

[0077] Application Example 1

[0078] The catalytic electrodes prepared in Examples 1-13 and Comparative Examples 1-2 were used as cathodes and anodes, respectively, to assemble a membrane electrode assembly, 1M KOH was used as the cathode electrolyte, and a mixed solution of 0.1M glycerol and 1M KOH was used as the anode electrolyte, to test the hydrogen evolution coupled glycerol oxidation reaction (HER / / GOR), and a constant current of 100 mA cm -2 was applied for continuous electrolysis, and the anode electrolyte was collected for product (formate) detection.

[0079] Application Example 2

[0080] The method of this application example is the same as that of Application Example 1, except that a constant current of 200 mA cm -2 was applied.

[0081] Application Example 3

[0082] The method of this application example is the same as that of Application Example 1, except that a constant current of 300 mA cm -2 was applied.

[0083] Application Example 4

[0084] The method of this application example is the same as that of Application Example 1, except that a constant current of 400 mA cm -2 was applied.

[0085] Application Example 5

[0086] The method of this application example is the same as that of Application Example 1, except that a constant current of 500 mA cm -2 was applied.

[0087] Performance Test

[0088] A three-electrode system was constructed to test the HER of the catalytic electrodes prepared in Example 1, Comparative Example 1 and Comparative Example 2 in 1M KOH, as shown in Figure 5 Co@CeO 2-xThe hetero-catalytic electrode can achieve a current density of 100 mA cm-2 at a potential of only 97 mV, which is significantly better than the performance of Co and CeO2. -2 It can be seen that the synergistic effect between the materials is enhanced by the formation of the heterojunction, which significantly improves the catalytic performance of Co@CeO 2-x and makes it have excellent HER activity.

[0089] The catalytic electrodes prepared in Example 1, Comparative Example 1 and Comparative Example 2 were respectively subjected to glycerol oxidation performance test by electrocatalysis in a mixed electrolyte of 1 M KOH and 0.1 M glycerol by constructing a three-electrode system, as shown in Figure 6 . Among them, a is the linear voltammetry curve obtained by the test, b is the faradic efficiency of formate generation and the yield comparison chart. Compared with all the comparative sample, Co@CeO 2-x hetero-catalytic electrode has more excellent performance, which can drive the reaction at a current density of only 1.34 V vs. RHE at 100 mA cm -2 , and the faradic efficiency of formate generation reaches 96.1% and the yield is 30.73 mg h -1 cm -2 at a voltage of 1.4 V vs. RHE.

[0090] The solution before and after the glycerol reaction of the Co@CeO 2-x hetero-catalytic electrode prepared in Example 1 was subjected to 1 H NMR test, and the results are shown in Figure 7 . After 1 h of constant potential reaction, the glycerol nuclear magnetic signal is weakened, and the signal peak of formate salt appears at 8.3 ppm, indicating that the Co@CeO 2-x hetero-catalytic electrode prepared in Example 1 can effectively oxidize glycerol to formate salt.

[0091] The Co@CeO 2-x hetero-catalytic electrode prepared in Example 1 was subjected to chronoamperometry test, and the HER and GOR stability were evaluated by constructing a three-electrode system. As shown in Figure 8 a, the electrode can stably electrolyze for 15 h at a current density of-200 mA cm -2 ; as shown in Figure 8 b, at a current density of 200 mA cm -2 , the current density can quickly recover after supplementing glycerol in the reaction, and the voltage level remains relatively stable. It is proved that the Co@CeO 2-x hetero-catalytic electrode has excellent catalytic stability in hydrogen evolution and glycerol oxidation reaction.

[0092] The Co@CeO 2-xHeterogeneous catalytic electrodes were used as cathode and anode to assemble into a membrane electrode assembly (MEA), with 1M KOH as the cathode electrolyte and a mixed solution of 0.1M glycerol and 1M KOH as the anode electrolyte. Figure 9 As shown, at 100mA cm -2 At a current density of 1.51 V, the HER / / GOR system requires a voltage of 1.51 V, which is significantly lower than the 1.76 V required for the HER / / OER system. Furthermore, at this current density, the maximum Faradaic efficiency for formate production is 96%, with a yield of 61.79 mg h-1. - 1 cm -2 , proving that the catalytic electrode can exhibit excellent electrocatalytic performance when applied to HER / / GOR, and simultaneously achieve efficient formate synthesis and hydrogen production.

[0093] The catalytic electrode prepared in Example 1 was subjected to a chronoamperometric test in the constructed membrane electrode assembly to further investigate its stability in the HER / / GOR two-electrode system. Figure 10 As shown, at 100mA cm -2 At a constant current density, the assembled HER / / GOR electrolytic cell maintained stable catalytic activity over a 100-hour test, and the Faradaic efficiency of formate remained above 90%, demonstrating its promising industrial application prospects in the field of electrosynthesis of formate coupled to hydrogen production.

[0094] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A Co@CeO 2-x A heterogeneous catalytic electrode, characterized in that: The invention comprises nickel foam and an electrocatalyst loaded on the surface of the nickel foam, wherein the electrocatalyst comprises metal Co particles and CeO with oxygen defects. 2-x .

2. A Co@CeO according to claim 1 2-x A heterogeneous catalytic electrode, characterized in that: The electrocatalyst is in a porous nanosheet structure, and the size of the porous nanosheet structure is 200-800 nm.

3. A Co@CeO according to claim 1 2-x A heterogeneous catalytic electrode, characterized in that: The electrocatalyst has a heterostructure consisting of the (100) face of metal Co and CeO 2-x The (200) face composition.

4. A Co@CeO according to any one of claims 1 to 3 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: The following steps are involved: (1) dissolving cobalt salt, cerium salt and ammonium salt in water and stirring uniformly to obtain a salt solution; (2) constructing a three-electrode structure, using nickel foam as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, a platinum sheet as the counter electrode, and the salt solution as the electrolyte, applying a constant voltage for electrochemical deposition to obtain a Co-Ce precursor; (3) The Co-Ce precursor was alternately washed with ethanol and distilled water, vacuum dried, and then placed in a muffle furnace for air calcination to obtain the Co@CeO 2-x Heterogeneous catalytic electrodes.

5. A Co@CeO according to claim 4 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: In step (1), the molar ratio of the cobalt salt to the cerium salt is 1:0.1, and the cobalt salt and the cerium salt are respectively calculated based on the moles of their metal elements; The concentration of the ammonium salt in the salt solution is 0.01 to 0.03 g / mL.

6. A Co@CeO according to claim 4 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: In step (1), the cobalt salt is selected from at least one of cobalt nitrate, cobalt chloride, and cobalt sulfate; The cerium salt is selected from at least one of cerium nitrate, cerium chloride or cerium sulfate; The ammonium salt is selected from at least one of ammonium chloride, ammonium fluoride and ammonium sulfate.

7. The Co@CeO according to claim 4 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: In step (2), the applied constant voltage is -1.0 to -3.0 V, and the time for applying the constant voltage is 400 to 1000 s.

8. The Co@CeO according to claim 4 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: In step (2), the nickel foam is ultrasonically treated in hydrochloric acid, ethanol and distilled water in sequence for 15 minutes before use.

9. The Co@CeO according to claim 4 2-x The method for preparing a heterogeneous catalytic electrode is characterized by: In step (3), the air calcination temperature is 300-400° C., the heating rate is 5° C. / min, and the air calcination time is 0.5-1.5 h.

10. The Co@CeO according to any one of claims 1 to 3 2-x Heterogeneous catalytic electrode or Co@CeO prepared by the method according to any one of claims 4 to 9 2-x Application of heterogeneous catalytic electrodes as cathode and anode in glycerol-assisted water electrolysis to produce formate and hydrogen.

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