Wide-potential-range electro-catalytic material adapting to renewable electric power volatility and preparation method and application of wide-potential-range electro-catalytic material

Abstract

The invention relates to the technical field of catalytic materials, in particular to a wide-potential-range electro-catalytic material adapting to renewable power volatility and a preparation method and application of the wide-potential-range electro-catalytic material. The invention provides a wide-potential-range electro-catalytic material adapting to renewable power volatility. The wide-potential-range electro-catalytic material comprises a core layer of a nickel oxide containing Ni < 3 + > and Ni < 2 + > and a nickel-nitrogen-carbon catalyst shell layer wrapping the outer surface of the core layer. The invention provides a wide-potential-range electro-catalytic material adapting to renewable electric power volatility and a preparation method and application of the wide-potential-range electro-catalytic material. According to the nickel-nitrogen-carbon catalyst coated NiOx composite catalyst prepared by the method, reaction active sites are increased, high Faraday efficiency of CO2RR in a wide voltage range can be realized, high-selectivity CO production is realized, and cathode hydrogen evolution reaction (HER) is inhibited. The wide potential performance is very suitable for the volatility of renewable power, and the composite catalytic material provided by the invention can provide guarantee for the practical application of the renewable power driven CO2RR in the next step.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and particularly to a wide-potential-range electrocatalytic material adaptable to the volatility of renewable electricity, a preparation method thereof, and an application thereof. Background Art

[0002] Driving by renewable electricity such as solar energy and wind energy, reducing carbon dioxide reaction (CO2RR) to produce high-value chemicals or fuels under normal temperature and pressure is an efficient, green and emerging technology for promoting artificial carbon cycle and storing renewable energy.

[0003] Due to the strong stability of CO2 molecules and the competition of hydrogen evolution side reactions, the conversion efficiency and product selectivity of current CO2RR are not high. Among the 16 possible products of CO2RR, carbon monoxide (CO) product has a lower conversion energy barrier and is a crucial C1 building block in the chemical industry, which is widely used in the production of chemicals such as Fischer-Tropsch synthesis, acetic acid and methanol. Therefore, the scheme of directly electrocatalytically converting CO2 to CO (CO2-to-CO) driven by "green electricity" has the most practical application prospects.

[0004] However, due to the intermittency and volatility of renewable electricity, the output voltage is very unstable, which easily leads to hydrogen evolution side reactions in the CO2-to-CO process, resulting in a decrease in the selectivity / Faraday efficiency of product CO, or even the generation of other by-products. Currently, the voltage window for maintaining the CO Faraday efficiency above 90% in most CO2-to-CO processes is only 200 - 400 mV, which is still far from the requirements of mature applications. Therefore, maintaining high CO selectivity within a wide voltage range has become one of the key problems in the application of CO2RR technology. Developing an efficient and low-cost electrocatalyst for electrochemical CO2-to-CO within a wide potential range is imminent, which is of great significance for promoting the transformation of CO2RR technology from laboratory to mature application. Summary of the Invention

[0005] The present invention provides a wide-potential-range electrocatalytic material adaptable to the volatility of renewable electricity, a preparation method thereof, and an application thereof. The composite catalyst obtained by this method, in which nickel-nitrogen-carbon catalyst wraps NiOx, increases the reaction active sites, can achieve high Faraday efficiency of CO2RR within a wide voltage range, realize high-selectivity production of CO, and inhibit the cathodic hydrogen evolution reaction (HER). The wide-potential performance is very adaptable to the volatility of renewable electricity. The composite catalytic material provided by the present invention can provide guarantee for the next-step practical application of renewable-electricity-driven CO2RR.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides an electrocatalytic material with a wide potential range for adapting to the volatility of renewable electricity, including a core layer of nickel oxide containing Ni 3+ and Ni 2+ and a nickel-nitrogen-carbon catalyst shell layer wrapped around the outer surface of the core layer; based on the weight of the electrocatalytic material with a wide potential range for adapting to the volatility of renewable electricity, the mass of the core layer of nickel oxide containing Ni 3+ and Ni 2+ is 8-35 wt%.

[0007] Preferably, there is a strong interaction between the core layer of nickel oxide containing Ni 3+ and Ni 2+ and the nickel-nitrogen-carbon catalyst shell layer.

[0008] Preferably, the nickel oxide containing Ni 3+ and Ni 2+ is NiOx.

[0009] The nickel oxide containing Ni 3+ and Ni 2+ such as NiOx has nickel ions with two valence states at the same time. This rich oxidation state form is more conducive to the adsorption and activation of CO2. In addition, the nickel oxide containing Ni 3+ and Ni 2+ has a high content of Ni 3+ , and the charge transfer ability between Ni 3+ and Ni 2+ can act as an "electron reservoir". Therefore, the nickel oxide containing Ni 3+ and Ni 2+ has more effective electron structure regulation ability and charge transfer ability.

[0010] Furthermore, the nickel-nitrogen-carbon catalyst (Ni-N-C) shell layer inhibits the complete reduction of the nickel oxide containing Ni 3+ and Ni 2+ through physical isolation, keeping it in a partially oxidized state. The nickel oxide containing Ni 3+ and Ni 2+ is compounded with the nickel-nitrogen-carbon catalyst, which can well regulate the electron structure and charge transfer ability of the catalyst; in addition, the strong interaction at the interface between the nickel-nitrogen-carbon catalyst and the nickel oxide containing Ni 3+ and Ni 2+ results in the transfer of electrons from the nickel-nitrogen-carbon catalyst to the nickel oxide containing Ni 3+ and Ni 2+ , reducing the d-band center of Ni. This electron regulation may make the adsorption of *COOH intermediate more stable and promote the CO2RR reaction.

[0011] Based on the above, the nickel-containing3+ and Ni 2+ The nickel oxide containing Ni 3+ and Ni 2+ acts as an "electron reservoir" for the electronic structure regulation of the nickel-nitrogen-carbon catalyst. The nickel oxide containing Ni

[0012] The present invention also provides a preparation method of a wide-potential-range electrocatalytic material adapted to the volatility of renewable electricity, including: S1. Prepare nickel oxide containing Ni 3+ and Ni 2+ ; S2. Stir and mix the nickel oxide containing Ni 3+ and Ni 2+ , a zinc source, a nickel source, and 2-methylimidazole, and then dry and calcine in an inert atmosphere to obtain a wide-potential-range electrocatalytic material adapted to the volatility of renewable electricity.

[0013] The present invention uses a zinc source and 2-methylimidazole to obtain a zif8 precursor under stirring, and then the zif8 precursor is calcined with a nickel source to obtain a nickel-nitrogen-carbon catalyst. At the same time, during the calcination process, the nickel-nitrogen-carbon catalyst is wrapped on the surface of the nickel oxide containing Ni 3+ and Ni 2+ to obtain a wide-potential-range electrocatalytic material adapted to the volatility of renewable electricity.

[0014] Preferably, the content of Ni 3+ in the nickel oxide containing Ni 2+ and Ni 3+ is 68-72 wt%.

[0015] Preferably, in S1, the pH of the nickel source solution is adjusted to 9-11, and then dried and calcined to obtain nickel oxide containing Ni 3+ and Ni 2+ .

[0016] Preferably, the nickel source includes a nickel-containing salt. Preferably, the nickel source includes nickel nitrate, nickel sulfate or nickel chloride.

[0017] Preferably, the solvent in the nickel source solution is water.

[0018] Preferably, the solution for adjusting pH is sodium hydroxide solution and / or ammonia water.

[0019] Preferably, the solution for adjusting pH is 8-10 M sodium hydroxide solution.

[0020] Preferably, adjust the pH to 10.

[0021] Preferably, the drying temperature is 60 - 100 °C and the drying time is 6 - 10 h.

[0022] Preferably, the calcination temperature is 250 - 300 °C and the calcination time is 1 - 3 h.

[0023] Preferably, in S2, the molar ratio of nickel in nickel oxide containing Ni 3+ and Ni 2+ and zinc in zinc source is 1:(0.02 - 0.04):(2 - 5).

[0024] Preferably, the molar ratio of nickel in nickel oxide containing Ni 3+ and Ni 2+ and zinc in zinc source is 1:(0.02 - 0.04):3.

[0025] Preferably, the zinc source includes zinc-containing salts. Preferably, the zinc source includes zinc nitrate, zinc sulfate, zinc chloride or zinc acetate.

[0026] Preferably, the nickel source includes nickel-containing salts. Preferably, the nickel source includes nickel nitrate, nickel sulfate or nickel chloride.

[0027] Preferably, in S2, dimethylimidazole is mixed in a solvent to obtain solution A, nickel oxide containing Ni 3+ and Ni 2+ and the zinc source are mixed in a solvent to obtain solution B, and solution A and solution B are mixed and then a nickel source is added and stirred.

[0028] Preferably, the solvent includes methanol, ethanol or water.

[0029] Preferably, the stirring is as follows: stir for 1 - 5 h under an inert atmosphere and then stir for 8 - 10 h.

[0030] Preferably, the inert atmosphere includes nitrogen and / or argon.

[0031] Preferably, the calcination temperature is 900 - 1000 °C and the calcination time is 1 - 3 h.

[0032] More preferably, the calcination temperature is 900 - 950 °C and the calcination time is 1 - 2.5 h.

[0033] Preferably, the heating rate of calcination is 5 - 10 °C / min.

[0034] Preferably, the drying temperature is 60 - 100 °C and the drying time is 12 - 24 h.

[0035] Preferably, the inert atmosphere includes nitrogen and / or argon.

[0036] The present invention also provides an application of an electrocatalytic material with a wide potential range adapted to the volatility of renewable electricity in electrocatalytic production of carbon monoxide from carbon dioxide.

[0037] The present invention also provides a carbon dioxide electrocatalytic electrode, which includes an electrocatalytic material with a wide potential range adapted to the volatility of renewable electricity.

[0038] The present invention also provides a carbon dioxide catalytic reduction device, which includes a carbon dioxide electrocatalytic electrode.

[0039] Therefore, the present invention has the following beneficial effects: (1) The present invention utilizes NiOx wrapped by Ni-N-C to achieve multiple advantages of active site protection, electronic structure optimization, mass transfer efficiency improvement and product selectivity regulation through core-shell structure design, especially in inhibiting the HER reaction and improving the CO Faraday efficiency.

[0040] (2) For the NiOx@Ni-N-C catalyst provided by the present invention, the voltage window with a CO Faraday efficiency of more than 90% reaches more than 1200 mV, and the current density can reach 400 mA / cm 2 ; the stability time of maintaining 95% reaches more than 10 h.

[0041] (3) The present invention selects NiOx with two valence states of nickel ions, Ni 3+ and Ni 2+ This rich oxidation state form is more conducive to the adsorption and activation of CO2, helps to form an electron channel and a hydrogen bond network with the Ni-N-C catalyst, and accelerates charge transfer and intermediate conversion; resulting in the transfer of electrons from the nickel-nitrogen-carbon catalyst to the nickel oxide containing Ni 3+ and Ni 2+ , reducing the d-band center of Ni. This electronic regulation may make the adsorption of *COOH intermediate more stable and promote the CO2RR reaction. Description of the Drawings

[0042] Figure 1 is a comparison chart of CO Faraday efficiency for H-type cell tests; Figure 2 is a Faraday efficiency chart of the catalyst in Example 1 for flow cell tests; Figure 3 is an XRD comparison chart; Figure 4 is a Raman comparison chart; Figure 5 is a linear sweep voltammetry comparison chart; Figure 6Linear sweep voltammogram of the catalyst in Example 1 tested in an H-type cell under different saturated atmospheres; Figure 7 Stability diagram of Example 1 tested in an H-type cell; Figure 8 Performance diagram of different molar ratios of NiOx and zinc nitrate tested in an H-type cell; Figure 9 Performance diagram of different calcination temperatures tested in an H-type cell. Detailed implementation manners

[0043] The present invention will be further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0044] All raw materials in this part are purchased. Among them, commercial NiO is purchased from Aladdin, with a particle size less than 30 nm and a purity of 99.5%; Ni powder is purchased from Guangzhou Metal Metallurgy Co., Ltd., with a particle size of 200 - 300 nm and a purity of 99.9%.

[0045]

Example

[0046] (2) Preparation of the composite catalyst: Dissolve 0.0273 mol of dimethylimidazole in 25 mL of methanol solution, denoted as solution A. Take 0.001 mol of NiOx and 0.003 mol of Zn(NO3)2·6H2O and dissolve them in 88 mL of methanol solution (Zn:NiOx = 3:1), denoted as solution B. Slowly add A to B and stir evenly. Then take 2.5 mL of 10 mmol / L Ni(NO3)2·6H2O solution and add it to B. Stir for 2 h while passing Ar gas, then stir for 8 h and let it stand overnight. Then centrifuge and wash 3 times and dry in a 60°C oven. Place the sample in a tubular furnace under an N2 gas atmosphere, calcine at 900°C for 2 h to obtain the composite catalyst. In the composite catalyst, the mass of NiOx is 16 wt%. Denote it as NiOx@Ni-N-C.

[0047] Example 2 This example is basically the same as Example 1, and the difference is that: in (2), the calcination temperature is 950 °C.

[0048] Comparative Example 1 This comparative example is basically the same as Example 1, and the difference is that: the addition of NiOx is cancelled, and the obtained catalyst is denoted as Ni-N-C.

[0049] Comparative Example 2 This comparative example is basically the same as Example 1, and the difference is that: NiOx is replaced by an equimolar amount of Ni powder, and the obtained catalyst is denoted as Ni powder@Ni-N-C.

[0050] Comparative Example 3 This comparative example is basically the same as Example 1, and the difference is that: NiOx is replaced by an equimolar amount of commercial NiO, and the obtained catalyst is denoted as NiO@Ni-N-C.

[0051] Comparative Example 4 This comparative example is basically the same as Example 1, and the difference is that: the addition of NiOx is cancelled, and the addition of 10 mM Ni(NO3)2·6H2O in (2) is cancelled, and the obtained catalyst is denoted as N-C.

[0052] Comparative Example 5 Dissolve 0.44 mol Ni(NO3)2·6H2O in 100 mL of deionized water, adjust the pH to 10 with 10 mol / L sodium hydroxide, stir for 5 min, centrifuge twice, then place in an 80 °C oven and dry for 6 h. Subsequently, calcine the sample in a muffle furnace at 270 °C for 2 h to obtain NiOx, denoted as NiOx.

[0053] Comparative Example 6 This comparative example is basically the same as Example 1, and the difference is that: in (2), the dosage of NiOx is 0.0005 mol; denoted as Zn:NiOx = 3:0.5.

[0054] Comparative Example 7 This comparative example is basically the same as Example 1, and the difference is that: in (2), the dosage of NiOx is 0.003 mol; denoted as Zn:NiOx = 3:3.

[0055] Comparative Example 8 This comparative example is basically the same as Example 1, and the difference is that: in (2), the calcination temperature is 850 °C.

[0056]

Performance Test

[0057] CO Faradaic efficiency test: The test method was basically the same as that of the "Catalytic performance test", except that: the test environment was a flow cell, the anode and cathode compartments of the reaction cell were separated by a Sustainion X37-50 Grade RT anion exchange membrane, the area of the working electrode was 0.5 × 0.5 cm -2 , the counter electrode was a platinum mesh (1.4 cm × 1.4 cm), the reference electrode was a Hg / HgO electrode (filled with 1 M KOH), and the electrolytes were 1 M KOH and 0.1 M KOH + 0.9 M KCl solution.

[0058] The CO Faradaic efficiency tests were carried out on the catalysts obtained in Example 1 and Comparative Examples 1-5, and the results are as Figure 1 shown. Observation Figure 1It can be seen that the performance of Example 1 is significantly better than that of Comparative Examples 1-5. In Example 1, the voltage window where the CO Faraday efficiency remains above 90% in the H-type cell test reaches 700 mV. When the standard hydrogen potential is -1.1 V, the highest CO Faraday efficiency is approximately 100%. However, the CO Faraday efficiencies of the catalysts prepared in Comparative Examples 1-3 are all significantly lower than that of Example 1. Among them, the CO Faraday efficiencies of the catalysts prepared in Comparative Examples 4-5 are almost zero, and all hydrogen evolution occurs.

[0059] Furthermore, the CO Faraday efficiency of the catalyst in Example 1 was tested in a flow cell, and the electrolyte used was a mixed solution of 0.1 mol / L KOH and 0.9 mol / L KCl. Figure 2 It can be seen that the voltage window where the CO Faraday efficiency remains above 90% reaches more than 1200 mV. The optimal potential is -0.57 V, and the CO Faraday efficiency is approximately 100%. This proves that the catalyst obtained in Example 1 can be used as an electrocatalyst with a wide potential range to adapt to the volatility of renewable electricity.

[0060] XRD tests were carried out on the catalysts obtained in Example 1, Comparative Example 1, Comparative Example 3, and Comparative Example 4, and the results are as Figure 3 shown. It can be observed that all four catalysts have two weak peaks at 26.2° and 44.0°. These two diffraction peaks correspond to the diffraction peaks of the (002) crystal plane and (100) crystal plane of graphite carbon, respectively. From the XRD results, it can be seen that for Example 1 (NiOx@Ni-N-C) and Comparative Example 3 (NiO@Ni-N-C), there are obvious peaks of elemental Ni, indicating that most of the nickel oxide clusters have formed elemental Ni after high-temperature calcination. However, since the performances of Example 1 and Comparative Example 3 are different, it is possible that a part of the nickel oxide clusters have not been completely reduced to elemental Ni, further confirming that the NiOx clusters have greatly improved the performance of this catalyst. The XRD patterns of the remaining two comparative examples show the peaks of standard Ni-N-C and N-C.

[0061] Raman tests were carried out on the catalysts obtained in Example 1, Comparative Example 1, and Comparative Example 3, and the results are as Figure 4 shown. It can be observed that in the figure, both the D peak and the G peak are Raman characteristic peaks of the C atom crystal, at around 1350 cm -1 and 1580 cm -1 respectively. The D peak reflects the carbon defects in the lattice, and the G peak reflects the degree of carbonization of the material. From the Raman results, it can be seen that I D / I G is the intensity ratio of the D peak and the G peak; the smaller the value of I D / I G , the higher the degree of graphitization of carbon and the stronger the conductivity; I D / IG The larger the value, the more carbon defects are indicated. The I of Example 1 D / I G value is 0.874, while the I of Comparative Examples 1 and 3 D / I G values are 1.26 and 0.949 respectively. The I of Example 1 D / I G is the smallest and the graphitization degree is the highest.

[0062] Furthermore, linear sweep voltammetry tests were carried out on Example 1 and Comparative Examples 1 - 5 in a 0.5 mol / L KHCO3 solution saturated with CO2, and the results are as Figure 5 shown. It can be observed that the catalysts obtained in Comparative Examples 1 - 5 have a smaller current density on the LSV curve and poorer CO2RR performance. Example 1 has a lower initial potential and a higher current density. This indicates that Example 1 has the largest electrochemical response and activity to CO2. The results show that the NiOx cluster promotes the improvement of CO2RR performance.

[0063] Figure 6 This is the LSV diagram of Example 1 tested in an H-type cell under different saturated atmospheres. It can be seen that the performance of the NiOx@Ni-N-C catalyst under saturated CO2 gas is better than that under Ar gas. The lower initial potential and higher current density indicate that the catalyst has excellent CO2RR performance.

[0064] Figure 7 This is the stability diagram of Example 1 tested in an H-type cell. The long-term stability of the catalyst is crucial for realizing the scale-up of the reaction. Therefore, the NiOx@Ni-N-C catalyst was subjected to a long-term constant voltage electrolysis at -0.78 V (vs RHE) for 17 h. As time progresses, the selectivity of the NiOx@Ni-N-C catalyst remains basically unchanged, and the Faraday efficiency can still be maintained above 95%.

[0065] Figure 8 This is the performance diagram of different molar ratios of NiOx and Zn(NO3)2·6H2O tested in an H-type cell. The three molar ratios of Zn(NO3)2·6H2O:NiOx are 6:1, 3:1, and 3:3 respectively, and the best molar ratio is 3:1.

[0066] Figure 9 This is the performance diagram of different calcination temperature conditions tested in an H-type cell. The calcination temperatures of the NiOx@Ni-N-C catalyst are 850℃, 900℃, and 950℃ respectively. The performance of the catalyst calcined at 850℃ is significantly worse, and the performances of the catalysts calcined at 900℃ and 950℃ are relatively close. From the perspective of energy consumption saving, the best calcination temperature is 900℃.

Claims

1. A wide-potential-range electrocatalytic material adapted to the volatility of renewable electricity, characterized in that including Ni-containing 3+ and Ni 2+ a core layer of nickel oxide containing Ni 3+ and Ni 2+ and a nickel-nitrogen-carbon catalyst shell layer wrapped around the outer surface of the core layer; based on the weight of the electrocatalytic material with a wide potential range adapted to the volatility of renewable electricity, the mass of the core layer of nickel oxide containing Ni 2. The electrocatalytic material with a wide potential range adapted to the volatility of renewable electricity as described in claim 1, wherein The Ni-containing 3+ and Ni 2+ There is a strong interaction between the core layer of nickel oxide and the nickel-nitrogen-carbon catalyst shell layer.

3. The preparation method of the electrocatalytic material with a wide potential range adapted to the volatility of renewable electricity according to claim 1 or 2, characterized in that, Including: S1. Prepare nickel oxide containing Ni 3+ and Ni 2+ ; S2. Mix nickel oxide containing Ni 3+ and Ni 2+ with a zinc source, a nickel source, and 2-methylimidazole, stir and mix them, then dry and calcine them under an inert atmosphere to obtain an electrocatalytic material with a wide potential range suitable for the volatility of renewable electricity.

4. The preparation method according to claim 3, characterized in that, In S1, the pH of the nickel source solution is adjusted to 9 - 11, and then it is dried and calcined to obtain nickel oxide containing Ni 3+ and Ni 2+ .

5. The preparation method according to claim 3, characterized in that, In S2, containing Ni 3+ and Ni 2+ The molar ratio among nickel oxide containing Ni, Ni in the nickel source, and Zn in the zinc source is 1:(0.02~0.04):(2~5).

6. The preparation method according to claim 3, wherein, In S2, dimethylimidazole is mixed in a solvent to obtain solution A containing Ni 3+ and Ni 2+ nickel oxide and a zinc source are mixed in a solvent to obtain solution B. After solutions A and B are mixed, a nickel source is added and stirred and mixed.

7. The preparation method according to claim 3, characterized in that, In S2, the calcination temperature is 900 - 1000 °C, and the calcination time is 1 - 3 h.

8. Application of a wide - potential - range electrocatalytic material adapted to the volatility of renewable electricity as described in any one of claims 1 - 2 or a wide - potential - range electrocatalytic material prepared by the preparation method as described in any one of claims 3 - 7 in electrocatalytic production of carbon monoxide from carbon dioxide.

9. A carbon dioxide electrocatalytic electrode, characterized in that, Including a wide - potential - range electrocatalytic material adapted to the volatility of renewable electricity as described in any one of claims 1 - 2 or a wide - potential - range electrocatalytic material prepared by the preparation method as described in any one of claims 3 - 7.

10. A carbon dioxide catalytic reduction device, characterized in that, Including the carbon dioxide electrocatalytic electrode as described in claim 9.

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