Three-dimensional porous array carbon electrode and preparation method and application thereof

Abstract

The application belongs to the technical field of electrocatalysis, and specifically discloses a three-dimensional porous array carbon electrode, which comprises a multi-scale pore structure composed of micropores and nanopores, has a specific surface area of not less than 200 m 2 g −1 , and a pore area of not less than 50 m 2 g −1 . The preparation method of the three-dimensional porous array carbon electrode and the application thereof in hydrogen production by electrolysis of water are disclosed. The three-dimensional porous array carbon electrode has a large pore area, high surface roughness, super-hydrophilic and gas-repellent properties and porous array channels, solves the shortcomings of traditional foam nickel electrodes and slurry casting electrodes in industrial application, and can realize large-scale, low-energy-consumption and high-stability industrial hydrogen production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalysis, in particular to a three-dimensional porous array carbon electrode and a preparation method and application thereof. BACKGROUND

[0002] Electrocatalytic gas evolution reactions play an important role in electrochemical energy conversion processes, among which water electrolysis is considered as a sustainable green hydrogen production technology, which consists of two gas evolution reactions, including the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). In recent years, the use of thermodynamically more favorable anodic oxidation reactions, such as urea oxidation reaction (UOR), can improve the energy conversion efficiency. Operating at large current density (> 500 mA cm −2 ) is crucial for the industrial application of water electrolysis technology, which can reduce capital investment. However, large current density operation requires high electron transmission rate, rapid supply / consumption of reactants and production / removal of products, which requires multi-dimensional design of high-performance catalytic electrodes.

[0003] So far, most of the reported catalysts are prepared in the form of powders, which are usually evaluated in the form of slurry added with polymer binder for dripping on the surface of glassy carbon electrodes, which inevitably leads to problems such as burial of active sites, hindered electron / substrate transmission, and catalyst falling off at large current density. In order to solve these problems, high surface area and low cost foam nickel (NF) self-supporting electrodes have been developed. However, NF electrodes still have technical defects: the excessively large pore size and high porosity of NF make it have a large number of voids that cannot load catalytic substances, thus limiting the active site area density; the disordered and random pore distribution in NF may capture the gas bubbles generated in the reaction, thus hindering their timely release from the electrode surface, and thus aggravating the negative impact of gas bubbles on catalytic performance at large current density. The above defects are the fundamental reasons for the limited catalytic performance.

[0004] Therefore, there is an urgent need for a self-supporting electrode with more ideal porous structure and higher chemical stability to overcome the limitations of traditional porous metal electrodes, achieve more excellent catalytic performance, and thus expand the applicability of self-supporting electrodes under different conditions. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a three-dimensional porous array carbon electrode and a preparation method and application thereof.

[0006] To solve the above technical problems, the technical solution provided by the present application is:

[0007] A three-dimensional porous array carbon electrode, comprising a multi-scale porous structure of micropores and nanopores, with a specific surface area of no less than 200 m 2 g −1 , a pore area of no less than 50 m 2 g −1 .

[0008] The three-dimensional porous array carbon electrode, preferably, has a water droplet contact angle of no more than 10° and a bubble contact angle of no less than 160°.

[0009] The three-dimensional porous array carbon electrode, preferably, has a roughness of no less than 2800.

[0010] The three-dimensional porous array carbon electrode, preferably, only needs a low potential of 1.360 V to provide a large current density of 1000 mA cm −2 in a urea oxidation reaction.

[0011] As a general inventive concept, the present application also provides a preparation method of a three-dimensional porous array carbon electrode, comprising the following steps:

[0012] (1) ultrasonic treatment of a GONR solution, then transferred to a high-pressure reactor for hydrothermal self-assembly reaction to obtain a hydrogel;

[0013] (2) cutting the hydrogel into a thin piece, placed on a copper block pre-cooled with liquid nitrogen for ice template treatment, then freeze-dried, and finally annealed to obtain a three-dimensional array carbon film electrode substrate;

[0014] (3) depositing active substances on the three-dimensional array carbon film electrode substrate by electrodeposition to obtain the three-dimensional porous array carbon electrode.

[0015] The preparation method, preferably, in step (3), the active substance is at least one of Ni(OH)2, Ru or NiFe(OH) x (x is 2-3).

[0016] The preparation method, preferably, in step (3), the electrodeposition uses a standard three-electrode system, with the three-dimensional array carbon film electrode substrate, Ag / AgCl electrode and graphite rod as the working electrode, reference electrode and counter electrode, respectively, and the three-dimensional porous array carbon electrode is obtained after electrodeposition at a constant potential of−0.4 V ~−1.2 V vs. Ag / AgCl in the electrolyte for 5-15 min and then washing.

[0017] Preferably, in step (2), the temperature of the freeze-drying is -40 to -60 ℃, and the time is 1-8 h.

[0018] The annealing treatment is performed in an inert atmosphere, and the temperature of the annealing is 700-900 ℃, and the time of the annealing is 0.5-2 h.

[0019] Preferably, in step (1), the temperature of the hydrothermal self-assembly reaction is 120-180 ℃, and the time is 6-12 h.

[0020] As a general inventive concept, the application also provides a use of the above-mentioned three-dimensional porous array carbon electrode or the three-dimensional porous array carbon electrode prepared by the above-mentioned preparation method in electrolytic hydrogen production.

[0021] Compared with the prior art, the application has the following advantages:

[0022] (1) The three-dimensional porous array carbon electrode has a multi-scale pore structure composed of abundant micropores and nanopores, so that it has a high surface area, allows a large amount of active material to be loaded, and thus has a high active site density.

[0023] (2) The three-dimensional porous array carbon electrode has a high surface roughness and super gas-repellent property, and can timely remove a large amount of gas bubbles generated under an industrial-grade large current, thereby ensuring efficient operation of the reaction.

[0024] (3) The large number of porous array channels in the three-dimensional porous array carbon electrode can provide favorable paths for the transmission of ions, gas and electrons, and exhibit excellent mass transfer capacity under an industrial-grade large current, thereby realizing low energy consumption and high-stable efficient hydrogen production.

[0025] (4) The low-crystallinity active material obtained by the electrodeposition method has high intrinsic active catalytic sites.

[0026] In summary, the three-dimensional porous array carbon electrode prepared by the preparation method of the application has a large pore area, a high surface roughness, super hydrophilic and gas-repellent properties, and porous array channels, and solves the shortcomings of traditional foam nickel electrodes and slurry casting electrodes in industrial applications, and can realize large-scale, low-energy-consumption and high-stable industrial hydrogen production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a process flow diagram for preparing the three-dimensional porous array carbon electrode in Example 1 of the application.

[0028] Figure 2 The figure is a real photo of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE prepared in Example 1 of the application.

[0029] Figure 3 Nitrogen adsorption-desorption curves and mercury intrusion test results of the three-dimensional porous array carbon electrode and the foam nickel electrode prepared for Example 1 and Comparative Example 1 of the present application: nitrogen adsorption-desorption curve graph (a) and pore area and roughness obtained by mercury intrusion test (b).

[0030] Figure 4 Scanning electron microscope images (a-c) and element distribution graph (d) of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE prepared in Example 1 of the present application.

[0031] Figure 5 X-ray diffraction pattern (a) and transmission electron microscope image (b) of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE prepared in Example 1 of the present application.

[0032] Figure 6 Scanning electron microscope images of NiFe(OH) x / ACE (a, b) prepared in Example 2 of the present application and Ru / ACE (c, d) prepared in Example 3.

[0033] Figure 7 Liquid and gas contact angles of the three-dimensional porous array carbon electrode, the foam nickel electrode and the slurry cast electrode prepared in Example 1 and Comparative Examples 1, 2 of the present application.

[0034] Figure 8 Optical photographs of bubble detachment from the surface of the three-dimensional porous array carbon electrode, the foam nickel electrode and the slurry cast electrode prepared in Example 1 and Comparative Examples 1, 2 of the present application at 1000 mA cm −2 and the corresponding schematic diagrams at a scale of 0.5 mm (a) and bubble size distribution graph (b).

[0035] Figure 9 CV curves (a) and site density (b) of the three-dimensional porous array carbon electrode, the foam nickel electrode and the slurry cast electrode prepared in Example 1 and Comparative Examples 1, 2 of the present application containing Ni 2+ / Ni 3+ oxide peaks.

[0036] Figure 10 Polarization curves (a), ΔE / Δlog|j| ratio at different current densities (b) and steady state test graph (c) of the three-dimensional porous array carbon electrode, the foam nickel electrode, the slurry cast electrode and the pure carbon electrode (ACE) without electrodeposition of active species prepared in Example 1 and Comparative Examples 1, 2 of the present application.

[0037] Figure 11Porous three-dimensional array carbon electrodes prepared for Inventive Examples 2, 3 in 1 M KOH electrolyte, OER (a) and HER (b) polarization curves and their Δ E / Δlog| j | ratio (c, d).

[0038] Figure 12 Two-electrode electrolysis of urea schematic (a) and polarization curves of electrolysis of urea / water (b) constructed for porous three-dimensional array carbon electrodes prepared for Inventive Example 1, 2 and Inventive Example 3.

[0039] Figure 13 Scanning electron micrographs of Ni(OH)2 / ACE-1 (a, b) prepared for Inventive Example 4 and Ni(OH)2 / ACE-20 (c, d) prepared for Inventive Example 5.

[0040] Figure 14 Pore area and porosity of Ni(OH)2 / ACE with different pore sizes in Inventive Examples.

[0041] Figure 15 Polarization curves of UOR (a) and their Δ E / Δlog| j | ratio (b) of Ni(OH)2 / ACE with different pore sizes in Inventive Examples. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the following will be a more comprehensive and detailed description of the present application in conjunction with the drawings and preferred embodiments of the specification, but the scope of protection of the present application is not limited to the following specific embodiments.

[0043] Unless otherwise defined, all of the professional terms used in the following are the same as those commonly understood by those skilled in the art. The professional terms used in this paper are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application.

[0044] Unless otherwise specified, the various reagents, raw materials used in the present application are commercially available or can be prepared by known methods.

[0045] Three-electrode gas evolution reaction test method involved in the following examples: All electrochemical tests were performed using a Shanghai Chenhua electrochemistry workstation through a three-electrode system. For UOR, the test was performed in 1 M KOH electrolyte containing 0.33 M urea, with a Hg / HgO electrode and a graphite rod as the reference electrode and the counter electrode, respectively, and self-supported Ni(OH)2 / ACE, Ni(OH)2 / NF and ACE electrodes as the working electrode, and Ni(OH)2 / SCE cast into a glassy carbon electrode as the working electrode. For OER and HER, the test was performed in 1 M KOH electrolyte. The polarization curves of the catalysts were obtained at a scan rate of 2 mV s −1 -1. Finally, the long-term stability of the porous array carbon electrode at a constant current density was evaluated by chronopotentiometry.

[0046] Two-electrode urea / water electrolysis test method involved in the following examples: For the two-electrode urea-assisted water electrolysis system and the traditional water electrolysis system, Ni(OH)2 / ACE and Ru / ACE were used as the anode and the cathode, respectively, and the performance test was performed in 1 M KOH and 1 M KOH electrolyte containing 0.33 M urea.

[0047] Example 1:

[0048] A method for preparing a three-dimensional porous array carbon electrode of the present application, the process flow chart thereof is shown as Figure 1 , comprising the following steps:

[0049] (1) 7 mg mL −1 of GONR solution (90 vol% water and 10 vol% ethanol mixture as solvent) was transferred to a high-pressure reaction kettle after ultrasonic treatment for 10 minutes, and hydrothermal self-assembly was performed at 120 °C for 12 hours to obtain a hydrogel.

[0050] (2) The hydrogel was cut into a thin piece and placed on a copper block pre-cooled with liquid nitrogen for ice template treatment to realize the directional freezing process, and then freeze-dried at a temperature of -45 °C for 5 h, and then annealed at 800 °C for 1 h under an argon atmosphere to obtain a three-dimensional array carbon film electrode base ACE with high conductivity.

[0051] (3) The active material Ni(OH)2 is deposited on the three-dimensional array carbon film electrode substrate ACE by electrodeposition. The electrodeposition adopts a standard three-electrode system, and ACE, Ag / AgCl electrode and graphite rod are used as the working electrode, reference electrode and counter electrode respectively. The three-dimensional porous array carbon electrode Ni(OH)2 / ACE is obtained by electrodeposition at a constant potential of-1.2 V vs. Ag / AgCl in an electrolyte of 15 mM Ni(NO3)2·6H2O for 10 minutes, and then washing with water. The actual graph of the three-dimensional porous array carbon electrode is shown in FIG. 1. Figure 2

[0052] Example 2

[0053] The preparation method of the three-dimensional porous array carbon electrode in this embodiment includes the following steps:

[0054] (1) 7 mg mL −1 of GONR solution (90 vol% water and 10 vol% ethanol mixture as solvent) is ultrasonically treated for 10 minutes and then transferred to a high-pressure reaction kettle for hydrothermal self-assembly at 120 °C for 12 hours to obtain a hydrogel.

[0055] (2) The hydrogel is cut into a thin piece and placed on a copper block pre-cooled with liquid nitrogen for ice template processing to realize a directional freezing process, and then freeze-dried at a temperature of-45 °C for 5 hours. Then, the freeze-dried product is annealed at 800 °C for 1 hour under an argon atmosphere to obtain a three-dimensional array carbon film electrode substrate ACE with high conductivity.

[0056] (3) The active material NiFe(OH) x is deposited on the three-dimensional array carbon film electrode substrate ACE by electrodeposition. The electrodeposition adopts a standard three-electrode system, and ACE, Ag / AgCl electrode and graphite rod are used as the working electrode, reference electrode and counter electrode respectively. The three-dimensional porous array carbon electrode NiFe(OH) x / ACE is obtained by electrodeposition at a constant potential of-1.2 V vs. Ag / AgCl in an electrolyte of 12 mM Ni(NO3)2·6H2O and 3 mM Fe(NO3)3·9H2O for 10 minutes and then washing with water.

[0057] Example 3

[0058] The preparation method of the three-dimensional porous array carbon electrode in this embodiment includes the following steps:

[0059] (1) 7 mg mL −1 ​The GONR solution (90 vol% water and 10 vol% ethanol mixture as solvent) was transferred into a high-pressure reaction kettle after ultrasonic treatment for 10 min, and hydrothermal self-assembly was carried out at 120 °C for 12 h to obtain the hydrogel.

[0060] (2) The hydrogel was cut into thin slices and placed on a copper block pre-cooled with liquid nitrogen for ice template processing to achieve a directional freezing process, and then freeze-dried at a temperature of -45 °C for 5 h. Then, the three-dimensional array carbon film electrode substrate ACE with high electrical conductivity was obtained by annealing at 800 °C for 1 h under an argon atmosphere.

[0061] (3) The active material Ru was deposited on the three-dimensional array carbon film electrode substrate ACE by electrodeposition. The electrodeposition was carried out using a standard three-electrode system, with ACE, Hg / HgO electrode and graphite rod as working electrode, reference electrode and counter electrode, respectively, in 1 M KOH and 1 mM Ru(NH3)6Cl3 electrolyte, at a constant potential of -0.4 V vs. RHE for 10 min, and then washed with water to obtain the three-dimensional array carbon film electrode Ru / ACE.

[0062] Comparative Example 1:

[0063] The preparation method of the carbon electrode in the present comparative example comprises the following steps:

[0064] The active material Ni(OH)2was deposited on the electrode substrate nickel foam (NF) by electrodeposition. The electrodeposition was carried out using a standard three-electrode system, with NF, Ag / AgCl electrode and graphite rod as working electrode, reference electrode and counter electrode, respectively, in 15 mM Ni(NO3)2·6H2O electrolyte, at a constant potential of -1.2 V vs. Ag / AgCl for 10 min, and then washed with water to obtain the carbon electrode Ni(OH)2 / NF.

[0065] Comparative Example 2:

[0066] The preparation method of the carbon electrode in the present comparative example comprises the following steps: a mixture of 1 mg of Ni(OH)2 / ACE prepared in Example 1, 0.25 mL of ethanol and 20 μL of Nafion solution was ultrasonically prepared into a slurry to obtain a uniform ink, and then 30 μL of the ink was dropped onto a glassy carbon electrode to obtain the Ni(OH)2 / SCE.

[0067] As shown in Figure 3 The nitrogen adsorption-desorption curves and mercury intrusion test results of the three-dimensional porous array carbon electrodes and nickel foam electrodes prepared in Example 1 and Comparative Example 1 show that the BET specific surface area and pore area of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE are 222.4 m 2 g−1 and 55.2 m 2 g −1 This is significantly higher than the 0.1 m of Ni(OH)2 / NF in nickel foam electrodes. 2 g −1 and 1.9 m 2 g −1 The high pore area is beneficial for exposing more active sites. Ni(OH)2 / ACE also has a high roughness (2815.3), which is two orders of magnitude higher than Ni(OH)2 / NF (21.6).

[0068] like Figure 4 As shown, the scanning electron microscope (SEM) images (a-c) and elemental distribution map (d) of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE prepared in Example 1 are shown. The cross-section of the carbon electrode has a vertically arranged porous channel structure with a size distribution of about 5-10 µm. The surface has a uniform porous honeycomb structure, and the electrodeposited Ni(OH)2 is uniformly distributed.

[0069] like Figure 5 As shown, the X-ray diffraction pattern of the three-dimensional porous array carbon electrode Ni(OH)2 / ACE prepared in Example 1 shows weak characteristic peaks of graphite carbon and Ni(OH)2, indicating that it has low crystallinity; the transmission electron microscopy image shows that the electrodeposited Ni(OH)2 is a nanoflower-like structure assembled from countless nanosheets, with a lateral size of about 50 nm, and is uniformly distributed on the carbon substrate.

[0070] like Figure 6 As shown, the NiFe(OH) prepared in Example 2 x Scanning electron microscopy images of Ru / ACE (a, b) and Ru / ACE (c, d) prepared in Example 3, with electrodeposition of NiFe(OH). x Carbon electrode (NiFe(OH)) obtained with Ru nanoparticles x The / ACE and Ru / ACE also have porous array structures with 5–10 µm channels and uniformly porous honeycomb structures.

[0071] To investigate the surface wettability of the catalyst, contact angle tests were conducted using water droplets and bubbles, such as... Figure 7 As shown. The water droplet contact angles of Ni(OH)2 / ACE, Ni(OH)2 / NF, and Ni(OH)2 / SCE in Example 1 and Comparative Examples 1 and 2 are approximately 0°, 82°, and 135°, respectively, indicating that Ni(OH)2 / ACE has superhydrophilicity, which is beneficial for wetting the electrolyte; their bubble contact angles are approximately 170°, 130°, and 51°, respectively, indicating that Ni(OH)2 / ACE has superhydrophobicity, weak adhesion to bubbles, and can cause the generated bubbles to fall off quickly.

[0072] To quantitatively analyze bubble release behavior, data were collected at 1000 mA cm⁻¹. −2 The size of the detached bubbles, such as Figure 8 As shown in the figure. The results show that most (>90%) of the bubbles in Ni(OH)2 / ACE are distributed in the size range of <0.1 mm, while Ni(OH)2 / NF and Ni(OH)2 / SCE exhibit larger sizes, with 93% and 100% of the bubbles distributed in the size range of >0.2 mm, respectively.

[0073] The above results demonstrate that the three-dimensional porous array carbon electrode can promptly provide reactants at industrial-grade current densities and facilitate the timely removal of numerous small bubbles, ensuring the efficient operation of the gas-generating reaction. To quantitatively analyze the activity differences between different electrodes, Ni was measured using CV curves in a 1 M KOH electrolyte. 2+ / Ni 3+ Oxidation peaks were used to assess the active site density, and the results showed that the site density of Ni(OH)2 / ACE was as high as 6.6 × 10⁻⁶. 18 site / cm 2 It is 6 times that of Ni(OH)2 / NF. Figure 9 ).

[0074] The UOR performance of the catalytic electrode was tested using a three-electrode system in a 1 M KOH electrolyte containing 0.33 M urea.

[0075] like Figure 10 As shown, the Ni(OH)2 / ACE of Example 1 exhibits high activity, reaching 100 mA cm⁻¹ at low voltages of 1.340 V and 1.360 V. −2 and 1000 mA cm −2 The current density of Ni(OH)2 / ACE is significantly better than that of other electrodes. Furthermore, the current density of Ni(OH)2 / ACE is within the range of 0–1000 mA cm⁻¹. −2 The potential increases sharply over a wide current density range, indicating the crucial role of the porous array carbon structure in achieving high gas-producing reaction rates. Furthermore, the Δ... E / Δlog| j The ratio remains low even as current density increases, up to 1000 mA cm⁻¹. −2 At current density, it is only 0.03 Vdec −1 The results indicate that the arrayed carbon electrode has strong mass transfer capability at high current densities; however, the ratios of Ni(OH)2 / NF in Comparative Example 1 and Ni(OH)2 / SCE in Comparative Example 2 increase sharply with increasing current density, indicating that their mass transfer capabilities are poor. Furthermore, Ni(OH)2 / ACE also exhibits high stability at 100 mA cm⁻¹.−2 The potential decay is about 1.2% after 100 hours of continuous operation. The NiFe(OH) x / ACE and Ru / ACE array carbon electrodes also have excellent large current density performance for OER and HER to produce gas.

[0076] As Figure 11 shown, the NiFe(OH) x / ACE and Ru / ACE achieve a large current density of 1000 mA cm −2 , only requiring an overpotential of 250 mV and 87 mV, and also have a fast mass transfer process at an industrial level of large current density.

[0077] Considering the excellent catalytic performance of the three-dimensional array carbon electrode, a two-electrode electrolysis system with Ni(OH)2 / ACE as the anode and Ru / ACE as the cathode was constructed, and the performance of the Ni(OH)2 / ACE||Ru / ACE electrolytic cell for electrolysis of urea and water was tested in 1 M KOH electrolyte with and without 0.33 M urea, as shown in Figure 12 The polarization curve results show that for the electrolysis of urea, the Ni(OH)2 / ACE||Ru / ACE electrolytic cell requires only 1.412 V and 1.554 V of cell voltage to achieve a current density of 100 mA cm −2 and 1000 mA cm −2 , which is significantly lower than the voltage required for the electrolysis of water at the same current density (1.639 V and 1.972 V). At an industrial level of large current density of 1000 mA cm −2 , the urea-assisted water electrolysis system can reduce the voltage by about 420 mV, which indicates that UOR is a very promising anode alternative reaction that can replace OER to produce hydrogen on a large scale and treat wastewater rich in urea, thereby realizing a more energy-saving and efficient industrial level of mixed water electrolysis hydrogen production system.

[0078] Example 4:

[0079] The difference between this example and Example 1 is that in step (1), the temperature of the hydrothermal reaction is different, and in this example, the three-dimensional porous array carbon electrode Ni(OH)2 / ACE is obtained by hydrothermal self-assembly at 180 °C for 12 hours.

[0080] Example 5:

[0081] The difference between this example and Example 1 is that in step (1), the time of the hydrothermal reaction is different, and in this example, the three-dimensional porous array carbon electrode Ni(OH)2 / ACE is obtained by hydrothermal self-assembly at 120 °C for 6 hours.

[0082] As Figure 13As shown, the scanning electron microscope images show that the carbon electrode prepared in Example 4 has a disordered porous structure with a pore size of about 1 μm; the carbon electrode prepared in Example 5 has a vertically arranged porous array structure with a pore size of about 20 μm. The mercury intrusion test results show that the smaller the pore size, the larger the pore area, and the smaller the porosity. The pore area of the carbon in Example 4 is as high as 247.9 m 2 g −1 As shown, the scanning electron microscope images show that the carbon electrode prepared in Example 4 has a disordered porous structure with a pore size of about 1 μm; the carbon electrode prepared in Example 5 has a vertically arranged porous array structure with a pore size of about 20 μm. The mercury intrusion test results show that the smaller the pore size, the larger the pore area, and the smaller the porosity. The pore area of the carbon in Example 4 is as high as 247.9 m Figure 14

[0083] Figure 15 The polarization curves further reveal the relationship between the pore structure and the UOR performance, and the results show that the best sample, Example 1, exhibits high activity and efficient mass transfer at a large current density, while the activity of Example 5 is lower due to the small pore area resulting in a small number of active sites loaded, which makes the activity poor; Example 4 has poor mass transfer at 1000 mA cm −2 E j −1 Therefore, both a large pore area and an ordered porous structure can improve the catalytic performance.​​​​

Claims

1. A method for fabricating a three-dimensional porous array carbon electrode, characterized in that, Includes the following steps: (1) The GONR solution was ultrasonically treated and then transferred to a high-pressure reactor for hydrothermal self-assembly reaction to obtain a hydrogel; (2) Cut the hydrogel into thin slices, place them on a copper block pre-cooled with liquid nitrogen for ice template treatment, freeze dry, and finally anneal to obtain a three-dimensional array carbon film electrode substrate. (3) An active material is deposited on the three-dimensional array carbon film electrode substrate by electrodeposition to obtain the three-dimensional porous array carbon electrode. The three-dimensional porous array carbon electrode includes a multi-scale pore structure composed of micron-pores and nanopores, and its specific surface area is not less than 200 m². 2 g 1 The hole area is not less than 50 m² 2 g 1 The three-dimensional porous array carbon electrode has a roughness of not less than 2800, and can provide 1000 mA cm⁻¹ at a low potential of 1.360 V in the urea oxidation reaction. 2 High current density.

2. The preparation method according to claim 1, characterized in that, In step (3), the active substance is Ni(OH)2, Ru, or NiFe(OH). x At least one of them.

3. The preparation method according to claim 1, characterized in that, In step (3), the electrodeposition employs a standard three-electrode system, with a three-dimensional array carbon film electrode substrate, an Ag / AgCl electrode, and a graphite rod serving as the working electrode, reference electrode, and counter electrode, respectively. The electrodeposition is carried out in the electrolyte. 0.4 V ~ A three-dimensional porous array carbon electrode was obtained by electrodeposition at a constant potential of 1.2 V vs. Ag / AgCl for 5-15 min followed by washing.

4. The preparation method according to claim 1, characterized in that, In step (2), the freeze-drying temperature is -40 to -60 °C, and the time is 1-8 h; The annealing process is carried out in an inert atmosphere, the annealing temperature is 700-900 ℃, and the annealing time is 0.5-2 h.

5. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal self-assembly reaction is 120-180 ℃ and the time is 6-12 h.

6. The preparation method according to claim 1, characterized in that, The water droplet contact angle of the three-dimensional porous array carbon electrode is no higher than 10°, and the bubble contact angle is no lower than 160°.

7. The application of a three-dimensional porous array carbon electrode prepared by any one of claims 1 to 6 in hydrogen production by water electrolysis.

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