METHOD FOR SYNTHESIZING BIMETALLIC SULFIDE ELECTROCATALYSTS

Abstract

The present disclosure provides a method for synthesizing pentlandite-type bimetallic (Fe.Math.Co)9S8 compounds. The method includes grinding and mixing sulfur powder with metal salts of Fe and Co to form a homogeneous mixture, and conducting solid-state pyrolysis of the mixture at a temperature of 900 C. in an Argon atmosphere. The synthesized (Fe.Math.Co).sub.9S.sub.8 compound can be used as electrode material in electrochemical processes. In some embodiments, the method further includes dispersing the synthesized (Fe.Math.Co).sub.9S.sub.8 in a Nafion and isopropanol mixture to form a suspension, and coating the suspension on a glassy carbon electrode to form an electrode comprising (Fe.Math.Co).sub.9S.sub.8 pentlandite. The method provides a streamlined approach to synthesizing (Fe.Math.Co).sub.9S.sub.8 pentlandite, a material with potential applications in renewable energy technologies including electrocatalyst for OER in water splitting for hydrogen production.

Claims

1. A method for synthesizing bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite, the method comprising: grinding and mixing sulfur powder with metal salts of Fe and Co to form a homogeneous mixture; and performing solid state pyrolysis of the homogeneous mixture at a temperature of 900 C. in an Argon atmosphere to obtain (Fe.Math.Co).sub.9S.sub.8 pentlandite.

2. The method of claim 1, wherein the sulfur powder, and the metal salts of Fe and Co have a purity greater than 99.9%.

3. The method of claim 1, wherein the metal salts of Fe and Co are present in an equimolar ratio in the homogeneous mixture.

4. The method of claim 1, wherein the metal salts of Fe and Co include iron nitrate and cobalt nitrate respectively.

5. The method of claim 4, wherein sulfur is ground and mixed together with iron nitrate and cobalt nitrate in a stoichiometric molar ratio of 1.78:1:1 to obtain the homogeneous mixture.

6. The method of claim 1, wherein the metal salts of Fe and Co are a chloride salt or an acetate salt.

7. The method of claim 1, wherein the solid-state pyrolysis is performed in a furnace with controlled temperature ramping rate of 5 C. min.sup.1 until a temperature of 900 C. is achieved.

8. The method of claim 1, wherein the solid-state pyrolysis is performed for 10 hours.

9. A method for synthesizing bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite, comprising: grinding and mixing sulfur powder with Fe(NO.sub.3).sub.3.Math.9H.sub.2O and Co(NO.sub.3).sub.2.Math.6H.sub.2O until a homogeneous mixture is formed; and conducting a thermal treatment of the homogeneous mixture in a furnace at a temperature of 900 C. under Argon flow for 10 h to obtain (Fe.Math.Co).sub.9S.sub.8 pentlandite.

10. The method of claim 9, wherein sulfur is ground and mixed together with Fe(NO.sub.3).sub.3.Math.9H.sub.2O and Co(NO.sub.3).sub.2.Math.6H.sub.2O in a stoichiometric molar ratio of 1.78:1:1 to obtain the homogeneous mixture.

11. The method of claim 9, wherein the grinding and mixing of sulfur powder with Fe (NO.sub.3).sub.3.Math.9H.sub.2O and Co(NO.sub.3).sub.2.Math.6H.sub.2O is performed in a ball mill.

12. The method of claim 9, wherein the grinding and mixing of sulfur powder with Fe(NO.sub.3).sub.3.Math.9H.sub.2O, Co(NO.sub.3).sub.2.Math.6H.sub.2O is performed using a mechanical mixer at a speed of 500 rpm.

13. The method of claim 9, wherein the thermal treatment is performed in a furnace with controlled temperature ramping rate of 5 C. min.sup.1 until a temperature of 900 C. is achieved.

14. The method of claim 9, wherein prior to thermal treatment the homogenous mixture is loaded in a porcelain alumina boat to be placed in the furnace to avoid chemical contamination.

15. A method for synthesizing an electrode comprising bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite, the method comprising: grinding and mixing sulfur powder with metal salts of Fe and Co to form a homogeneous mixture; performing solid state pyrolysis of the homogeneous mixture in a furnace at a temperature of 900 C. for 10 hours to obtain (Fe.Math.Co).sub.9S.sub.8 pentlandite; dispersing the (Fe.Math.Co).sub.9S.sub.8 pentlandite in a Nafion and isopropanol mixture to form a suspension; and coating the suspension on a glassy carbon electrode to form an electrode comprising the (Fe.Math.Co).sub.9S.sub.8 pentlandite.

16. The method of claim 15, wherein the metal salts of Fe and Co include iron nitrate and cobalt nitrate mixed in an equimolar ratio.

17. The method of claim 15, wherein the grinding and mixing of sulfur powder with metal salts of Fe and Co is performed in a ball mill.

18. The method of claim 15, wherein the Nafion and isopropanol mixture comprises 5% Nafion and the remainder being isopropanol.

19. The method of claim 15, wherein dispersing the (Fe.Math.Co).sub.9S.sub.8 pentlandite in a Nafion and isopropanol mixture is performed using a sonicator operates at a power of 100 W and a frequency of about 42 kHz.

20. The method of claim 15, wherein coating the suspension on a glassy carbon electrode is performed by at least one of drop casting, dip coating or spray coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A further understanding of the nature and advantages of particular embodiments may be realized by reference to the remaining portions of the specification and the drawings, in which like reference numerals are used to refer to similar components. When reference is made to a reference numeral without specification to an existing sub-label, it is intended to refer to all such multiple similar components.

[0024] FIG. 1 is a process flow diagram of a method of synthesis of pentlandite-type (Fe.Math.Co).sub.9S.sub.8 material, according to an embodiment;

[0025] FIG. 2 is a process flow diagram of a method of synthesis of pentlandite-type (Fe.Math.Co).sub.9S.sub.8 electrode, according to an embodiment;

[0026] FIG. 3 is an electrode comprising a coating of a pentlandite-type (Fe.Math.Co).sub.9S.sub.8 material, according to an embodiment; and

[0027] FIG. 4 is an electrochemical cell comprising a pentlandite-type (Fe.Math.Co).sub.9S.sub.8 coated electrode for water electrolysis, according to an embodiment.

[0028] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION

[0029] While various aspects and features of certain embodiments have been summarized above, the following detailed description illustrates a few exemplary embodiments in further detail to enable one skilled in the art to practice such embodiments. The described examples are provided for illustrative purposes and are not intended to limit the scope of the invention.

[0030] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the described embodiments. It will be apparent to one skilled in the art however that other embodiments of the present invention may be practiced without some of these specific details. Several embodiments are described herein, and while various features are ascribed to different embodiments, it should be appreciated that the features described with respect to one embodiment may be incorporated with other embodiments as well. By the same token however, no single feature or features of any described embodiment should be considered essential to every embodiment of the invention, as other embodiments of the invention may omit such features.

[0031] In this application the use of the singular includes the plural unless specifically stated otherwise and use of the terms and and or is equivalent to and/or, also referred to as non-exclusive or unless otherwise indicated. Moreover, the use of the term including, as well as other forms, such as includes and included, should be considered non-exclusive. Also, terms such as element or component encompass both elements and components including one unit and elements and components that include more than one unit, unless specifically stated otherwise.

[0032] Lastly, the terms or and and/or as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, A, B or C or A, B and/or C mean any of the following: A; B; C; A and B; A and C; B and C; A, B and C. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

[0033] As this invention is susceptible to embodiments of many different forms, it is intended that the present disclosure be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described.

[0034] The terms pentlandite and pentlandite-type are used interchangeably to mean a pentlandite-type phase of (Fe.Math.Co).sub.9S.sub.8 synthesized according to various embodiments of the instant invention.

[0035] The following description sets forth exemplary aspects of the present disclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0036] The present disclosure pertains to a method for synthesizing bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite, a compound with potential applications in various fields, including electrocatalysis. Specifically, the method may involve a one-step solid pyrolysis synthesis, which may offer a simplified and efficient approach to producing this compound. The method may also include subsequent steps such as dispersing the synthesized compound in a specific mixture and measuring its electrochemical activity towards the oxygen evolution reaction, a process of interest in the field of water splitting to produce hydrogen. In some aspects the catalyst may be used for hydrogen evolution reaction in water splitting. In some aspects, the catalyst may be used of oxygen reduction reaction in fuel cells.

[0037] In some aspects, the method of forming (Fe.Math.Co).sub.9S.sub.8 pentlandite may involve grinding and mixing high-purity metal salts and sulfur powder until a homogeneous mixture is formed. This mixture may then be transferred to a porcelain alumina boat for solid state pyrolysis at a specific temperature. The resulting product, (Fe.Math.Co).sub.9S.sub.8 pentlandite, may then be dispersed in a Nafion and isopropanol mixture. The electrochemical activity of the compound towards the oxygen evolution reaction may then be measured, providing valuable information about its potential as an electrocatalyst.

[0038] The disclosed method may offer several potential benefits. For instance, the one-step solid pyrolysis synthesis may simplify the production process of (Fe.Math.Co).sub.9S.sub.8 pentlandite, potentially reducing the time, cost, and complexity associated with its formation. Additionally, the method may allow for precise control over the composition and properties of the synthesized compound, which may be beneficial in optimizing its performance as an electrocatalyst.

[0039] FIG. 1 shows a process flow diagram of a method of synthesis of pentlandite-type (Fe.Math.Co).sub.9S.sub.8 material. The method involves a step 202 where 202 grinding and mixing Sulfur powder with metal salts of Fe and Co is performed to form a homogeneous mixture. This is followed by step 204 where Thermal Treatment of the homogeneous mixture in a furnace at a temperature around 900 C. under Argon atmosphere to form pentlandite type (Fe.Math.Co).sub.9S.sub.8 catalyst material.

[0040] In some aspects, process may involve the use of specific metal salts, such as iron nitrate Fe(NO.sub.3).sub.3.Math.9H.sub.2O and cobalt nitrate (Co(NO.sub.3).sub.2.Math.6H.sub.2O) and sulfur powder. The grinding and mixing process may continue until a homogeneous mixture is formed. The formation of a homogeneous mixture may ensure that the metal salts and sulfur are evenly distributed throughout the mixture, which may contribute to the uniformity and consistency of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0041] In some aspects, the grinding and mixing of sulfur powder with metal salts of Fe and Co may be performed in a ball mill. The ball mill may provide a high-energy mechanical force that facilitates the thorough mixing of the sulfur powder with the metal salts. This may result in a homogeneous mixture, which is a prerequisite for the successful synthesis of the pentlandite-type (Fe.Math.Co).sub.9S.sub.8 compound. The use of a ball mill may also allow for the control of the particle size of the mixture, which may influence the properties of the resulting compound.

[0042] The ball mill may operate at a specific speed and for a specific duration to ensure a thorough mixing of the sulfur powder with the metal salts. For example, the ball mill may operate at a speed in the range between about 500 rpm and about 5000 rpm for a duration between about 15 mins and about 3 hours. This specific speed and duration may be chosen to optimize the grinding and mixing process, leading to a homogeneous mixture of sulfur powder and metal salts. However, the exact speed and duration of the ball mill operation may be adjusted based on factors such as the specific properties of the sulfur powder and the metal salts, the desired particle size of the mixture, and the specific characteristics of the ball mill.

[0043] In some aspects, the ball mill may be equipped with specific features to facilitate the grinding and mixing process. For instance, the ball mill may include a grinding chamber, a number of grinding balls, and a motor to drive the grinding balls. The grinding chamber may be designed to accommodate the sulfur powder and the metal salts, and the grinding balls may be designed to grind and mix the sulfur powder and the metal salts when driven by the motor. The specific design and operation of the ball mill may contribute to the formation of a homogeneous mixture of sulfur powder and metal salts, which is a prerequisite for the successful synthesis of the pentlandite-type (Fe.Math.Co).sub.9S.sub.8 compound.

[0044] In some aspects, the process of grinding and mixing of the sulfur powder with the metal salts of Fe and Co can be performed in a mechanical mixer. In some aspects, the mechanical mixing is performed at a speed around 500 rpm. In some aspects, the mechanical mixing is performed at a speed between about 300 rpm and about 2000 rpm. In some aspects, the mechanical mixing is performed at a speed between about 300 rpm and about 600 rpm. In some aspects, the mechanical mixing is performed at a speed between about 600 rpm and about 1000 rpm. In some aspects, the mechanical mixing is performed at a speed between about 1000 rpm and about 2000 rpm.

[0045] In some embodiments, the mechanical mixing is performed for 2 hours. In some embodiments, the mechanical mixing is performed for a time between about 10 mins and 2 hours. In some embodiments, the mechanical mixing is performed for a time between about 10 mins and about 30 mins. In some embodiments, the mechanical mixing is performed for a time between about 30 mins and about 1 hour. In some embodiments, the mechanical mixing is performed for a time between about 1 hour and about 2 hours.

[0046] The sulfur powder and the metal salts of Fe and Co used in the method are chosen to have high purity. In some aspects, the purity of sulfur powder and the metal salts of Fe and Co used in the method greater than 99.9%. In some aspects, the purity of sulfur powder and the metal salts of Fe and Co used in the method is in the range between about 99.9% and about 99.9999%. In some aspects, the purity of sulfur powder and the metal salts of Fe and Co used in the method is in the range between about 99.99% and about 99.9999%. In some aspects, the purity of sulfur powder and the metal salts of Fe and Co used in the method is in the range between about 99.999% and about 99.9999%.

[0047] In some cases, the metal salts of Fe and Co may be mixed in an equimolar ratio. This balanced proportion of the two metals in the mixture may facilitate the formation of the pentlandite-type (Fe.Math.Co).sub.9S.sub.8 compound, as it may provide an equal number of Fe and Co atoms for the chemical reactions during the solid-state pyrolysis. In some aspects, sulfur is ground and mixed together with iron salt and cobalt salt in a stoichiometric molar ratio of 1.78:1:1 to obtain the homogeneous mixture

[0048] In some aspects, sulfur is ground and mixed together with iron nitrate and cobalt nitrate in a stoichiometric molar ratio of 1.78:1:1 to obtain the homogeneous mixture. In an exemplary embodiment, the quantities may be 1.67 g (29.8 mmol) of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 1.75 g (29.8 mmol) of Co(NO.sub.3).sub.2.Math.6H.sub.2O, and 1.70 g (53.1 mmol) of sulfur. The use of these specific quantities may be based on stoichiometric considerations and may contribute to the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite with a desired composition and properties. However, it is to be understood that other quantities of these components may also be used, depending on the specific requirements of the synthesis process and the desired properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0049] In some embodiments, the metal salts of Fe and Co may include iron nitrate Fe(NO.sub.3).sub.3.Math.9H.sub.2O and cobalt nitrate (Co(NO.sub.3).sub.2.Math.6H.sub.2O) respectively. These specific salts may be chosen due to their reactivity and availability. However, other salts of Fe and Co, such as chloride or acetate salts, may also be used in other embodiments. In one exemplary embodiment, ferric acetate and cobalt acetate are used instead of ferric nitrate and cobalt nitrate.

[0050] Once the homogeneous mixture is formed, it may undergo solid-state pyrolysis. This process may involve heating the mixture in a furnace at a temperature of 900 C. in an inert atmosphere, such as an argon atmosphere, to induce the desired chemical reactions between the sulfur and the metal salts. This may result in the formation of the pentlandite-type (Fe.Math.Co).sub.9S.sub.8 compound.

[0051] In some aspects, the homogeneous mixture in transferred to the furnace in a porcelain alumina boat. This boat may serve as a suitable container for the subsequent solid state pyrolysis process. This process may be an integral part of the method of forming (Fe.Math.Co).sub.9S.sub.8 pentlandite The transfer process may be carried out with care to ensure that the homogeneous mixture is evenly distributed within the porcelain alumina boat. This even distribution may contribute to the uniform heating of the mixture during the pyrolysis process, which may in turn enhance the consistency and quality of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0052] The use of iron nitrate, cobalt nitrate, and sulfur powder as a source of sulfur may also contribute to the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite with a desired composition and properties. In some aspects, the use of a porcelain alumina boat is preferred to ensure that there is no contamination of another chemical species which may disrupt the chemical reaction or the formation of the specific pentlandite phase, or lead to chemical impurities that may affect the electrocatalytic performance of the (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0053] In some aspects, the transfer process may be performed manually or with the aid of suitable tools or equipment. The specific method of transfer may depend on various factors, such as the size and shape of the porcelain alumina boat, the quantity of the homogeneous mixture, and the specific requirements of the synthesis process. Regardless of the specific method of transfer, the goal may be to ensure that the homogeneous mixture is properly positioned within the porcelain alumina boat for the subsequent solid state pyrolysis process without any contamination.

[0054] In some cases, the porcelain alumina boat containing the homogeneous mixture may then be placed in a suitable furnace or oven for the solid-state pyrolysis process. The furnace or oven may be preheated to a specific temperature, such as 900 C., to facilitate the pyrolysis process. The porcelain alumina boat may be positioned within the furnace or oven in a manner that allows for uniform heating of the homogeneous mixture. This uniform heating may contribute to the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite with a desired composition and properties.

[0055] In some aspects, the transfer of the homogeneous mixture to the porcelain alumina boat and the subsequent solid state pyrolysis process may be performed under controlled conditions to ensure the quality and consistency of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite. These controlled conditions may include, for example, a specific temperature, pressure, and atmosphere. The specific conditions may be selected based on the specific requirements of the synthesis process and the desired properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0056] In some aspects, the solid-state pyrolysis process may involve the pyrolysis of iron nitrate, cobalt nitrate, and sulfur powder at a specific temperature, such as 900 C. This temperature may be selected to facilitate the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite from the mixture of these components. The pyrolysis process may involve heating the mixture at this temperature for a specific duration, which may be, for example, 10 hours. This duration may be selected based on the specific requirements of the synthesis process and the desired properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0057] In some aspects, the solid-state pyrolysis is performed for a time greater than 10 hours. In some aspects, the solid-state pyrolysis is performed for a time between about 10 hours and about 24 hours. In some aspects, the solid-state pyrolysis is performed for a time between about 10 hours and about 15 hours. In some aspects, the solid-state pyrolysis is performed for a time between about 15 hours and about 20 hours. In some aspects, the solid-state pyrolysis is performed for a time between about 10 hours and about 24 hours. In some aspects, the solid-state pyrolysis is done for a time sufficient to ensure the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite phase. In some aspects, the time of thermal treatment is optimized iteratively by performing the pyrolysis for a specific amount of time and then performing materials characterization to check whether (Fe.Math.Co).sub.9S.sub.8 pentlandite phase is formed.

[0058] In some aspects, the solid-state pyrolysis process may be performed in a suitable furnace or oven, which may be capable of maintaining a specific temperature and ramping rate. The furnace or oven may also be capable of providing a controlled atmosphere, which may be beneficial in preventing unwanted reactions or the formation of by-products during the pyrolysis process. The specific type and design of the furnace or oven may depend on various factors, such as the specific requirements of the synthesis process, the quantity of the homogeneous mixture, and the desired properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0059] In an exemplary embodiment, the thermal treatment of the mixture during the pyrolysis process may involve a ramping of 5 C. min.sup.1. This ramping rate may be selected to ensure a gradual and controlled increase in temperature, which may contribute to the formation of (Fe.Math.Co).sub.9S.sub.8 pentlandite with a desired composition and properties. The use of a specific ramping rate may also help to prevent rapid or uneven heating of the mixture, which could potentially lead to the formation of unwanted by-products or inconsistencies in the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0060] The resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite may then be collected from the porcelain alumina boat and subjected to further processing or analysis. For instance, the (Fe.Math.Co).sub.9S.sub.8 pentlandite may be dispersed in a Nafion and isopropanol mixture, coated on a glassy carbon electrode to prepare an electrocatalytic electrode, and its electrochemical activity towards the oxygen evolution reaction may be measured. These subsequent steps may provide valuable information about the performance of the synthesized (Fe.Math.Co).sub.9S.sub.8 pentlandite as an electrocatalyst.

[0061] Material characterization of synthesized (Fe.Math.Co).sub.9S.sub.8 Pentlandite may be performed to analyze its various attributes which may be useful in further optimization of the synthesis process. In one exemplary embodiment, the synthesized (Fe.Math.Co).sub.9S.sub.8 pentlandite synthesized using process 102 underwent a comprehensive material characterization to assess its structural and elemental attributes. XRD analysis involved obtaining the XRD pattern to validate the crystalline structure, comparing observed peaks with the simulated pattern of pentlandite (JCPDS #01-086-2273). SEM and TEM analysis were employed to investigate the material's morphology, revealing nanostructured (Fe.Math.Co).sub.9S.sub.8 pentlandite with distinctive porous features. XPS analysis confirmed the oxidation states of Fe, Co, and S, providing evidence of the successful synthesis of pentlandite. Additionally, EDX elemental mapping demonstrated the uniform dispersion of Fe, Co, and S throughout the material, emphasizing its compositional homogeneity. This collective characterization illuminates the synthesized (Fe.Math.Co).sub.9S.sub.8 pentlandite's key structural and elemental properties.

[0062] In some embodiments, the (Fe.Math.Co).sub.9S.sub.8 pentlandite is nanostructured with particle size in the range between about 10 nm and 500 nm. In some aspects, the nanoscale particle size of the pentlandite (Fe.Math.Co).sub.9S.sub.8 enhances the electrocatalytic performance. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 5 nm and 200 nm. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 5 nm and 20 nm. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 20 nm and 50 nm. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 50 nm and 100 nm. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 100 nm and 200 nm. In some embodiments, the particle size of pentlandite (Fe.Math.Co).sub.9S.sub.8 is in the range between about 200 nm and 500 nm.

[0063] In some embodiments, the pentlandite (Fe.Math.Co).sub.9S.sub.8 synthesized using the process described in this disclosure is porous. In some embodiments, the pentlandite (Fe.Math.Co).sub.9S.sub.8 has porosity between about 5% and 70%. In some embodiments, the pore sizes in the coating are between about 10 nm and about 100 nm. In some embodiments, the porosity enhances the electrocatalytic performance of the pentlandite by providing high surface area for the electron transfer processes.

[0064] FIG. 2 shows a process flow diagram of a method of synthesis of pentlandite-type (Fe.Math.Co).sub.9S.sub.8 electrode. The steps 202 and 204 are identical to steps 102 and 104 respectively, as described in previous sections of this disclosure. Once the (Fe.Math.Co).sub.9S.sub.8 pentlandite is synthesized by thermal treatment, it is dispersed in step 206 in a mixture of Nafion and Isopropanol to form a suspension. Subsequently, in step 208, an electrocatalytic electrode comprising (Fe.Math.Co).sub.9S.sub.8 catalyst material is obtained by coating a glassy carbon electrode with the suspension.

[0065] In some aspects, the step 206 of dispersion of the (Fe.Math.Co).sub.9S.sub.8 pentlandite in the Nafion and isopropanol mixture may involve the use of a sonicator. The sonicator may operate at a power output of about 100 W and a frequency of about 42 kHz. These specific operating conditions may be selected to ensure effective dispersion of the (Fe.Math.Co).sub.9S.sub.8 pentlandite in the mixture. The sonicator may generate high-frequency sound waves that agitate the mixture, facilitating the dispersion of the (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0066] In some cases, the dispersion process may involve the use of a specific volume of the Nafion and isopropanol mixture. For instance, the volume may be 100 L, which may include 5% Nafion and the remainder being isopropanol. This specific volume and composition of the mixture may be selected to ensure effective dispersion of the (Fe.Math.Co).sub.9S.sub.8 pentlandite and to facilitate subsequent electrochemical measurements. However, it is to be understood that other volumes and compositions of the Nafion and isopropanol mixture may also be used, depending on the specific requirements of the dispersion process and the desired properties of the resulting dispersion.

[0067] In some aspects, the dispersion of the (Fe.Math.Co).sub.9S.sub.8 pentlandite in the Nafion and isopropanol mixture may be performed under controlled conditions to ensure the quality and consistency of the resulting dispersion. These controlled conditions may include, for example, a specific temperature, pressure, and sonication duration. The specific conditions may be selected based on the specific requirements of the dispersion process and the desired properties of the resulting dispersion.

[0068] The coating of the suspension on the glassy carbon electrode may be performed by various methods, such as drop casting, dip coating, or spray coating. The choice of coating method may depend on factors such as the specific properties of the suspension, the desired thickness of the coating, and the specific characteristics of the glassy carbon electrode.

[0069] FIG. 3 shows an electrode 300 comprising a coating of a pentlandite-type (Fe.Math.Co).sub.9S.sub.8 material fabricated by the process described in FIG. 2. As shown, the electrode comprises a glassy carbon electrode 302 acting as a substrate on which a coating 304 of pentlandite (Fe.Math.Co).sub.9S.sub.8 pentlandite is deposited using the methods described before. The glassy carbon electrode is connected to a metallic connector or metallic wire 306. The coating 304 has continuous coverage or partial coverage on the glassy carbon electrode 302.

[0070] In some aspects, the (Fe.Math.Co).sub.9S.sub.8 pentlandite coated onto the glassy carbon electrode, which may serve as the working electrode in an electrochemical cell or an electrolytic electrode for OER in a water splitting electrochemical cell. The coating of the (Fe.Math.Co).sub.9S.sub.8 pentlandite onto the glassy carbon electrode may involve the use of a suitable binder, such as Nafion, to ensure a uniform and stable coating. The glassy carbon electrode may be selected for its high conductivity and chemical stability, which may contribute to the accuracy and reliability of the electrochemical measurements.

[0071] In some embodiments, the coating 304 has thickness in the range between about 10 nm and about 2000 nm. In some embodiments, the coating 304 has thickness in the range between about 10 nm and 50 nm. In some embodiments, the coating 304 has thickness in the range between about 50 nm and 100 nm. In some embodiments, the coating 304 has thickness in the range between about 100 nm and 200 nm. In some embodiments, the coating 304 has thickness in the range between about 200 nm and 500 nm. In some embodiments, the coating 304 has thickness in the range between about 500 nm and 1000 nm. In some embodiments, the coating 304 has thickness in the range between about 1000 nm and 2000 nm.

[0072] In some embodiments the coating 304 is nanostructured meaning the grains of the pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating have a nanoscale grain size. In some aspects, the nanoscale grain size of the pentlandite (Fe.Math.Co).sub.9S.sub.8 enhances the electrocatalytic performance of the electrode. In some embodiments, the grain size of pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating is between about 5 nm and 200 nm. In some embodiments, the grain size of pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating is between about 5 nm and 20 nm. In some embodiments, the grain size of pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating is between about 20 nm and 50 nm. In some embodiments, the grain size of pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating is between about 50 nm and 100 nm. In some embodiments, the grain size of pentlandite (Fe.Math.Co).sub.9S.sub.8 in the coating is between about 100 nm and 200 nm.

[0073] In some embodiments, the coating is porous. In some embodiments, the coating has porosity between about 5% and 60%. In some embodiments, the pore sizes in the coating are between about 10 nm and about 100 nm. In some embodiments, the porosity enhances the electrocatalytic performance of the pentlandite. In some embodiments the electrocatalytic performance is due to synergistic catalysis at the interface of glassy carbon with pentlandite.

[0074] FIG. 4 shows an electrochemical system 400 comprising a pentlandite-type (Fe.Math.Co).sub.9S.sub.8 coated electrode for water electrolysis. The electrochemical cell or an electrolyzer for water splitting 402 comprises a cathode 404, an anode 406, a separator 408, and the electrochemical cell is filled with electrolyte 410. The cathode 404 is an electrocatalytic electrode (acting as the OER electrode in water splitting) comprising (Fe.Math.Co).sub.9S.sub.8 pentlandite coated on a glassy carbon electrode which has been described in detail in previous sections. The anode 406 is also an electrocatalytic electrode (where hydrogen is released in water splitting) comprising a catalytic material to catalyze the reaction at the anode. The separator 408 can be a membrane separator as used in the art. The electrolyte 410 comprises water and an alkali (KOH, NaOH), the latter facilitating the rate of the reaction. The power source 412 is the DC power source used to apply the require voltage V (as shown) for the electrochemical reaction. In some aspects the anode 406 also has a coating of (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0075] In some aspects, the electrochemical cell 400 may be used for measuring the electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite towards the oxygen evolution reaction. This measurement may provide valuable information about the performance of the (Fe.Math.Co).sub.9S.sub.8 pentlandite as an electrocatalyst. The measurement of electrochemical activity may involve the use of a three-electrode cell, which may include a graphite rod as a counter electrode, a Hg/HgO as a reference electrode, and a (Fe.Math.Co).sub.9S.sub.8 coated glassy carbon as a working electrode.

[0076] In some aspects, the three-electrode cell may be used in conjunction with an electrochemical workstation for the measurement of the performance of (Fe.Math.Co).sub.9S.sub.8 pentlandite as an electrocatalyst. The electrochemical workstation may be capable of measuring the electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite in a controlled environment, such as in 1 M KOH. This controlled environment may be selected to mimic the conditions under which the (Fe.Math.Co).sub.9S.sub.8 pentlandite may be used as an electrocatalyst, thereby providing a realistic assessment of its performance.

[0077] In some aspects, the graphite rod may serve as a counter electrode in the three-electrode cell. The graphite rod may be selected for its high conductivity and chemical stability, which may contribute to the accuracy and reliability of the electrochemical measurements. The Hg/HgO may serve as a reference electrode, providing a stable and reproducible reference potential against which the potential of the working electrode may be measured.

[0078] In some aspects, the measurement of the electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite may involve the use of specific techniques or methods, such as cyclic voltammetry or chronoamperometry. These techniques or methods may be selected based on their ability to provide accurate and reliable measurements of the electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite. The specific techniques or methods used may depend on various factors, such as the specific requirements of the electrochemical measurements and the desired properties of the (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0079] The following section describe various alternative embodiments of this invention:

[0080] Variations in Metal Salts: The method of synthesizing bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite could be modified by using different types of metal salts. For instance, instead of using iron nitrate (Fe(NO.sub.3).sub.3.Math.9H.sub.2O) and cobalt nitrate (Ni (NO.sub.3).sub.3.Math.6H.sub.2O), other metal salts such as iron chloride (FeCl.sub.3), cobalt chloride (CoCl.sub.2), iron sulfate (FeSO.sub.4), or cobalt sulfate (CoSO.sub.4) could be used. These alternative metal salts could potentially influence the properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite, such as its crystalline structure, morphology, and electrochemical activity.

[0081] Variations in Pyrolysis Temperature: The solid-state pyrolysis process could be conducted at different temperatures. Instead of using a temperature of 900 C., other temperatures could be used, such as 800 C., 850 C., 950 C., or 1000 C. The specific temperature used could influence the properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite, such as its crystalline structure, morphology, and electrochemical activity.

[0082] Variations in Pyrolysis Duration: The duration of the solid-state pyrolysis process could be varied. Instead of conducting the pyrolysis for 10 hours, other durations could be used, such as 8 hours, 9 hours, 11 hours, or 12 hours. The specific duration used could influence the properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite, such as its crystalline structure, morphology, and electrochemical activity.

[0083] Variations in Dispersing Medium: The (Fe.Math.Co).sub.9S.sub.8 pentlandite could be dispersed in different types of mediums. Instead of using a Nafion and isopropanol mixture, other mediums could be used, such as a Nafion and ethanol mixture, a Nafion and methanol mixture, or a Nafion and water mixture. The specific medium used could influence the properties of the resulting (Fe.Math.Co).sub.9S.sub.8 pentlandite, such as its dispersion stability and electrochemical activity.

[0084] Variations in Electrochemical Measurement Conditions: The conditions under which the electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite is measured could be varied. Instead of using 1 M KOH, other concentrations of KOH could be used, such as 0.5 M KOH, 1.5 M KOH, or 2 M KOH. Additionally, other types of electrolytes could be used, such as sodium hydroxide (NaOH) or potassium chloride (KCl). The specific conditions used could influence the measured electrochemical activity of the (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0085] The bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite described in this disclosure can be used for various applications other than as an electrocatalyst for OER in water splitting for hydrogen production. The sections below describe alternative applications of bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite.

[0086] Water Purification Systems: The bimetallic (Fe.Math.Co).sub.9S.sub.8 pentlandite synthesized through the disclosed method could be used in water purification systems. The electrocatalytic properties of the pentlandite could be utilized to drive electrochemical reactions that break down harmful pollutants in water, such as organic compounds or heavy metals. The high efficiency and stability of the pentlandite could make it a valuable component in water treatment facilities or portable water purification devices.

[0087] Energy Storage Devices: The synthesized (Fe.Math.Co).sub.9S.sub.8 pentlandite could be applied in energy storage devices, such as batteries or supercapacitors. The material's high electrochemical activity could enhance the energy storage capacity and efficiency of these devices. This could be particularly beneficial in the development of renewable energy storage systems, where efficient and cost-effective storage solutions are in high demand.

[0088] Fuel Cells: The (Fe.Math.Co).sub.9S.sub.8 pentlandite could be used as a catalyst in fuel cells, particularly in hydrogen fuel cells. The material's high electrochemical activity towards the oxygen evolution reaction could enhance the efficiency of the fuel cell's operation, potentially improving the overall performance and lifespan of the fuel cell.

[0089] Chemical Industry: The method for synthesizing bimetallic ((Fe.Math.Co).sub.9S.sub.8 pentlandite could be applied in the chemical industry for various reactions that require catalysts. The high catalytic activity and stability of the pentlandite could enhance the efficiency of these reactions, potentially reducing the cost and environmental impact of chemical production processes.

[0090] Environmental Monitoring: The (Fe.Math.Co).sub.9S.sub.8 pentlandite could be used in environmental monitoring devices to detect the presence of specific chemicals or pollutants. The material's electrochemical activity could be utilized to generate a measurable response when exposed to a target substance, providing a means of detecting and quantifying the substance in the environment.

[0091] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

[0092] Since many modifications, variations, and changes in detail can be made to the described embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Furthermore, it is understood that any of the features presented in the embodiments may be integrated into any of the other embodiments unless explicitly stated otherwise. The scope of the invention should be determined by the appended claims and their legal equivalents.

[0093] In addition, the present invention has been described with reference to embodiments, it should be noted and understood that various modifications and variations can be crafted by those skilled in the art without departing from the scope and spirit of the invention. Accordingly, the foregoing disclosure should be interpreted as illustrative only and is not to be interpreted in a limiting sense. Further it is intended that any other embodiments of the present invention that result from any changes in application or method of use or operation, method of manufacture, shape, size, or materials which are not specified within the detailed written description or illustrations contained herein are considered within the scope of the present invention.

[0094] Insofar as the description above and the accompanying drawings disclose any additional subject matter that is not within the scope of the claims below, the inventions are not dedicated to the public and the right to file one or more applications to claim such additional inventions is reserved.

[0095] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.