A NiSe2 / VN-C / C bifunctional electrocatalytic material and its preparation method and application

Abstract

The invention discloses a NiSe2 / VN-C / C bifunctional electrocatalytic material and its preparation method and application. The preparation method comprises: taking a vanadium source and a nitrogen source, placing them in an agate mortar and grinding them to mix them evenly, transferring the mixed powder to a porcelain boat, laying it flat, and placing it in a tube furnace, and keeping it at 700-900°C under an argon atmosphere for 2 hours to obtain black VN powder; taking a nickel source and selenium powder according to a molar ratio of nickel source to selenium source of 1:(1-2), taking VN according to a molar ratio of nickel source to vanadium source of 1:(0.8-2), and adding them to ethyl acetate. The method comprises the following steps: adding the pretreated C / C composite material to a diol solution and stirring uniformly to obtain a mixed solution; transferring the mixed solution to a polytetrafluoroethylene liner of an autoclave, placing the pretreated C / C composite material to ensure that the composite material is immersed in the solution, and sealing the autoclave; finally, placing the autoclave in an electric blast drying oven for a solvent thermal reaction; removing the autoclave from the autoclave after washing, and then sealing and drying the autoclave at room temperature to obtain a NiSe2 / VN-C / C sample; and the prepared NiSe2 / VN-C / C bifunctional electrocatalytic material has good electrocatalytic performance and stability, a simple preparation method, and controllable morphology.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials and relates to electrocatalytic materials, and specifically relates to a NiSe2 / VN-C / C bifunctional electrocatalytic material and a preparation method and application thereof. Background Art

[0002] With the growing concern about energy and environmental issues, the development of clean and renewable energy has become increasingly urgent. Hydrogen is one of the most promising energy sources due to its significant energy density per unit weight, abundant reserves, and clean properties. In the future, hydrogen may reduce or even replace traditional fossil fuels such as crude oil, natural gas, and coal. The electrocatalytic hydrogen evolution reaction (HER) is of particular interest as a production pathway. The energy barrier and overpotential of HER can be reduced by using efficient and stable electrocatalysts, which will significantly improve the energy conversion efficiency of HER [Gautam, S. Sk, U. Pal, Recent advances in solution-assisted synthesis of transition metal chalcogenides for photo-electrocatalytic hydrogen evolution, Phys. Chem. Chem. Phys. 24 (2022) 20638–20673]. Platinum (Pt) is widely considered to be the most efficient and durable catalyst for HER in acidic and alkaline environments. However, the scarcity and high cost of Pt-based catalysts have greatly limited their practical applications. Therefore, there is an urgent need to explore cost-effective and efficient noble metal-free electrocatalysts as viable alternatives. In recent years, various transition metal oxides, hydroxides, nitrides, phosphides, sulfides and selenides have been widely studied to find electrocatalysts to replace precious metal-based HER catalysts. Vanadium nitride (VN) is a typical transition metal nitride that not only has the unique properties of transition metal nitrides, such as metallicity and Pt-like electronic structure, but also has unique physical and chemical properties, such as high melting point and corrosion resistance [E. Yuan, M. Zhou, G. Shi, P. Jian, X. Hou, Ultralow-loading single-atom cobalt on graphitic carbon nitrogen with robust Co-N pairs for aerobic cyclohexane oxidation, Nano Res. 15 (2022) 8791–8803]. It is an interstitial compound in which nitrogen atoms are infiltrated into the parent metal V, corresponding to the contraction of the density of states (DOS) of the parent metal's d band near the Fermi level. The presence of nitrogen ions gives it unique electronic and bonding characteristics, resulting in unique physical and chemical properties, such as excellent electrochemical activity.The main challenge for hydrogen adsorption on VN is its insufficient electron density [Yang, K. Shen, Y. Liu, Y. Tan, X. Zhao, J. Wu, X. Niu, F. Ran, Novel hybrid nanoparticles of vanadium nitride / porous carbon as an anode material forsymmetrical supercapacitor, Nano Micro Lett 9 (2017) 1–15].

[0003] Transition metal dichalcogenides (TMDs) have attracted much attention due to their low price, abundant reserves, and high electrocatalytic HER efficiency [Dong, T. Zhang, X. Feng, Interface-Assisted Synthesis of 2DMaterials: Trend and Challenges, Chem. Rev. 118 (2018) 6189–6235]. NiSe2, as a new type of transition metal chalcogenide, has gained a high reputation in the field of electrocatalysis due to its high conductivity, low bandgap, high chemical stability and low cost [Ramakrishnan, S. Jo, N. Pitipuech, J. Sohn, Bifunctionality behavior of phase controlled nickel selenides in alkaline water electrolysis application, Electrochim. Acta 354 (2020), 136742]. The 3d orbital of Se may be involved in bonding with metal atoms because its energy level is close to that of 3s and 3p orbitals. This electronic structure leads to a higher metallicity in transition metal selenides, which is conducive to the transport and reaction of electrons. In addition, transition metal selenides have the advantages of simple preparation, good catalytic activity and good stability, making them ideal candidates for electrochemical water splitting.

[0004] Combining two or more heterogeneous materials to achieve complementary advantages and improve structural properties is considered an effective method to improve catalytic activity. However, existing heterogeneous electrocatalysts still have defects such as limited stability, easy poisoning and deactivation after long-term use, special requirements for pH value, temperature or electrolyte concentration, and limited application range. It is worth noting that HER electrocatalysts perform well in acidic electrolytes, while OER electrocatalysts work better under alkaline conditions. The pH mismatch between OER and HER composite electrocatalysts will inevitably lead to poor water splitting performance. Although HER and OER bifunctional electrocatalysts have been developed to simplify water splitting systems and reduce costs, they usually exhibit excellent HER activity and relatively poor OER catalytic activity, and vice versa. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a NiSe2 / VN-C / C bifunctional electrocatalytic material with good electrocatalytic performance and long-term stability in a strong alkaline environment, as well as a preparation method and application thereof. The preparation method is simple and the product morphology is controllable.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a NiSe2 / VN-C / C bifunctional electrocatalytic material comprises the following steps:

[0008] Step 1: Grind the raw materials in an agate mortar at a molar ratio of vanadium source to nitrogen source of 1:(4-7) to mix them evenly. Transfer the mixed powder to a porcelain boat, lay it flat, and place it in a tube furnace. Under an argon atmosphere, heat it from room temperature to 700-900°C and keep it warm for 1-4 hours. After the process is completed, cool it to room temperature to obtain black VN powder.

[0009] Step 2: Take a nickel source and selenium powder at a molar ratio of 1:(1-2) of nickel source to selenium powder, and take the VN prepared in step 1 at a molar ratio of 1:(0.8-2) of nickel source to vanadium source, add the nickel source, selenium powder and VN together to the ethylene glycol solution, and stir to obtain a mixed solution;

[0010] Step three, transfer the mixed solution to the polytetrafluoroethylene lining of the high-pressure reactor, put in the pretreated C / C composite material, ensure that it is immersed in the solution, and seal it well. Finally, place the high-pressure autoclave in an electric blast drying oven, set the temperature parameters to 100-170 ° C, and the insulation time to 10-16 hours. After the reaction is completed and cooled to room temperature, take it out, wash it, seal it and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

[0011] The present invention also has the following technical features:

[0012] Preferably, the vanadium source in step 1 includes any one of vanadium trichloride, vanadium acetylacetonate and vanadium sulfate.

[0013] Preferably, the nitrogen source in step 1 comprises any one of urea, dicyandiamide and melamine.

[0014] Preferably, the heating rate of the tubular furnace during the calcination process in step 1 is 2-10° C. / min.

[0015] Preferably, the nickel source in step 2 includes any one of nickel dichloride, nickel acetylacetonate and nickel nitrate.

[0016] Preferably, the pretreatment method of the C / C composite material described in step 3 includes: ultrasonically cleaning the carbon / carbon matrix with ultrapure water and ethanol alternately for 10 minutes each time, repeated 3 times, and finally placing it in a culture dish and drying it in an electric blast drying oven at 50°C for 6 hours.

[0017] Preferably, the filling ratio of the polytetrafluoroethylene liner in step three is 50%.

[0018] Preferably, the washing in step 3 is performed by alternately rinsing with ultrapure water and ethanol for 3 to 5 times.

[0019] The present invention also protects a NiSe2 / VN-C / C bifunctional electrocatalytic material prepared by the method as described above and its use as an electrocatalyst for electrolysis of water to produce hydrogen, electrolysis of water to produce oxygen or full water splitting in a strong alkaline environment.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention uses a simple two-step method to grow uniformly distributed VN-core tetrahedral NiSe2 / VN on a carbon / carbon matrix to obtain a NiSe2 / VN-C / C bifunctional electrocatalytic material with multiple exposed active sites and a large specific surface area. VN, which has high intrinsic activity but insufficient d-band electron density, is composited with highly metallic NiSe2 to form a heterogeneous structure, which is beneficial for optimizing the electronic structure and promoting charge transfer, thereby enhancing the electrocatalytic hydrogen evolution reaction. At the same time, a low-density C / C composite material is used as a self-supporting substrate to effectively reduce the serious aggregation, poor conductivity, and numerous inactive basal planes of the catalytically active material, thereby promoting material transfer and improving performance. The material exhibits good electrocatalytic performance in hydrogen production, oxygen production, or complete water splitting reactions by electrolysis of water. At a current density of 100 in an alkaline solution, the overpotential required for electrocatalytic hydrogen evolution (HER) is only 238 mV.

[0022] The present invention adopts an atmosphere free of ammonia and nitrogen, has the advantages of simple technology, controllable process, environmental friendliness and safety, and good product morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD pattern of NiSe2 / VN-C / C prepared in Example 1;

[0024] Figure 2 This is the SEM image of NiSe2 / VN-C / C prepared in Example 1;

[0025] Figure 3 This is the LSV curve of the electrocatalytic hydrogen evolution of NiSe2 / VN-C / C prepared in Example 1. DETAILED DESCRIPTION

[0026] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0027] Example 1:

[0028] Step 1: Weigh 174.13 mg of vanadium trichloride (VCl3) and 294.28 mg of dicyandiamide to ensure that the molar ratio of the V source to the nitrogen source is 1:7. Place the weighed raw materials in an agate mortar and grind them for 30 minutes to mix them evenly. Transfer the mixed powder to a porcelain boat and flatten it. Use a tube furnace at 900 ° C. Under an argon atmosphere, keep warm for 2 hours at a heating rate of 10 ° C / min. After the program is completed and cooled to room temperature, the resulting black VN powder is ground using an agate mortar for 10 minutes and collected;

[0029] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 minutes each time, and repeated 3 times. Finally, the carbon / carbon substrate was placed in a culture dish and dried in an electric blast drying oven at 50°C for 6 hours for later use;

[0030] Weigh 237.69 mg of nickel dichloride hexahydrate (NiCl2·6H2O) and 79 mg of selenium powder to ensure that the molar ratio of nickel to Se source is 1:1; add the weighed nickel source and selenium powder and 52 mg of VN obtained in step 1 (to ensure the molar ratio of Ni source to VN is 5:4) to 25 mL of ethylene glycol solution and stir magnetically for 4 h to obtain a mixed solution;

[0031] Step 3: Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined autoclave, place a piece of treated C / C composite material, ensure that it is immersed in the solution, seal it well, and keep the volume filling ratio controlled at 50%. Finally, place the autoclave in an electric blast drying oven, set the temperature parameter to 120 ° C, and the insulation time to 14 h. After the reaction is completed and cooled to room temperature, take out the C / C, rinse it alternately with ultrapure water and ethanol three times, seal it and dry it at room temperature to obtain a NiSe2 / VN-C / C sample;

[0032] Figure 1The SEM photo of NiSe2 / VN-C / C prepared in Example 1; Figure 1 It can be seen that tetrahedral NiSe2 / VN with prefabricated VN as the core is grown on the carbon / carbon matrix, which is evenly distributed and has a large specific surface area.

[0033] Figure 2 The XRD pattern of NiSe2 / VN-C / C prepared in Example 1 is as follows; Figure 2 As shown, the C peak at 26.3° is attributed to the matrix; the peaks at 25.858°, 29.945°, 33.579°, 36.893°, 42.861°, and 50.737° are attributed to the (1 1 1), (2 0 0), (2 1 0), (2 1 1), (2 2 0), and (3 1 1) crystal planes of NiSe2 (JCPDS card number 88-1711); and the peaks at 37.7°, 43.8°, 63.7°, and 76.5° are attributed to the (111), (200), (220), and (311) crystal planes of VN (JCPDS card number 35-0768).

[0034] In a standard three-electrode system, the electrocatalytic performance of NiSe2 / VN-C / C was tested in a 1 M KOH electrolyte solution. Figure 3 To evaluate the catalytic activity of the prepared samples, the -1 Linear sweep voltammetry (LSV) tests showed that the electrocatalytic hydrogen evolution performance required an overpotential of 238 mV at a current density of 100.

[0035] In order to evaluate the electrocatalytic oxygen evolution performance of the prepared samples, the -1 Linear sweep voltammetry (LSV) tests were conducted, and the electrocatalytic hydrogen evolution required overpotentials of 335, 428, and 545 mV at current densities of 100, 500, and 1000, respectively. Similarly, in order to evaluate the electrocatalytic water splitting performance of the prepared samples, the overpotentials were 5 mV·s -1 Linear sweep voltammetry (LSV) tests were performed, and complete water splitting required only a voltage of 1.853 V at a current density of 100.

[0036] Example 2

[0037] Step 1: Weigh 348.3 mg of vanadium acetylacetonate (V(CH3COCHCOCH3)3)3 and 1135.1 mg of melamine to ensure that the molar ratio of the V source to the nitrogen source is 1:6. Place the weighed raw materials in an agate mortar and grind them for 30 minutes to mix them evenly. Transfer the mixed powder to a porcelain boat and flatten it. Use a tube furnace at 800°C under an argon atmosphere for 2 hours at a heating rate of 10°C / min. After the program is completed and cooled to room temperature, the resulting black VN powder is ground using an agate mortar for 10 minutes and collected.

[0038] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 minutes each time, and repeated 3 times. Finally, the carbon / carbon substrate was placed in a culture dish and dried in an electric blast drying oven at 50°C for 6 hours for later use;

[0039] Weigh 237.7 mg of nickel dichloride hexahydrate (NiCl2·6H2O) and 79 mg of selenium powder to ensure that the molar ratio of nickel to Se source is 1:1; add the weighed nickel source and selenium powder and 65 mg of VN obtained in step 1 (ensuring that the molar ratio of Ni source to VN is 1:1) to 25 mL of ethylene glycol solution and stir magnetically for 4 h to obtain a mixed solution;

[0040] Step 3. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined high-pressure reactor, put in a piece of treated C / C composite material, ensure that it is immersed in the solution, seal it well, and keep the volume filling ratio controlled at 50%. Finally, place the autoclave in an electric blast drying oven, set the temperature parameter to 140 ° C, and the insulation time to 14 h. After the reaction is completed and cooled to room temperature, take out the C / C, rinse it alternately with ultrapure water and ethanol 4 times, seal and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

[0041] Example 3:

[0042] Step 1: Weigh 236 mg of vanadium trichloride (VCl3) and 945.9 mg of melamine, with a molar ratio of V source to nitrogen source of 1:5. Place the weighed raw materials in an agate mortar and grind for 30 minutes to mix them evenly. Transfer the mixed powder to a porcelain boat and flatten it. Use a tube furnace at 800 ° C. Under an argon atmosphere, keep warm for 2 hours at a heating rate of 10 ° C / min. After the program is completed and cooled to room temperature, the resulting black VN powder is ground using an agate mortar for 10 minutes and collected;

[0043] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 minutes each time, and repeated 3 times. Finally, the carbon / carbon substrate was placed in a culture dish and dried in an electric blast drying oven at 50°C for 6 hours for later use;

[0044] Weigh 256.9 mg of nickel acetylacetonate (Ni(CH3COCHCOCH3)2); weigh 118.5 mg of selenium powder, ensuring that the molar ratio of nickel and Se source is 2:3; add the weighed nickel source and selenium powder and 97.4 mg of VN obtained in step 1 (ensuring the molar ratio of Ni source to VN is 2:3) to 25 mL of ethylene glycol solution, and stir magnetically for 4 h to obtain a mixed solution;

[0045] Step 3. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined high-pressure reactor, put in a piece of treated C / C composite material, ensure that it is immersed in the solution, seal it well, and keep the volume filling ratio controlled at 50%. Finally, place the autoclave in an electric blast drying oven, set the temperature parameters to 150 ° C, and the insulation time to 14 h. After the reaction is completed and cooled to room temperature, take out the C / C, rinse it alternately with ultrapure water and ethanol several times, seal and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

[0046] Example 4:

[0047] Step 1: Weigh 91 mg of vanadium sulfate and 80.06 mg of urea, with a molar ratio of V source to nitrogen source of 1:4. Place the weighed raw materials in an agate mortar and grind them for 30 minutes to mix them evenly. Transfer the mixed powder to a porcelain boat and flatten it. Use a tube furnace at 700°C under an argon atmosphere for 4 hours at a heating rate of 5°C / min. After the program is completed and cooled to room temperature, the resulting black VN powder is ground using an agate mortar for 10 minutes and collected.

[0048] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 minutes each time, and repeated 3 times. Finally, the carbon / carbon substrate was placed in a culture dish and dried in an electric blast drying oven at 50°C for 6 hours for later use;

[0049] Weigh 217.5 mg of nickel nitrate; weigh 118.5 mg of selenium powder, ensuring that the molar ratio of nickel and Se source is 1:2; add the weighed nickel source and selenium powder and 97.4 mg of VN obtained in step 1 (ensuring the molar ratio of Ni source to VN is 1:2) to 25 mL of ethylene glycol solution and stir magnetically for 4 h to obtain a mixed solution;

[0050] Step 3. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined high-pressure reactor, put in a piece of treated C / C composite material, ensure that it is immersed in the solution, seal it well, and keep the volume filling ratio controlled at 50%. Finally, place the autoclave in an electric blast drying oven, set the temperature parameter to 100 ° C, and the insulation time to 16 h. After the reaction is completed and cooled to room temperature, take out the C / C, rinse it alternately with ultrapure water and ethanol several times, seal and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

[0051] Example 5:

[0052] Step 1: Weigh 236 mg of vanadium trichloride (VCl3) and 945.9 mg of melamine, with a molar ratio of V source to nitrogen source of 1:5. Place the weighed raw materials in an agate mortar and grind them for 30 minutes to mix them evenly. Transfer the mixed powder to a porcelain boat and flatten it. Use a tube furnace at 800°C under an argon atmosphere for 1 hour at a heating rate of 2°C / min. After the procedure is completed and cooled to room temperature, the resulting black VN powder is ground using an agate mortar for 10 minutes and collected.

[0053] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 minutes each time, and repeated 3 times. Finally, the carbon / carbon substrate was placed in a culture dish and dried in an electric blast drying oven at 50°C for 6 hours for later use;

[0054] Weigh 256.9 mg of nickel acetylacetonate (Ni(CH3COCHCOCH3)2); weigh 118.5 mg of selenium powder, ensuring that the molar ratio of nickel and Se source is 2:3; add the weighed nickel source and selenium powder and 97.4 mg of VN obtained in step 1 (ensuring the molar ratio of Ni source to VN is 2:3) to 25 mL of ethylene glycol solution, and stir magnetically for 4 h to obtain a mixed solution;

[0055] Step 3. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined high-pressure reactor, put in a piece of treated C / C composite material, ensure that it is immersed in the solution, seal it well, and keep the volume filling ratio controlled at 50%. Finally, place the autoclave in an electric blast drying oven, set the temperature parameters to 170 ° C, and the insulation time to 10 h. After the reaction is completed and cooled to room temperature, take out the C / C, rinse it alternately with ultrapure water and ethanol several times, seal and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

[0056] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a NiSe2 / VN-C / C bifunctional electrocatalytic material, characterized in that: The following steps are involved: Step 1: Grind the raw materials in an agate mortar at a molar ratio of vanadium source to nitrogen source of 1:5 to mix them evenly. Transfer the mixed powder to a porcelain boat, lay it flat, and place it in a tube furnace. Under an argon atmosphere, heat it from room temperature to 700-900 ° C, keep it warm for 1-4 hours, and cool it to room temperature after the procedure is completed to obtain black VN powder; the nitrogen source is melamine; Step 2: Take nickel source and selenium powder at a molar ratio of nickel source to selenium powder of 1:(1-2), take VN prepared in step 1 at a molar ratio of nickel source to vanadium source of 1:(0.8-2), add the nickel source, selenium powder and VN together to the ethylene glycol solution, and stir to obtain a mixed solution; Step 3: Transfer the mixed solution to the polytetrafluoroethylene liner of the autoclave, put in the pretreated C / C composite material, ensure that it is immersed in the solution, and seal it well. Finally, place the autoclave in an electric blast drying oven, set the temperature parameters to 100~170 °C, and the insulation time to 10~16 h. After the reaction is completed and cooled to room temperature, take it out, wash it, seal it and dry it at room temperature to obtain the NiSe2 / VN-C / C sample.

2. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The vanadium source in step 1 includes any one of vanadium trichloride, vanadium acetylacetonate and vanadium sulfate.

3. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The heating rate of the tubular furnace during the calcination process in step 1 is 2-10 °C / min.

4. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The nickel source in step 2 includes any one of nickel dichloride, nickel acetylacetonate and nickel nitrate.

5. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The pretreatment method of the C / C composite material described in step 3 includes: ultrasonic cleaning the carbon / carbon matrix with ultrapure water and ethanol alternately for 10 minutes each time, repeated 3 times, and finally placing it in a culture dish and drying it in an electric blast drying oven at 50 °C for 6 hours.

6. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The filling ratio of the polytetrafluoroethylene liner described in step 3 is 50%.

7. The method for preparing the NiSe2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The washing described in step 3 is to rinse alternately with ultrapure water and ethanol 3 to 5 times.

8. A NiSe2 / VN-C / C bifunctional electrocatalytic material prepared by the method according to any one of claims 1 to 7.

9. Use of the Ni3S2 / VN-C / C bifunctional electrocatalytic material as claimed in claim 8 as an electrocatalyst for hydrogen production, oxygen production or complete water splitting in a strong alkaline environment.

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