Claims:1. A three-dimensional electrode for seawater electrolysis, characterized in that, the electrode comprises nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam,
wherein the three-dimensional electrode favours high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

2. The three-dimensional electrode as claimed in claim 1, wherein the electrode is a Nickel-iron (oxy) hydroxide based three-dimensional electrode.

3. The three-dimensional electrode as claimed in claims 1 and 2, wherein the electrode is a Sodium sulphide induced iron (oxy) hydroxide based three-dimensional electrode.

4. A Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode,
wherein the three-dimensional electrode favours high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

5. The electrode as claimed in claim 4, wherein the electrode performs Oxygen evolution reaction (OER) efficiently in two-electrode electrolyzer setup up to 2.5 V without evolution of chlorine ions.

6. The electrode as claimed in claim 4, wherein the electrode indicates an excellent activity with 400 mA/cm2 current density at a potential 1.6 V.

7. The electrode as claimed in claim 4, wherein the electrode is active at a temperature range between 25 ºC to 70 ºC and in all basic pH conditions.

8. A process for preparation of Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode, wherein the process comprises steps of:
I: Controlled precursor mixing:
a) separately dissolving Ferric nitrate nonahydrate and Sodium Sulfide in De- ionized water, forming solution A and solution B respectively;
b) adding solution B in solution A dropwise via continuous stirring till the appearance of black turbidity in the reaction mixture;
II: Catalyst formation via hydrothermal procedure:
c) immersing pre-processed Ni foam into the reaction mixture of step (b) and transferring it into a Teflon lined autoclave and sealed tightly;
d) keeping the auto clave in an oven at a temperature range between 70 ⁰C to 100 ⁰C for 18 hours followed by cooling at room temperature to obtain black colored Ni foam in the solution;
e) removing black colored Ni foam obtained in step (d) from the solution, followed by washing several times with the de-ionized water and drying at room temperature overnight, to obtain Sodium Sulphide induced Nickel-iron (oxy) hydroxide-based 3D electrode (S-NiFeOOH);
III: Electrochemical activation of the catalyst on the electrode:
f) activating the obtained electrode electrochemically.

9. The process as claimed in claim 8, wherein in step (c), the pre-processing of Ni foam comprises the steps of:
sonication of commercially obtained Ni foam with HCl for 15 minutes to remove surface oxide or any other greasing materials, followed by consecutive washing with De-ionized water and ethanol; and drying the washed Ni foam.

10. The process as claimed in claim 8, wherein in step (d), the auto clave is kept in an oven at 80 ⁰C for 18 hours.
, Description:FIELD OF THE INVENTION:

The present invention relates to electrodes for seawater electrolysis. Particularly, the invention relates to a three-dimensional electrode for sustainable electrolysis of direct sea water/low grade water/ground water and process for preparation thereof. More particularly, the invention relates to three-dimensional electrode based on the Ni foam wherein nanometallic S-doped metal oxyhydroxides flakes have been grown on Ni foam. The invention is about product i.e. catalyst and subsequent electrode for electrocatalysis. The three-dimensional electrode of the present invention possess specificity for selective Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER) by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

BACKGROUND OF THE INVENTION:

The rising global demand of energy calls for environmentally friendly, efficient, and economical energy conversion and storage technologies. Electrochemical water-splitting into hydrogen and oxygen is a promising technology to effectively exploit renewable energy from harvest to redistribution. Seawater electrolysis is for both hydrogen generation and seawater desalination, which however requires highly active and robust oxygen evolution reaction (OER) catalysts that can sustain seawater splitting without chloride corrosion. The key catalytic challenge for seawater electrolysis consists in the competition between the Chlorine evolution reaction (CER) and the Oxygen evolution reaction (OER), therefore the electrocatalysts are unable to sustain against Chloride corrosion.

The several catalysts are reported in the known literature for broad range of catalytic efficiency, the electrocatalytic water-splitting of sea or low-grade water possessing various impurities are still under considerations. The reason behind this is the degradation of the electrode and unwanted side reactions such as chlorine evolution reactions (CER).
In the last decade, various researchers have started working in this direction of sea water electrolysis. Many efforts have been made in the prior arts; some are as follows:

Sören Dresp et.al., Direct Electrolytic Splitting of Seawater – Opportunities and Challenges, DOI: 10.1021/acsenergylett.9b00220, discloses that in combination with a hydrogen fuel cell, a reversible seawater electrolysis scheme is possible that holds promise for the storage of surplus electricity in form of molecular hydrogen and, more as a collateral process, purified water is formed during the fuel cell reaction. This prior art develops and suggests a process concept for a sustained fresh water supply based on the combination of RO water purification and direct seawater electrolysis. Offshore wind parks and solar energy rich coastal desert regions would benefit the most from this combined process technology, where molecular hydrogen is transformed back into electricity and water. However, the direct electrolytic splitting is unable to ripple the chloride evolution reaction (CER).

Wenming Tong et.al. Electrolysis of low grade and saline surface water DOI: 10.1038/s41560-020-0550-8, discloses an alkaline water electrolyser, which operates as a two-compartment cell separated by a porous diaphragm that allows hydroxyl ion (OH-) migration while preventing gas crossover. A liquid alkaline electrolyte is pumped around both sides of the cell and water is reduced at the cathode into H2 and OH-. The unsupported NiFe layered double hydroxide (LDH) catalyst in a membrane electrode assembly (MEA) experimentally confirmed the concept of the criterion, by demonstrating current densities up to 290 mA cm-2 at under ~480 mV overpotential, which is close to what is required for medium or large size electrolysers. However, the material used in electrolysis of low grade and saline surface water is unable to generate high current density at very low voltage value.

None of these prior art documents are still capable of utilizing pure sea water for hydrogen and oxygen generation with a very high current density at a lower rate of voltage. Further, the electrocatalysts in the known prior arts are unable to sustain and carry out electrolysis of sea water since Chlorine evolution reaction (CER) competes with the Oxygen evolution reaction (OER). Therefore, a catalyst which can tolerate or repel majorly present chloride ions from the surface of the electrode is required for successful development of sea or low-grade water electrolyzer.

Therefore, there is need of careful design of anodes and electrolytes which can fully solve the chloride corrosion problem and allow direct splitting of seawater into renewable fuels without desalination. The present invention discloses direct sustainable electrolysis of chloride containing water at high current density. The present invention provides nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam based three-dimensional electrode which utilizes a catalyst system that is selective towards Oxygen evolution reaction (OER) compared to that of the Chlorine evolution reaction (CER) and possibly the in-situ formed anionic layer stops the transport of chloride anion towards the electrode surface thus, the product became viable for sustainable sea water electrolysis. The three-dimensional electrode of present invention is suitable for direct electrolysis of chloride containing water. The catalysts are able to generate high current density over a long period of time. These can be synthesized in a large scale in an economical manner without using any sophisticated reaction set up.

OBJECTS OF THE INVENTION:

The principal object of present invention is to provide a three-dimensional electrode for seawater electrolysis.

Another object of the invention is to provide a three-dimensional electrode for seawater electrolysis comprising nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam, for selective Oxygen evolution reaction (OER) over Chlorine evolution reaction (CER) activity.

Another object of the invention is to provide a novel catalyst which is able to generate high current density at low potential over a long period of time and can be synthesized in a large scale in an economical manner without any sophisticated reaction set up.

Another object of the invention is to provide Sodium Sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode that enhance Oxygen evolution reaction (OER) activity and minimizes Chlorine evolution reaction (CER) activity, by forming the in-situ anionic layer on it which repel the chloride anions from the surface of electrode.

Another object of the invention is to provide a novel procedure to fabricate a low-cost three-dimensional electrode (S-NiFeOOH).

Yet another object of the invention is to provide a process for preparation of three-dimensional electrode Sodium Sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) having high Oxygen evolution reaction (OER) activity and provides corrosion resistance to chloride anions in seawater.

The present invention is about product i.e. catalyst and subsequent electrode for electrocatalysis and the process for preparation thereof.

SUMMARY OF THE INVENTION:

Accordingly, the present invention provides and discloses a three-dimensional electrode for seawater electrolysis. More particularly, the invention relates to a Nickel-iron (oxy) hydroxide based three-dimensional electrode for seawater electrolysis. The Nickel-iron (oxy) hydroxide based electrode favors the high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER) by forming an in-situ anionic layer on it which repel the chloride anions from the surface of electrode.

The preset invention provides a three-dimensional electrode possessing an excellent activity with higher current density at a very low value of the potential. The electrode is capable of sustainably performing the electrolysis of chloride containing water for a very long period.

The present invention discloses a novel catalyst composition and a novel procedure to fabricate the 3D electrode.

In one aspect, the present invention discloses a three-dimensional electrode for seawater electrolysis, characterized in that, the electrode comprises nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam,
wherein the three-dimensional electrode favours high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

The said three-dimensional electrode is a Nickel-iron (oxy) hydroxide based three-dimensional electrode.

The said three-dimensional electrode is a Sodium sulphide induced iron (oxy) hydroxide based three-dimensional electrode.

In another aspect, the present invention discloses a Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode,
wherein the three-dimensional electrode favours high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

The said electrode performs Oxygen evolution reaction (OER) efficiently in two-electrode electrolyzer setup up to 2.5 V without evolution of chlorine ions.
The said electrode indicates an excellent activity with 400 mA/cm2 current density at a potential 1.6 V.

The said electrode is active at a temperature range between 25ºC to 70ºC and in all basic pH conditions.

In another aspect, the present invention provides a process for preparation of Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode, wherein the process comprises steps of:
I: Controlled precursor mixing:
a) separately dissolving Ferric nitrate nonahydrate and Sodium Sulfide in De- ionized water, forming solution A and solution B respectively;
b) adding solution B in solution A dropwise via continuous stirring till the appearance of black turbidity in the reaction mixture;
II: Catalyst formation via hydrothermal procedure:
c) immersing pre-processed Ni foam into the reaction mixture of step (b) and transferring it into a Teflon lined autoclave and sealed tightly;
d) keeping the auto clave in an oven at a temperature range between 70⁰C to 100⁰C for 18 hours followed by cooling at room temperature to obtain black colored Ni foam in the solution;
e) removing black colored Ni foam obtained in step (d) from the solution, followed by washing several times with the de-ionized water and drying at room temperature overnight, to obtain Sodium Sulphide induced Nickel-iron (oxy) hydroxide-based 3D electrode (S-NiFeOOH);
III: Electrochemical activation of the catalyst on the electrode:
f) activating the obtained electrode electrochemically.

The said process in step (c), the pre-processing of Ni foam comprises the steps of:
sonication of commercially obtained Ni foam with HCl for 15 minutes to remove surface oxide or any other greasing materials, followed by consecutive washing with De-ionized water and ethanol; and drying the washed Ni foam.

The said process in step (d), the auto clave is kept in an oven at 80⁰C for 18 hours.

The aim of the present invention is to develop a novel kind of electrode material S-NiFeOOH which can be utilized for various electrocatalytic and other catalytic applications.

BRIEF DRSCRIPTION OF DRAWINGS:

The drawings described herein are intended to provide a further understanding of the invention and are intended to be a part of the invention. However, the drawings as shown are representative and non-limiting the scope of the invention. In the drawings:

Fig. 1 shows the schematic diagram for the synthesis of Oxygen evolution reaction (OER) Electrode (S-NiFeOOH) of the present invention.

Fig. 2 shows the graph representation of three-dimensional electrode of the present invention wherein all electrochemical measurements are performed in 2M KOH + 0.5 M NaCl solution.
Fig. 2(a) shows the OER LSV.
Fig. 2(b) shows a Tafel slope.
Fig. 2(c) shows Impendence measurement done at 0.00V in the fixed frequency region.
Fig. 2(d) shows Impendence measurement done at 1.45V in the fixed frequency region.
Fig. 2(e) & (f) shows ECSA measurements of electrode.

Fig. 3(a) shows the XRD measurement of three-dimensional electrode of the present invention.

Fig. 3(b) shows the AFM of electrode surfaces (Scratched) of three-dimensional electrode of the present invention.

Fig. 4 shows the graph representation of XPS survey of three-dimensional electrode surfaces of the present invention.
Fig. 4(a) shows Ni 2p scan.
Fig. 4(b) shows XPS spectra Fe 2p scan.
Fig. 4(c) shows XPS spectra Co 2p scan.
Fig. 4(d) shows XPS spectra S 2p scan.
Fig. 4(e) shows XPS spectra O 1s scan.

DETAILED DESCRIPTION OF THE INVENTION:

The present invention relates to a three-dimensional electrode for seawater electrolysis.

The said three-dimensional electrode of the present invention favors the high catalytic activity for Oxygen evolution reaction (OER) while suppresses the Chlorine evolution reaction (CER) by forming an in-situ anionic layer on it which repel the chloride anions from the surface of electrode.

Most of the known electrocatalysts are unable to sustainably carry out electrolysis of sea water since Chlorine evolution reaction (CER) competes with the Oxygen evolution reaction (OER). The present invention utilizes a novel catalyst system that is selective towards Oxygen evolution reaction (OER) compared to that of the Chlorine evolution reaction (CER) and possibly the in-situ formed anionic layer stops the transport of chloride anion towards the electrode surface, the product became viable for sustainable sea water electrolysis. The invention is about product i.e. catalyst and subsequent electrode for electrocatalysis.

The aim of the present invention is to develop a novel kind of electrode material S-NiFeOOH which can be utilized for various electrocatalytic and other catalytic applications. The three-dimensional electrode of the present invention possesses an excellent activity with higher current density at a very low value of the potential. The electrode is capable of sustainably performing the electrolysis of chloride containing water for a very long period.

The reported catalysts so far have not been successful to electrolyze sea water for long duration. The existing catalysts are also known to generate low current density, high cost.

The present invention discloses a three-dimensional electrode for seawater electrolysis. So far in the literature, the metal oxide nanoparticles are first synthesized, and then subsequently converted into nano metal oxyhydroxides via heat treatment and then treat with Sulphur to synthesize the corresponding metal sulphide nano catalysts. In the present invention, the metal salts are directly synthesized the S-doped metal oxyhydroxides nano catalysts using a very common Sulfide precursor.

Further, the invention discloses the three-dimensional electrode which is suitable for direct electrolysis of chloride containing water. The electrode is able to generate high current density over a long period of time. The electrode can be synthesized in a large scale in an economical manner without using any sophistication reaction set up.

A novel catalyst composition and a novel procedure to fabricate the 3D electrode has been developed.

Three-dimensional Electrode:

The present invention discloses a three-dimensional electrode for seawater electrolysis, characterized in that, the electrode comprises nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam.

The said three-dimensional electrode favors high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

The inventors of the present invention have developed a Nickel-iron (oxy) hydroxide-based 3D electrode for selective Oxygen evolution reaction (OER).

The said electrode is a Sodium sulphide induced iron (oxy) hydroxide based three-dimensional electrode.

In the preferred embodiment, the present invention discloses a novel kind of electrode material (S-NiFeOOH) which is extremally helpful in direct sustainable seawater electrolysis process.

The present invention discloses a Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode. The three-dimensional electrode possesses high catalytic activity for Oxygen evolution reaction (OER) while suppressing the Chlorine evolution reaction (CER), by forming an in-situ anionic layer on it repelling the chloride anions from the surface of electrode.

The said electrode performs Oxygen evolution reaction (OER) efficiently in two-electrode electrolyzer set up to 2.5 V without evolution of any chlorine ions. The in-situ formed anionic layer is able to repel the chloride anions without affecting the performance of Oxygen evolution reaction (OER) activity. Therefore, the electrode is capable to sustain performing the electrolysis of chloride containing water, such as seawater/low grade water/ground water.

The final OER electrode shows an excellent activity with 400 mA/cm2 current density at a potential of 1.6 V vs RHE (overpotential of 370 mV). Overall, the electrode is capable of sustainably performing the electrolysis of chloride containing water for a very long period.

The electrode is active at a temperature range 25ºC to 70ºC and in all basic pH condition.

The major problems which are solved by the present invention, that are chiefly associated with sea water splitting, are
- Lowered the overpotential required for Oxygen evolution reaction (OER) to make it commercially viable,
- Prevented chlorine evolution reaction (CER). Selective OER than CER by electrode is the most important challenge under this operation. The minimization of CER is only possible by having electrode specific to OER and have chlorine repellent properties. The S-NiFeOOH electrode of the present invention has the strong tendency to repel chlorine ions and is specific for OER process. This is possible because the in-situ formed anionic layer stops the transport of chloride anion towards the electrode surface. Thus, the product became viable for sustainable sea water electrolysis.
- Increasing the catalyst life by reducing catalyst degradation & deactivation during sea water electrolysis

The present invention provides electrode that have high catalytic activity for OER while suppresses the CER by forming an in-situ anionic layer on it which repel the chloride anions from the surface of electrode. The final OER electrode shows an excellent activity at a very high current density at a low value of potential. Overall, the electrode is capable of sustainably performing the electrolysis of chloride containing water for a very long period.

The present invention discloses a starting material possessing a nanometallic material. The starting material possessing having similar functionality can be varied to certain extent. For example, using sulphur containing precursors can tune the functionality and activity of the electrode. Similarly, using phosphorous containing functional groups can also be implemented. Use of a sacrificial agent that first acts as a reagent and subsequently leaves by allowing the formation of catalysts on the surface. The process involves one-step synthesis and the control over the catalyst composition is tailored.

With all prior knowledge, the present invention forward towards the process for preparation and have synthesized a specific electrode.

Process for preparation of three-dimensional electrode:

The present invention discloses a process for preparation of three-dimensional electrode for seawater electrolysis of the present invention with the simple steps involving:
• Growth of catalysts on the activated commercial electrodes;
• Synthesis of nano catalyst; and
• Electrochemical catalyst activation.

In the prior art process, the metal oxide nanoparticles are first synthesized, and these are subsequently converted into nano metal oxyhydroxides via heat treatment and then treat with Sulphur to synthesize the corresponding metal sulphide nano catalysts. The present invention discloses use of metal salts to directly synthesize the S-doped metal oxyhydroxides nano catalysts using a very common Sulfide precursor.

The present invention utilizes a two-step procedure. The electrode is first treated with the precursors hydrothermally and then further activated electrochemically.

Fig. 1 shows the schematic diagram for the synthesis of three-dimensional electrode.

Present invention discloses a process for preparation of Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode, wherein the process comprises steps of:
I: Controlled precursor mixing:
a) separately dissolving Ferric nitrate nonahydrate and Sodium Sulfide in De- ionized water forming, solution A and solution B respectively;
b) adding solution B in solution A dropwise via continuous stirring till the appearance of black turbidity in the reaction mixture;
II: Catalyst formation via hydrothermal procedure:
c) immersing pre-processed Ni foam into the reaction mixture of step (b) and transferring it into a Teflon lined autoclave and sealed tightly;
d) keeping the auto clave in an oven at a temperature range between 70⁰C to 100⁰C for 18 hours followed by cooling at room temperature to obtain black colored Ni foam in the solution;
e) removing black colored Ni foam obtained in step (d) from the solution, followed by washing several times with the deionized water and drying at room temperature overnight, to obtain Sodium sulphide induced Nickel-iron (oxy) hydroxide-based 3D electrode (S-NiFeOOH);
III: Electrochemical activation of the catalyst on the electrode.
f) activating the obtained electrode electrochemically.

The pre-processing of Ni foam used in the present invention comprises the steps of:
sonication of commercially obtained Ni foam with HCl for 15 minutes to remove surface oxide or any other greasing materials, followed by consecutive washing with De-ionized water and ethanol; and drying the washed Ni foam.

Above described each step is further defined below:

Controlled precursor mixing

This is the initial step of preparing the three-dimensional electrode. Two solutions
namely solution A and solution B are prepared for making a reaction mixture. The said step comprises:

- Preparing solution A by dissolving Ferric nitrate nonahydrate in De-ionized water;

- Preparing solution B by dissolving Sodium Sulfide in De-ionized water;

- Adding solution B in solution A by dropwise addition;

- The drop-wise addition is continued till the appearance of black turbidity in the reaction mixture;

- When the reaction mixture becomes turbid, the further addition is stopped.

Catalyst formation via hydrothermal procedure

In this step catalyst is prepared via simple hydrothermal approach. In this step the pre-processed Ni foam which is sonicated with the HCl, is immersed into the reaction mixture of above step to form the three-dimensional electrode. The said step comprises:

- Immersing the pre-processed Ni foam into the reaction mixture which is prepared in above step;

- Transferring the immersed Ni foam into a Teflon lined auto clave and sealed tightly.

- The auto clave is kept in an oven at temperature ranging from 70 ºC to 100 ºC for 18 hours. Preferably, the auto clave is kept in an oven at 80 ⁰C for 18 hours.

- After completion of 18 hours the auto clave is left for cooling at room temperature.

- The obtained black coloured Ni foam is taken out from the solution and washed several times with the De-ionized water and dried at room temperature overnight.

Though hydrothermal process has been utilized in literature to synthesize the catalysts, the role of the processes in this invention is different. This invention utilizes a procedure to synthesize a 3D electrode catalyst for OER. In this invention, the precursors used, and the catalyst obtained is new.

Electrochemical catalyst activation

The above obtained 3D electrode catalyst is further activated electrochemically.

The reaction conditions are achievable with the use of readily available equipment such as autoclaves, stirrer, potentiostat etc. The precursor mixing conditions need to be maintained as per the given protocol to produce materials with desired efficiency. The synthesis condition may be altered by minor degree depending upon the starting material used, though this is easily achievable by a person well versed with the Art.

The products of the process are typically nanometallic S-doped metal oxyhydroxides flakes grown on Ni foam. Specifically, the said process results in formation of Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode. These can be utilized for various electrocatalytic and other catalytic applications. Further modification of catalyst structure may lead to electro-photocatalytic applications. Typically, the catalysts are suitable for electrolysis of H2O and may be utilized for CO2 conversion.

EXAMPLES:

Example I- Process for preparation of three-dimensional electrode

The Sodium sulphide induced Nickel-iron (oxy) hydroxide (S-NiFeOOH) three-dimensional electrode was prepared by the following procedure:

The commercially obtained Ni foam was sonicated with 3M HCl for 15 minutes to remove surface oxide or any other greasing materials, followed by consecutive washing with De-ionized water and ethanol, thrice. The washed Ni foam was dried in the air.

A weighed amount of 375mg of Ferric nitrate nonahydrate (Fe (NO3)3.9H2O) was dissolved in 15ml of De-ionized water, which was named as solution A. Another solution named B was prepared by dissolving 15 mg of Sodium Sulfide (Na2S.xH2O) in 10ml of De-ionized water.

A very little amount of solution B was added in solution A by dropwise addition. The drop-wise addition was continued till the appearance of black turbidity in the reaction mixture. When the reaction mixture becomes turbid, the further addition was stopped, and the piece of above described Ni foam of size (2.5*1 cm2) was immersed into the solution.

Then it was transferred into a 25 mL Teflon lined auto clave and sealed tightly. The auto clave was kept in an oven at 80oC for 18 hours. After completion of 18 hours the auto clave was left for cooling at room temperature and the obtained black colored Ni foam was taken out from the solution. The obtained black colored Ni foam was washed several times with the De-ionized water and dried at room temperature overnight.

Fig. 1 shows the schematic diagram for the synthesis of three-dimensional electrode as described in this example.

Example-II- Three-dimensional Electrode Analysis

The above obtained three-dimensional electrode is analysed, and the results are shown in figure 2 to figure 4.

Figure 2 shows the graph representation of the obtained three-dimensional electrode where all the electrochemical measurements were performed in 2M KOH + 0.5 M NaCl solution.

Figure 2(a) shows the Linear sweep voltammetry (LSV) curves. Where at a very low potential (1.6 V) high current density i.e. 400 mA/cm2 was obtained.

Figure 2(b) shows a Tafel slope which shows how efficiently electrode can produce current in response to change in applied potential.

Figure 2(c) shows Impendence measurement done at 0.00V in the fixed frequency region.

Figure 2(d) shows Impendence measurement done at 1.45V in the fixed frequency region.

Figures 2(e) and 2(f) show electrochemically active surface area (ECSA) measurements of electrode.

Figures 3(a) and 3(b) show X-ray diffraction (XRD) measurement and AFM of electrode surfaces (Scratched) of the electrode, respectively.

Figure 4 shows the X-ray photoelectron spectroscopy (XPS) analysis of the three-dimensional electrode which shows graph representation of XPS survey of three-dimensional electrode surfaces. Figure 4(a) shows Ni 2p scan. Figure 4(b) shows XPS spectra Fe 2p scan. Figure 4(c) shows XPS spectra Co 2p scan. Figure 4(d) shows XPS spectra S 2p scan. Figure 4(e) shows XPS spectra O 1s scan.

Thus, from the above analysis it is proved that the obtained three-dimensional electrode comprises high catalytic activity for OER and shows excellent activity with 400mA/cm2 current density at a potential of 1.6 V. the electrode can be utilized for various electrocatalytic and other catalytic applications. Further modification of catalyst structure may lead to electro-photocatalytic applications. Typically, the catalysts are suitable for electrolysis of H2O and may be utilized for CO2 conversion.

ADVANTAGES OF THE INVENTION

The major advantages associated with the present innovative three-dimensional electrode are the following:

- Cost effective- The material and equipment such as autoclaves, stirrer, potentiostat etc. used in this process results in low-cost procedure

- Sustainable- The electrode is capable to sustain in performing of electrolysis of chloride containing water for a very long period.

- Easy synthesis- The synthesis process is simple, and the equipment used are cost effective. Thus, it is easily achievable by a person well versed with the Art.

- Commercialization- The said electrode has rendered the possible commercialization of sea water electrolysis for H2 production.

APPLICATIONS

The three-dimensional electrode of the present invention has following applications:

- The electrode is utilized for electrolysis of low grade/ground/sea water.
- The catalyst system may be utilized for catalyzing other chemical reactions.
- The nanomaterials with suitable modification may be utilized for fuel cell applications.

The three-dimensional electrode of the present invention could be used in companies especially working towards commercialization of electrolyzers and production of H2, i.e. for example various oil & gas domain public sector and private sector companies.

Presumably, this has substantial commercial application in electrolyzers.