A high temperature proton exchange membrane and a process for its fabrication thereof

Abstract

The present disclosure relates to a high temperature proton exchange membrane and a process for its fabrication thereof. The high temperature proton exchange membrane comprising: a) polyvinylpyrrolidone (PVP) having a weight-average molecular weight in the range of 2,70,000 to 4,00,000 grams per mole (g / mol); b) polyethersulfone (PES) having a weight-average molecular weight in the range of 25,000 to 65,000 grams per mole (g / mol); and c) silicotungstic acid (SiWA); wherein the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is in the range of 1:1 to 4:1; wherein polyethersulfone (PES) has a degree of sulfonation in the range of 30% to 100%; wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 15 wt% with respect to the total weight of the high temperature proton exchange membrane; wherein the silicotungstic acid (SiWA) is uniformly distributed throughout the matrix of PVP–PES crosslinked polymer.

Description

TECHNICAL FIELDThe present disclosure relates to a proton exchange membrane for fuel cells (PEMFCs), and in particularto a high-temperature proton exchange membrane for fuel cells (HT-PEMFCs), and a process for itsfabrication.BACKGROUNDIn the modern era, electricity is essential for supporting everyday life and driving technologicaladvancement. Currently, a significant portion of electricity is generated from fossil fuels such as coal,oil, natural gas, and nuclear energy. These sources are non-renewable and cause serious environmentalconcerns. In contrast, renewable energy sources-such as solar, wind, biomass, and hydrothermal-offer cleaner alternatives for electricity generation. However, the power produced from these sources isoften intermittent and unstable.Electrochemical technologies, particularly proton exchange membrane fuel cells (PEMFCs), present apromising alternative due to their high efficiency and environmentally friendly operation, producingonly water as a byproduct. Low-temperature PEMFCs (LT-PEMFCs), which operate below 100°C, facechallenges such as carbon monoxide (CO) catalyst poisoning and cathode flooding from liquid wateraccumulation. High-temperature PEMFCs (HT-PEMFCs), operating in the 100-200°C range,overcome these issues by enhancing catalyst tolerance, simplifying thermal management, and utilizingsingle-phase water vapor, thereby improving overall performance.The main difference between the LT-PEMFC and HT-PEMFC is the proton exchange membranes(PEM), which separate oxidants and fuels and transport only hydrogen ions. In PEMFCs, PEMs playcrucial role, including transferring hydrogen ions from the anode to the cathode, separating inlet flowgases, and supporting catalysts at the electrodes. PEMs must possess low permeability to the inlet fuel,good water retention properties, be fabricated from low-cost materials, be easy to synthesize, and behighly durable and stable. Perfluorosulfonic acid (PFSA) based polymer membranes, particularlyNafion membranes, have been extensively studied for PEMFCs applications due to their remarkabledurability and proton-conducting capabilities. However, PFSA based membranes have limitations, suchas decreased efficiency at temperatures above 80°C, as water evaporation reduces hydrogen ionconductivity. Modified perfluoro sulfonic acid, sulfonated hydrocarbon (SHP), and polybenzimidazole(PBI) based membranes attributed promising results for HT-PEMFC applications, as they areaffordable, thermally stable, exhibit excellent oxidation and chemical stability at elevated temperatures.The phosphoric acid-doped (PA -PBI) membrane exhibits high absorption capacity, cost-effectivenesscompared to Nafion membrane, and impermeability to fuel gases and methanol, eliminating the needfor humidification in proton conduction mechanism. However, the monomers required for synthesizingthe PBI polymer, such as 3,3'-diaminobenzidine, are carcinogenic and expensive. The price of the PBIpolymer is also higher than other hydrocarbon-based polymers because its fabrication requires twocomplex synthesis processes. Therefore, it is crucial to develop and characterize PEM membranes withsuperior properties such as high thermal stability, excellent proton conductivity, strong chemicalresistance, and long-term durability at elevated temperatures. The present invention addresses thesechallenges by providing a high-performance PEM membrane that meets all these requirements,ensuring efficient and stable operation in high-temperature fuel cell applications.Reference may be made to the following:Publication No. CN103715438B discusses the fabrication of a nanocomposite proton exchangemembrane composed of sulfonated polyether ether ketone (SPEEK) and polydopamine-modifiedgraphene oxide (PDA-GO). The PDA-GO is first dispersed in dimethylformamide (DMF) ordimethylacetamide (DMAc), followed by ultrasonication for 1 hour and thorough stirring at roomtemperature. SPEEK is then added to this solution to form a casting solution, maintaining aSPEEK:PDA-GO mass ratio of 100:10-202:5 and a solvent-to-polymer mass ratio of 8-10:1. Theresulting mixture is cast onto a glass plate, dried at 60°C for 12 hours, and further dried at 80°C foranother 12 hours to yield a uniform nanocomposite membrane. The resulting membrane demonstrateshigh chemical stability, enhanced proton conductivity, and long-term operational durability underanhydrous conditions up to 120°C, making it highly suitable for proton exchange membrane fuel cellapplications.Publication No. CN102443183A relates the preparation of a high-temperature proton exchangemembrane by doping polybenzimidazole (PBI) with sulfonated cerium phenylphosphinate (CeSPP).CeSPP is uniformly dispersed in a PBI solution, cast onto a stainless-steel plate, and dried under vacuumat 80-120°C for 0.5-4 hours. The cast film is then rapidly frozen in liquid nitrogen (-60 to -80°C) for0.1-5 minutes and soaked in pure water for 3-24 hours before being peeled off. The resultingmembrane, containing 10-40 wt% CeSPP, undergoes phosphoric acid removal to yield the final product.The CeSPP additive, with a sulfonation degree of 100-200%, significantly lowers the proton conductionactivation energy and enhances membrane conductivity-reaching up to 140 mS / cm at 160°C. Thismembrane exhibits excellent thermal and electrochemical performance, making it suitable for hightemperature fuel cells and electrolysis applications.Publication No. US12291615B2 relates to a proton exchange membrane composed of a crystallinesulfonated polyimide block copolymer, defined by a specific structure where Ar₁ is an aromatic groupwith a naphthyl unit, Ar₂ contains at least one sulfonate group, and structural parameters x, m, and nrange from 5-100, 1-200, and 5-500, respectively. The membrane is synthesized via blockcopolymerization, leveraging both the crystallinity and ionic functionality of the polyimide segments.The resulting membrane exhibits exceptional thermal stability and consistent electrochemicalperformance. Notably, the single cell assembled with this membrane maintains a high peak powerdensity of 807 mW / cm2 at operating temperatures up to 110°C, with minimal sensitivity tohumidification. This makes the membrane highly suitable for use in high-performance, hightemperature fuel cell applicationsPublication No. CN110380091A relates to a preparation method for a high-temperature protonexchange membrane composed of phosphoric acid-doped polybenzimidazole (PBI) modified with nanotricalcium phosphate (TCP). The process begins with synthesizing the PBI polymer through hightemperature polymerization of a benzimidazole monomer in polyphosphoric acid. The resultingpolymer is pulverized and dissolved in methanesulfonic acid, followed by the addition of nano TCP asa functional modifier. The mixture is cast onto a substrate using a membrane scraper, and a residualsolvent is evaporated at elevated temperatures to yield a transparent or opaque yellow-brownmembrane. TCP, typically used in biomedical applications, acts here to enhance the membrane's protonconductivity and mechanical stability due to its nanoscale dispersion and interaction with the polymermatrix. The overall process is straightforward, scalable, and integrates multiple modificationtechniques, including acid doping, inorganic filler reinforcement, and cross-linking, making it wellsuited for high-temperature fuel cell applications.Polymers such as polybenzimidazole (PBI), polyimide, and polyether ether ketone (PEEK) are widelyemployed in the fabrication of high-temperature proton exchange membranes due to their inherentproton conductivity, typically fabricated via phase inversion or solution casting with optimized dryingmethods. However, PBI synthesis involves carcinogenic and costly monomers like 3,3'-diaminobenzidine and requires complex multistep fabrication steps, leading to higher production costscompared to other hydrocarbon-based polymers. Moreover, materials such as polyimide and PEEKsuffer from structural degradation at temperatures exceeding 120°C, limiting their long-term thermalstability.Thus, in the light of above limitations of the prior art, there exists a need for a proton exchangemembrane that is thermally stable, is capable of delivering enhanced power density, and has highproton-conductivity at high-temperatures, making it well-suited for its applications in fuel celloperations at high-temperature.OBJECTIVESThe main objective of the present disclosure is to provide a high-temperature proton exchangemembrane for fuel cells (HTPEMFC).Another objective of the present disclosure is to provide a proton exchange membrane having animproved thermal stability and proton conductivity at high temperatures, and which is well-suited forapplications in fuel cells operating at high-temperatures.Yet another objective of the present disclosure is to provide defect-free proton exchange membrane.Yet another objective of the present disclosure is to provide a proton exchange membrane, as analternative to conventional fluorine-based perfluorosulfonic acid (PFSA) membranes that use harmfulfluorinated compounds, for the promotion of environmental sustainability and minimization of healthand ecological risks.Yet another objective of the present disclosure is to provide a process for fabricating a high-temperatureproton exchange membrane for fuel cells (HTPEMFC).Yet another objective of the present disclosure is to provide a process for fabricating a high-temperatureproton exchange membrane for fuel cells (HTPEMFC) that is reliable and scalable.Yet another objective of the present disclosure is to provide a process for fabricating a high-temperatureproton exchange membrane for fuel cells (HTPEMFC) that uses nanomaterials including nanoparticlefillers or crosslinkers.Yet another objective of the present disclosure is to provide a process for fabricating a high-temperatureproton exchange membrane for fuel cells (HTPEMFC) that is efficient, economic and environmentallyfriendly.Yet another objective of the present disclosure is to provide a process for fabricating a high-temperatureproton exchange membrane for fuel cells (HTPEMFC) that is cost-effective, commercially viable,aligning with global efforts toward climate control and helps development of affordable, sustainableenergy solutions.SUMMARYIn an aspect, the present disclosure relates to a high temperature proton exchange membranecomprising:a) polyvinylpyrrolidone (PVP) having a weight-average molecular weight in the range of 2,70,000to 4,00,000 grams per mole (g / mol);b) polyethersulfone (PES) having a weight-average molecular weight in the range of 25,000 to65,000 grams per mole (g / mol); andc) silicotungstic acid (SiWA);wherein the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is in the range of 1:1to 4:1;wherein polyethersulfone (PES) has a degree of sulfonation in the range of 30% to 100%;wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 15 wt% with respect to thetotal weight of the high temperature proton exchange membrane;wherein the silicotungstic acid (SiWA) is uniformly distributed throughout the matrix of PVP-PEScrosslinked polymer; andwherein the high temperature proton exchange membrane is characterized by having elastic modulus inthe range from 31 MPa to 44 MPa, and glass transition temperature (Tg) ≈ 175°C.In another aspect, the present disclosure relates to a process for fabrication of a high temperature protonexchange membrane, said process comprising the following steps:a) dissolving polyvinylpyrrolidone (PVP) and polyethersulfone (PES), in weight ratio in the rangeof 1:1 to 4;1, in N-methyl-2-pyrrolidone (NMP) to obtain a polymeric solution; wherein theratio of total weight of polyvinylpyrrolidone (PVP) and polyethersulfone (PES) to the totalweight of the polymeric solution, is in the range of 5 to 10;b) adding 1 to 15 wt% silicotungstic acid (SiWA) to the polymeric solution, and subjecting theresulting suspension to sonication for 1 hour to obtain a homogenous solution; wherein the wt%of silicotungstic acid is with respect to the total weight of the homogenous solution; andc) casting the homogenous solution onto a substrate and drying the cast solution at a temperaturein the range of 70°C to 90°C for 18 to 30 hours, and then at a temperature in the range of 110°C to 130°C for 4 to 8 hours, to obtain the high temperature proton exchange membrane havingan average thickness in the range of 50 μm to 70 μm.BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGSFigure 1: illustrates the schematic diagram of the process of the present invention for preparation of theproton exchange membrane from the PVP-PES polymer blend.Figure 2: illustrates scanning electron microscopy (SEM) micrographs at 10,000x magnification of (a)the surface and (c) cross-section and energy-dispersive X-ray (EDX) analysis of (b) the surface and (d)cross-section of the proton exchange membrane of the present invention prepared according to theprocess of the present invention.Figure 3: illustrates the FTIR spectral analysis of PA / PVP-PES membrane, PVP-PES / SiWA membrane,PVP-PES membrane, and SiWA.Figure 4: illustrates the comparative study of the proton exchange membrane of the present inventionprepared using 0 - 15% SiWA, by TGA analysis.Figure 5: illustrates the comparative study of the mechanical properties of proton exchange membraneof the present invention prepared according to the process of the present invention: a) without PAdoping, b) with PA doping.Figure 6: illustrates (a) PA acid uptake and (b) swelling ratio of the proton exchange membrane of thepresent invention prepared using 0 - 15% SiWA.Figure 7: illustrates the comparative study of the proton conductivity of the proton exchange membraneof the present invention prepared using 0 - 15% SiWA.Figure 8: illustrates the comparative study of the proton conductivity of the proton exchange membraneof the present invention prepared using 0 - 15% SiWA for (a) variation of its activation energy withtemperature and (b) probable mechanism of proton conduction.Figure 9: illustrates the polarization curves of the proton exchange membrane of the present inventionprepared using 0 - 10% SiWA.Figure 10: illustrates (a) Nyquist plot and (b) performance curve of the proton exchange membrane ofthe present invention prepared using 0 - 15% SiWA, at various temperatures.Figure 11: illustrates (a) durability and (b) hydrogen permeability of the proton exchange membrane ofthe present invention.Figure 12: illustrates (a) ohmic resistance and (b) proton conductivity of the proton exchange membraneof the present invention, evaluated at 140°C over a continuous period of 10 hours.Figure 13: illustrates a comparative analysis of the maximum power densities reported for various HTPEM composite membranes.DETAILED DESCRIPTIONThe following description, with reference to the accompanying drawings, is provided to assist in acomprehensive understanding of exemplary embodiments of the invention. It includes various specificdetails to assist in that understanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize that various changes and modifications ofthe embodiments described herein can be made without departing from the scope of the invention. Inaddition, descriptions of well-known functions and constructions are omitted for clarity andconciseness.The terms and words used in the following description and claims are not limited to the bibliographicalmeanings but are merely used by the inventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in the art that the following description ofexemplary embodiments of the present invention are provided for illustration purpose only and not forthe purpose of limiting the scope of the invention as defined by the appended claims and theirequivalents.Reference in this specification to "one embodiment" or "an embodiment" means that a particularfeature, structure, or characteristic described in connection with the embodiment is included in at leastone embodiment of the present disclosure. The appearance of the phrase "in an embodiment" in variousplaces in the specification does not necessarily all refer to the same embodiment, nor are separate oralternative embodiments mutually exclusive of other embodiments. Moreover, various features aredescribed which may be exhibited by some embodiments and not by others. Similarly, variousrequirements are described which may be requirements for some embodiments but not for otherembodiments.Moreover, although the following description contains many specifics for the purposes of illustration,anyone skilled in the art will appreciate that many variations and / or alterations to said details are withinthe scope of the present disclosure. Similarly, although many of the features of the present disclosureare described in terms of each other, or in conjunction with each other, one skilled in the art willappreciate that many of these features can be provided independently of other features. Accordingly,this description of the present disclosure is set forth without any loss of generality too and withoutimposing limitations upon the present disclosure.The terms "comprises," "comprising," or any other variations thereof are intended to cover a nonexclusive inclusion, such that a process or method that comprises a list of steps does not include onlythose steps but may include other steps not expressly listed or inherent to such process or method.Similarly, one or more devices or sub-systems or elements or structures proceeded by "comprises... a"does not, without more constraints, preclude the existence of other devices or other sub-systems or otherelements or other structures or additional devices or additional sub-systems or additional elements oradditional structures.It is to be understood that the singular forms "a," "an," and "the" include plural referents unless thecontext clearly dictates otherwise.Unless otherwise defined, all technical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which this disclosure belongs. The apparatus,system, and examples provided herein are illustrative only and not intended to be limiting.Polymers such as polybenzimidazole (PBI), polyimide, and polyether ether ketone (PEEK) are widelyemployed in the fabrication of high-temperature proton exchange membranes due to their inherentproton conductivity, typically fabricated via phase inversion or solution casting with optimized dryingmethods. However, PBI synthesis involves carcinogenic and costly monomers like 3,3'-diaminobenzidine and requires complex multistep fabrication steps, leading to higher production costscompared to other hydrocarbon-based polymers. Moreover, materials such as polyimide and PEEKsuffer from structural degradation at temperatures exceeding 120°C, limiting their long-term thermalstability.To address these limitations, the present invention introduces a thermally robust, high protonconducting membrane capable of delivering enhanced power density under high-temperature fuel celloperating conditions.Therefore, in an aspect, the present disclosure relates to a high temperature proton exchange membranecomprising:a) polyvinylpyrrolidone (PVP) having a weight-average molecular weight in the range of 2,70,000to 4,00,000 grams per mole (g / mol);b) polyethersulfone (PES) having a weight-average molecular weight in the range of 25,000 to65,000 grams per mole (g / mol); andc) silicotungstic acid (SiWA);wherein the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is in the range of 1:1to 4:1;wherein polyethersulfone (PES) has a degree of sulfonation in the range of 30% to 100%;wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 15 wt% with respect to thetotal weight of the high temperature proton exchange membrane;wherein the silicotungstic acid (SiWA) is uniformly distributed throughout the matrix of PVP-PEScrosslinked polymer; andwherein the high temperature proton exchange membrane is characterized by having elastic modulus inthe range from 31 MPa to 44 MPa, and glass transition temperature (Tg) ≈ 175°C.In an embodiment of the present disclosure, the polyvinylpyrrolidone (PVP) has a weight-averagemolecular weight in the range of 3,00,000 to 3,50,000 grams per mole (g / mol).In another embodiment of the present disclosure, the polyvinylpyrrolidone (PVP) has a weight-averagemolecular weight in the range of 3,00,000 to 3,45,000 grams per mole (g / mol).In a preferred embodiment of the present disclosure, the polyvinylpyrrolidone (PVP) has a weightaverage molecular weight in the range of 3,00,000 to 3,40,000 grams per mole (g / mol).In a more preferred embodiment of the present disclosure, the polyvinylpyrrolidone (PVP) has a weightaverage molecular weight in the range of 3,10,000 to 3,30,000 grams per mole (g / mol).In a most preferred embodiment of the present disclosure, the polyvinylpyrrolidone (PVP) has a weightaverage molecular weight of 3,20,000 grams per mole (g / mol).In an embodiment of the present disclosure, the polyethersulfone (PES) has a weight-average molecularweight in the range of 25,000 to 65,000 grams per mole (g / mol).In another embodiment of the present disclosure, the polyethersulfone (PES) has a weight-averagemolecular weight in the range of 30,000 to 60,000 grams per mole (g / mol).In a preferred embodiment of the present disclosure, the polyethersulfone (PES) has a weight-averagemolecular weight in the range of 35,000 to 55,000 grams per mole (g / mol).In a more preferred embodiment of the present disclosure, independently, the polyethersulfone (PES)has a weight-average molecular weight in the range of 40,000 to 50,000 grams per mole (g / mol).In a most preferred embodiment of the present disclosure, the polyethersulfone (PES) has a weightaverage molecular weight of 45,000 grams per mole (g / mol).In an embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone (PVP) topolyethersulfone (PES) is in the range of 1:1 to 4:1.In another embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone (PVP) topolyethersulfone (PES) is in the range of 1.1:1 to 3.5:1.In a preferred embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone (PVP) topolyethersulfone (PES) is in the range of 1.2:1 to 3:1.In a more preferred embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone(PVP) to polyethersulfone (PES) is in the range of 1.3:1 to 2.5:1.In a most preferred embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone(PVP) to polyethersulfone (PES) is in the range of 1.4:1 to 1.6:1.In a yet most preferred embodiment of the present disclosure, the weight ratio of polyvinylpyrrolidone(PVP) to polyethersulfone (PES) is 3 to 2.In an embodiment of the present disclosure, the polyethersulfone (PES) has a degree of sulfonation inthe range of 30 % to 100 %.In another embodiment of the present disclosure, the polyethersulfone (PES) has a degree of sulfonationin the range of 40% to 90%.In a preferred embodiment of the present disclosure, the polyethersulfone (PES) has a degree ofsulfonation in the range of 50% to 80%.In a more preferred embodiment of the present disclosure, the polyethersulfone (PES) has a degree ofsulfonation in the range of 60 % to 70%.In a most preferred embodiment of the present disclosure, the polyethersulfone (PES) has a degree ofsulfonation of 65 %.In an embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is in the rangefrom 1 to 15 wt% with respect to the total weight of the high temperature proton exchange membrane.In another embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is in therange from 1 to 14 wt% with respect to the total weight of the high temperature proton exchangemembrane.In a preferred embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is in therange from 1 to 13 wt% with respect to the total weight of the high temperature proton exchangemembrane.In a more preferred embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) isin the range from 1 to 12 wt% with respect to the total weight of the high temperature proton exchangemembrane.In a most preferred embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is1 to 11 wt% with respect to the total weight of the high temperature proton exchange membrane.In another most preferred embodiment of the present disclosure, the amount of silicotungstic acid(SiWA) is 1 to 10 wt% with respect to the total weight of the high temperature proton exchangemembrane.In a yet another most preferred embodiment of the present disclosure, the amount of silicotungstic acid(SiWA) is 10 wt% with respect to the total weight of the high temperature proton exchange membrane.In an embodiment of the present disclosure, the silicotungstic acid (SiWA) is uniformly distributedthroughout the matrix of PVP-PES crosslinked polymer.In an embodiment of the present disclosure, the high temperature proton exchange membrane ischaracterized by having elastic modulus in the range from 31 MPa to 44 MPa, and glass transitiontemperature (Tg) ≈ 175°C.In another embodiment of the present disclosure, the high temperature proton exchange membrane ischaracterized by having elastic modulus of 44 MPa, and glass transition temperature (Tg) ≈ 175°C.In an embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is in the rangefrom 1 to 10 wt%, the membrane is characterized by having a proton conductivity (σ) in the range from37 mS / cm to 60 mS / cm at 140°C under anhydrous conditions.In an embodiment of the present disclosure, the amount of silicotungstic acid (SiWA) is 10 wt%, andthe membrane is characterized by having proton conductivity (σ) of 58 mS / cm at 140°C underanhydrous conditions.In an embodiment of the present disclosure, the membrane has a thickness in the range of 50 μm to 70μm.In another embodiment of the present disclosure, the membrane has a thickness in the range of 52 μmto 68 μm.In a preferred embodiment of the present disclosure, the membrane has a thickness in the range of 54μm to 66 μm.In a more preferred embodiment of the present disclosure, the membrane has a thickness in the rangeof 56 μm to 64 μm.In a most preferred embodiment of the present disclosure, the membrane has a thickness in the range of58 μm to 62 μm.In a yet most preferred embodiment of the present disclosure, the membrane has a thickness of 70 μm.In another aspect, the present disclosure relates to a process for fabrication of a high temperature protonexchange membrane, said process comprising the following steps:a) dissolving polyvinylpyrrolidone (PVP) and polyethersulfone (PES), in a weight ratio in therange of 1:1 to 4:1, in N-methyl-2-pyrrolidone (NMP) to obtain a polymeric solution; whereinthe ratio of total weight of polyvinylpyrrolidone (PVP) and polyethersulfone (PES) to the totalweight of the polymeric solution, is in the range of 5 to 10 wt%;b) adding 1 to 15 wt% silicotungstic acid (SiWA) to the polymeric solution, and subjecting theresulting suspension to sonication for 1 hour to obtain a homogenous solution; wherein the wt%of silicotungstic acid is with respect to the total weight of the homogenous solution; andc) casting the homogenous solution onto a substrate and drying the cast solution at a temperaturein the range of 70°C to 90°C for 18 to 30 hours, and then at a temperature in the range of 110°C to 130°C for 4 to 8 hours, to obtain the high temperature proton exchange membrane havingan average thickness in the range of 50 μm to 70 μm.In an embodiment of the present disclosure, in step (a), the weight ratio of polyvinylpyrrolidone (PVP)and polyethersulfone (PES) in the polymeric solution is in the range of 1:1 to 4:1.In another embodiment of the present disclosure, in step (a), the weight ratio of polyvinylpyrrolidone(PVP) and polyethersulfone (PES) in the polymeric solution is in the range of 1.1:1 to 3.5:1.In a preferred embodiment of the present disclosure, in step (a), the weight ratio of polyvinylpyrrolidone(PVP) and polyethersulfone (PES) in the polymeric solution is in the range of 1.2:1 to 3:1.In a more preferred embodiment of the present disclosure, in step (a), the weight ratio ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) in the polymeric solution is in the range of1.3:1 to 2.5:1.In a most preferred embodiment of the present disclosure, in step (a), the weight ratio ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) in the polymeric solution is in the range of1.4:1 to 1.6:1.In a yet most preferred embodiment of the present disclosure, in step (a), the weight ratio ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) in the polymeric solution is 3 to 2.In an embodiment of the present disclosure, in step (a), the total combined weight ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) is in the range of 5 to 10 wt% of the totalweight of the polymeric solution.In another embodiment of the present disclosure, in step (a), the total combined weight ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) is in the range of 5 to 9 wt% of the total weightof the polymeric solution.In a preferred embodiment of the present disclosure, in step (a), the total combined weight ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) is in the range of 5 to 8 wt% of the total weightof the polymeric solution.In a more preferred embodiment of the present disclosure, in step (a), the total combined weight ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) is in the range of 6 to 8 wt% of the total weightof the polymeric solution.In a most preferred embodiment of the present disclosure, in step (a), the total combined weight ofpolyvinylpyrrolidone (PVP) and polyethersulfone (PES) is 7 wt% of the total weight of the polymericsolution.In an embodiment of the present disclosure, in step (a), the polyvinylpyrrolidone (PVP) has a weightaverage molecular weight in the range of 3,00,000 to 3,50,000 grams per mole (g / mol).In another embodiment of the present disclosure, in step (a), the polyvinylpyrrolidone (PVP) has aweight-average molecular weight in the range of 3,00,000 to 3,45,000 grams per mole (g / mol).In a preferred embodiment of the present disclosure, in step (a), the polyvinylpyrrolidone (PVP) has aweight-average molecular weight in the range of 3,00,000 to 3,40,000 grams per mole (g / mol).In a more preferred embodiment of the present disclosure, in step (a), the polyvinylpyrrolidone (PVP)has a weight-average molecular weight in the range of 3,10,000 to 3,30,000 grams per mole (g / mol).In a most preferred embodiment of the present disclosure, in step (a), the polyvinylpyrrolidone (PVP)has a weight-average molecular weight of 3,20,000 grams per mole (g / mol).In an embodiment of the present disclosure, in step (a), the polyethersulfone (PES) has a degree ofsulfonation in the range of 30 % to 100 %.In another embodiment of the present disclosure, in step (a), the polyethersulfone (PES) has a degreeof sulfonation in the range of 40 % to 90 %.In a preferred embodiment of the present disclosure, in step (a), the polyethersulfone (PES) has a degreeof sulfonation in the range of 50 % to 80 %.In a more preferred embodiment of the present disclosure, in step (a), the polyethersulfone (PES) has adegree of sulfonation in the range of 60 % to 70 %.In a most preferred embodiment of the present disclosure, in step (a), the polyethersulfone (PES) has adegree of sulfonation of 65 %.In an embodiment of the present disclosure, the polyethersulfone (PES) has a weight-average molecularweight in the range of 25,000 to 65,000 grams per mole (g / mol).In another embodiment of the present disclosure, the polyethersulfone (PES) has a weight-averagemolecular weight in the range of 30,000 to 60,000 grams per mole (g / mol).In a preferred embodiment of the present disclosure, the polyethersulfone (PES) has a weight-averagemolecular weight in the range of 35,000 to 55,000 grams per mole (g / mol).In a more preferred embodiment of the present disclosure, the polyethersulfone (PES) has a weightaverage molecular weight in the range of 40,000 to 50,000 grams per mole (g / mol).In a most preferred embodiment of the present disclosure, the polyethersulfone (PES) has a weightaverage molecular weight in the range of 45,000 grams per mole (g / mol).In an embodiment of the present disclosure, in step (b), adding 1 to 15 wt% silicotungstic acid (SiWA)to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hour to obtain ahomogenous solution; wherein the wt% of silicotungstic acid is with respect to the total weight of thehomogenous solution.In another embodiment of the present disclosure, in step (b), adding 3 to 14 wt% silicotungstic acid(SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hour toobtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the total weightof the homogenous solution.In a preferred embodiment of the present disclosure, in step (b), adding 5 to 13 wt% silicotungstic acid(SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hour toobtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the total weightof the homogenous solution.In a more preferred embodiment of the present disclosure, in step (b), adding 7 to 12 wt% silicotungsticacid (SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hourto obtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the totalweight of the homogenous solution.In a most preferred embodiment of the present disclosure, in step (b), adding 9 to 11 wt% silicotungsticacid (SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hourto obtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the totalweight of the homogenous solution.In a yet most preferred embodiment of the present disclosure, in step (b), adding 10 wt% silicotungsticacid (SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hourto obtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the totalweight of the homogenous solution.In an embodiment of the present disclosure, in step (c), casting the homogenous solution onto a substrateand drying the cast solution at a temperature in the range of 70°C to 90°C for 18 to 30 hours, and thenat a temperature in the range of 110°C to 130°C for 4 to 8 hours.In another embodiment of the present disclosure, in step (c), casting the homogenous solution onto asubstrate and drying the cast solution at a temperature in the range of 72°C to 88°C for 19 to 29 hours,and then at a temperature in the range of 112°C to 128°C for 4.5 to 7.5 hours.In a preferred embodiment of the present disclosure, in step (c), casting the homogenous solution ontoa substrate and drying the cast solution at a temperature in the range of 74°C to 86°C for 20 to 28hours, and then at a temperature in the range of 114°C to 126°C for 5 to 7 hours.In a more preferred embodiment of the present disclosure, in step (c), casting the homogenous solutiononto a substrate and drying the cast solution at a temperature in the range of 76°C to 84°C for 21 to 27hours, and then at a temperature in the range of 116°C to 124°C for 5.5 to 6.5 hours.In a most preferred embodiment of the present disclosure, in step (c), casting the homogenous solutiononto a substrate and drying the cast solution at a temperature in the range of 78°C to 82°C for 22 to 26hours, and then at a temperature in the range of 118°C to 122°C for 6 to 7 hours.In a yet most preferred embodiment of the present disclosure, in step (c), casting the homogenoussolution onto a substrate and drying the cast solution at a temperature of 80°C for 24 hours, and thenat a temperature of 120°C for 6 hours.In an embodiment of the present disclosure, in step (c), further comprising a step of immersing themembrane in phosphoric acid (PA, 85 wt%) at room temperature for 24 hours, and then at 80°C foranother 24 hours to obtain a PA doped high temperature proton exchange membrane.The PVP-PES / 10 %SiWA nanocomposite membrane exhibits higher conductivity of up to 58 mS / cmat 140°C, as compared to the conductivity of 37 mS / cm for the pristine PVP-PES membrane. Thus,incorporation of 10% SiWA into PVP-PES matrix results in 55% increment in its conductivity.In PVP-PES / SiWA composite membranes, the activation energy decreases as the concentration ofSiWA increases, from 15 kJ / mol for the pristine PVP-PES membrane to 10 kJ / mol for the 10% SiWAnanocomposite membrane. This reduction in activation energy can be attributed to the enhancedinteraction between the SiWA nanoparticles and the polymer matrix, which facilitates faster mobilityof the polymer chains. Lower energy activation typically indicates that a fast electrochemical process.The pristine PVP-PES membrane exhibited limited electrochemical performance, achieving a peakpower density of 350 mW / cm2. However, on incorporation of silicotungstic acid (SiWA) into the PVP-PES matrix significantly enhanced the fuel cell performance. The resulting PVP-PES / 10 wt% SiWAnanocomposite membrane achieved a peak power density of 630 mW / cm2 under the same operatingconditions, representing an 80% increase compared to the pristine PVP-PES membrane. Thisimprovement indicates that the nanocomposite structure provides additional pathways for protonconduction, thereby enhancing the overall proton transport and cell efficiency.At an operating voltage of 0.6 V, the current density of PVP-PES-10 wt% SiWA composite membranewas observed to be 400 mA / cm2 at 120°C, increasing to 450 mA / cm2 at 140°C, and further rising to500 mA / cm2 at 160°C, indicating enhanced electrochemical kinetics with temperature. However, adecline in current density to 470 mA / cm2 was noted at 180°C. This sudden drop in performance isattributed to the onset of thermal degradation of the membrane structure, likely due to exceeding itsglass transition temperature (Tg ≈ 175°C).The pristine PVP-PES membrane shows an elastic modulus of 30 MPa. Incorporating SiWA into thePES-PVP matrix significantly enhances the membrane's mechanical strength. As the SiWA contentincreases from 1 wt% to 15 wt%, the elastic modulus of the composite membranes increasessubstantially, from 31 MPa to 44 MPa.The mechanical properties of the membrane play a critical role in ensuring reliable performance andlong-term durability of HTPEMFCs.The present invention is further illustrated by the following examples. These examples describe possiblepreferred embodiments for illustrative purposes only, but they do not limit the scope of the invention.These laboratory scale experiments can be scaled up to industrial / commercial scale.EXAMPLESThe following examples are given by way of illustration of the present invention and should not beconstrued to limit the scope of present disclosure. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary and explanatory only and are intendedto provide further explanation of the subject matter.Although the subject matter has been described in considerable detail with reference to certain preferredembodiments thereof, other embodiments are possible. As such, the spirit and scope of the subjectmatter should not be limited to the description of the preferred embodiment contained therein.Materials, Methods and MeasurementsChemicals and ReagentsAll commercially available chemicals were purchased from appropriate sources and used as receivedunless otherwise mentioned.Polyvinylpyrrolidone (PVP) was purchased from Otto Chemie Pvt. Ltd., India.Polyethersulfone (PES) was obtained from Tech Inc. Pvt. Ltd., India.Silicotungstic acid (SiWA) was procured from Sisco Research Laboratory Pvt. Ltd, IndiaPhosphoric acid (PA, 85 wt%) was procured from Sisco Research Laboratory Pvt. Ltd, IndiaInstrumentationThe chemical structure of the SiWA / PVP-PES blended membrane was investigated using FourierTransform Infrared (FTIR) Spectroscopy. Analysis was performed on an Agilent 630 instrument in therange of 4000-600 cm-1 at a resolution of 4 cm-1, with 32 scans collected per sample.The surface and cross-sectional morphologies of the composite membrane were examined using fieldemission scanning electron microscopy (FESEM). A Thermo Fisher ASPROW instrument was used ina low-vacuum setting. The elemental composition of the membrane was analyzed with an energydispersive X-ray spectroscopy (EDS) detector from AMETEK.The thermal stability of the composite membranes was analyzed using thermogravimetric analysis(TGA). A NETZSCH TG209 F3 Tarsus (Germany) instrument was used for the analysis. Each sample,weighing approximately 10 mg, was heated from ambient temperature to 800°C at a constant heatingrate of 10°C / min under a nitrogen gas flow of 10 mL / min.The mechanical strength of the composite membranes was assessed using a universal testing machine(UTM), model no. UTM 1000 kgf, from Advanced Equipment. The test samples, measuring 40 mm x10 mm x 0.1 mm, were subjected to a consistent crosshead speed of 100 mm / min. For each data point,five samples were tested, and the recorded average value was considered.Example 1 - Synthesis of High Temperature Proton Exchange Membrane:Polyvinylpyrrolidone (PVP) (Mn = 3,20,000 g / mol) and polyethersulfone (PES) (Mn = 45,000 g / mol)in a weight ratio of 3:2 was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a polymeric solutionwith a total polymer concentration of 7 wt%. Silicotungstic acid (SiWA)-a heteropoly acidnanofiller-was added to the above polymeric solution, and the resulting suspension was subjected tosonication for 1 hour to obtain a homogenous solution. The resulting solution was cast onto a glass Petridish and dried in two steps: at 80°C for 24 hours, then at 120°C for 6 hours. The final membrane hadan average thickness of 60 ± 10 μm.For phosphoric acid doping, membranes were immersed in 85 wt% PA at room temperature for 24hours, then treated at 80°C for another 24 hours to ensure full acid uptake.The fabrication process of the present disclosure is illustrated in Figure 1. The membranesprepared / fabricated according to the process of the present disclosure, were studied for theirmorphologies by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX)spectroscopy. The surface and cross-sectional morphologies, respectively, of the PVP-PES / SiWAnanocomposite membranes are displayed in Figure 2(a) and 2(c). The membranes were found to exhibita dense and uniform microstructure, indicating successful integration of components without defects.The scanning electron microscopy (SEM) micrographs of the composite membranes showed no visibleaggregation, cracks, or phase separation, confirming good dispersion and compatibility within thepolymer matrix. Furthermore, energy-dispersive X-ray (EDX) analysis verifies the presence of Si, O,and W elements in both surface and cross-sectional views, as displayed in Figure 2(b) and 2(d),supporting the uniform distribution of SiWA throughout the membrane.Results and DiscussionCharacterizationFTIR analysisThe chemical structure of the SiWA / PVP-PES composite membrane was analysed by Fourier transforminfrared spectroscopy (FTIR) using at a resolution of 4 cm-1 and wavenumber ranging from 4000-400cm-1. The FTIR spectra of membranes doped with or without heteropolyacid (HPA) and preparedaccording to the process of the present disclosure, clearly display characteristic vibrational modesassociated with each component (Figure 3).The heteropoly acid nanofiller exhibits two prominent absorption bands at 976 cm-1 and 909 cm-1,corresponding to the asymmetric stretching of terminal W=O bonds and the asymmetric stretching ofW-O-W bonds, respectively. The pristine PVP-PES blend membrane displays characteristic peaks at1289 cm-1 and 1650 cm-1, which are assigned to the C-N and C=O stretching vibrations of thepyrrolidone ring in PVP. Additionally, a distinct absorption band at 1148 cm-1 is observed,corresponding to the S=O stretching vibration of the sulfone group in PES. The presence of these peakssuggests strong physicochemical interaction between the SiWA anions and the electron-rich nitrogen(N) and carbonyl oxygen (O) atoms within the PVP component of the membrane. This interaction isexpected to contribute to the enhanced proton transport properties of the composite membrane.TGA analysisThe thermal properties of composite membranes, prepared according to the process of the presentdisclosure, were analyzed by measuring the weight loss as a function of temperature. In the compositemembranes, the weight loss observed at temperatures below 100°C is primarily attributed to theevaporation of absorbed water, as shown in Fig. 4. The PVP polymer remains stable in air up to 300°C, after which it begins to degrade due to the decomposition of the PVP main polymer chain. Incontrast, the PES polymer degrades around 500°C in air. Incorporating SiWA into the compositemembranes enhances the thermal stability of the PES-PVP blend.The mechanical properties of the membrane play a critical role in ensuring reliable performance andlong-term durability of HTPEMFCs. Fig. 5 presents the stress-strain curves of SiWA-x compositemembranes, both before and after PA doping. The pristine PVP-PES membrane shows an elasticmodulus of 30 MPa. Incorporating SiWA into the PES-PVP matrix significantly enhances themembrane's mechanical strength. As the SiWA content increases from 1 wt% to 15 wt%, the elasticmodulus of the composite membranes increases substantially, from 31 MPa to 44 MPa. However, theaddition of PA leads to a dramatic reduction in the mechanical strength of the PA / SiWA-15 membrane,which drops to 4 MPa. This decrease is attributed to swelling within the composite membrane, whichweakens the intermolecular interactions among the polymer chains and results in the presence of freePA molecules within the polymer matrix.The level of acid doping plays a crucial role in increasing ionic conductivity, facilitated by hydrogenbond formation between the basic NH2 base of the amine group and H3PO4 acid. As shown in Fig. 6 theacid doping level increases with the increase in SiWA-x concentration from 1 to 10 wt% as themembrane hydrophilicity increases. The acid doping level rises from 1.8 mol / rep (number of PAmolecules per repeating monomer unit) for SiWA 0% doping to 3.5 mol / rep for SiWA 10 % compositemembrane. However, increases in the acid doping level increase the plasticizer effect due to more freeacid volume inside the membrane backbone chain, which decreases the mechanical strength of themembrane. As the acid doping level increases, the swelling ratio, also increases from 35 % to 61 % byvarying the SiWA concentration from 0 to 10 %. Therefore, to retain the mechanical strength of thecomposite membrane, optimizing the acid doping is very crucial.In evaluating fuel cell performance, a crucial parameter is the proton conductivity of ions, whichsignifies the rate at which protons transfer from the anode to the cathode. This study investigates theproton conductivity of phosphoric-doped membrane samples and nanocomposite-based membranes atroom temperature. Ionic conductivity increases with temperature due to a decrease in energy activation.The PVP-PES / SiWA 10 % nanocomposite membranes exhibit higher conductivity, reaching up to 58mS / cm at 140°C as 37 mS / cm for the pristine membranes therefore 55% increasment in theconductivity, as shown in Fig.7. The increase in proton conductivity is attributed to an increase in theconcentration of charge carriers (H3O+, -PO4, P-O, P-OH) in the nanocomposite membranes. Thesecharge carriers interact with the basic sites of the PVP polymer and heteropoly acid through hydrogenbonds, facilitating proton transport in the nanocomposite membrane and enhancing proton conductivity.The Arrhenius curve (Fig. 8a) shows the temperature dependence of the rate of a chemical process,which requires activation energy. Lower energy activation typically indicates that a fast electrochemicalprocess occurs. In the case of the PVP-PES / SiWA composite membranes, the activation energydecreases as the concentration of SiWA increases, from 15 kJ / mol for the pristine PVP-PES membraneto 10 kJ / mol for the 10% SiWA nanocomposite membrane. This reduction in activation energy can beattributed to the enhanced interaction between the SiWA nanoparticles and the polymer matrix, whichfacilitates faster mobility of the polymer chains. The presence of SiWA acts as a plasticizer, reducingthe energy barrier for molecular motion and thus promoting easier diffusion and improved overallmembrane performance at lower temperatures shown in Fig.8b. The reduction in activation energy isattributed to multiple proton conduction pathways forming in the nanocomposite membrane.Fig. 9 shows the polarization performance of the mixed matrix membranes evaluated under dryconditions at 160°C in a HT-PEMFC. The pristine PVP-PES membrane exhibited limitedelectrochemical performance, achieving a peak power density of 350 mW / cm2. However, theincorporation of silicotungstic acid (SiWA) into the membrane matrix significantly enhanced the fuelcell performance. The resulting PVP-PES / 10 wt% SiWA nanocomposite membrane achieved a peakpower density of 630 mW / cm2 under the same operating conditions, representing an 80% increasecompared to the pristine membrane. This improvement indicates that the nanocomposite structureprovides additional pathways for proton conduction, thereby enhancing the overall proton transport andcell efficiency.The electrochemical reaction rate in fuel cells generally increases with temperature due to a reductionin activation energy. Fig. 10 illustrates the performance curves of the nanocomposite membrane atvarious operating temperatures. At an operating voltage of 0.6 V, the current density was observed tobe 400 mA / cm2 at 120°C, increasing to 450 mA / cm2 at 140°C, and further rising to 500 mA / cm2 at160°C, indicating enhanced electrochemical kinetics with temperature. However, a decline in currentdensity to 470 mA / cm2 was noted at 180°C. This sudden drop in performance is attributed to the onsetof thermal degradation of the membrane structure, likely due to exceeding its glass transitiontemperature (Tg ≈ 175°C). Therefore, the membrane may begin to lose its mechanical integrity andproton-conducting network, compromising its ability to maintain high proton conductivity underelevated thermal stress. This degradation in performance is further confirmed by the Nyquist plot, whichreflects a corresponding reduction in power density of the fuel cell due to increased ohmic and chargetransfer resistances.The nanocomposite membrane also demonstrated good operational durability when tested at a constantcurrent density of 500 mA / cm2 for 60 hours. A degradation rate of approximately 3 mV / h was observed.Initially, a noticeable drop in cell potential occurred, likely due to membrane conditioning or initialstabilization. However, the potential decline stabilized over time, indicating the membrane's ability tomaintain performance under continuous operation, as illustrated in Fig. 11a.Linear sweep voltammetry (LSV) was conducted to evaluate hydrogen crossover through the membraneelectrode assembly (MEA). As shown in Figure 11b, the PVP-PES / SiWA nanocomposite membraneexhibited minimal increase in hydrogen crossover current density even after 12 hours of operation,indicating excellent gas barrier properties and structural stability. However, the pristine membraneshowed a noticeable rise in crossover current density over time, attributed to acid leaching, which leadsto membrane thinning and increased hydrogen permeability. The incorporation of SiWA in thecomposite membrane effectively suppressed acid leaching, thereby enhancing membrane stability andmaking it more suitable for high-temperature PEMFC applications.The proton conductivity of the membrane was evaluated at 140°C over a continuous period of 10 hours.As shown in Fig. 12, a noticeable decrease in ohmic resistance was observed during the initial 1 to 2hours of operation. This reduction can be attributed to the evaporation of loosely bound or freephosphoric acid present on the membrane surface, which may have also led to a slight reduction inmembrane thickness. Consequently, proton conductivity increased from 57 mS / cm to 64 mS / cm duringthis initial phase.Following this, after approximately 6 hours, a slight increase in ohmic resistance was observed. This islikely due to the gradual leaching of phosphoric acid from the membrane matrix. Despite this, themembrane maintained a stable ohmic resistance and proton conductivity beyond the 6-hour mark,indicating good thermal and chemical stability of the membrane under prolonged high-temperatureconditions.These findings suggest that the membrane exhibits stable proton conductivity at 140°C, making itsuitable for high-temperature applications such as Proton Exchange Membrane Fuel Cells (PEMFCs).Furthermore, as shown in Fig. 13, a comparative analysis of the maximum power densities reported forHT-PEM composite membranes confirms that the performance of the PES-PVP-SiWA membrane inthis study is among the highest, reinforcing its suitability as a promising candidate for high-temperaturefuel cell systems.Table 1. Optimum weight concentration of PVP-PES composite membrane.Table 2. Mechanical strength of the fabricated membrane before and after PA doping. Table 3. presents a comparison of various mixed-matrix composite membranes reported in previousstudies, highlighting the proton conductivity and power density achieved under high-temperatureoperating conditions. Numerous modifications and adaptations of the system of the present invention will be apparent to thoseskilled in the art, and thus it is intended by the appended claims to cover all such modifications andadaptations which fall within the true spirit and scope of this invention.TECHNICAL ADVANTAGESThe present disclosure described herein has several technical advantages as follows:- provides a high-temperature proton exchange membrane for fuel cells (HTPEMFC)- provides a nanocomposite membrane having an improved thermal stability and protonconductivity at high temperatures, and which is well-suited for applications in fuel cellsoperating at high-temperatures- provides defect-free nanocomposite membranes.- provides a sustainable membrane, as an alternative to conventional fluorine-basedperfluorosulfonic acid (PFSA) membranes that use harmful fluorinated compounds, for thepromotion of environmental sustainability and minimization health and ecological risks.- provides a process for fabricating high-temperature proton exchange membranes for fuel cells(HTPEMFC).- provides a process for preparing high-temperature proton exchange membranes for fuel cells(HTPEMFC) that is reliable and scalable.- provides a process for preparing proton exchange membranes for high-temperature fuel cells(HTPEMFC) that uses nanomaterials including nanoparticle fillers or crosslinkers.- provides a process for preparing proton exchange membranes for high-temperature fuel cells(HTPEMFC) that is efficient, economic and environmentally friendly.- provides a process for preparing high-temperature proton exchange membranes for fuel cells(HTPEMFC) that is cost-effective, commercially viable, aligning with global efforts towardclimate control and helps development of affordable, sustainable energy solutions.

Claims

1. A high temperature proton exchange membrane comprising: a) polyvinylpyrrolidone (PVP) having a weight-average molecular weight in the range of 2,70,000 to 4,00,000 grams per mole (g / mol); b) polyethersulfone (PES) having a weight-average molecular weight in the range of 25,000 to 65,000 grams per mole (g / mol); and c) silicotungstic acid (SiWA); wherein the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is in the range of 1:1 to 4:1; wherein polyethersulfone (PES) has a degree of sulfonation in the range of 30 % to 100 %; wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 15 wt% with respect to the total weight of the high temperature proton exchange membrane; wherein the silicotungstic acid (SiWA) is uniformly distributed throughout the matrix of PVP- PES composite polymer; and wherein the high temperature proton exchange membrane is characterized by having elastic modulus in the range from 31 MPa to 44 MPa, and glass transition temperature (Tg) ≈ 175 °C.

2. The membrane as claimed in claim 1, wherein the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is 3:

2.

3. The membrane as claimed in claim 1, wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 10 wt%.

4. The membrane as claimed in claim 1, wherein the amount of silicotungstic acid (SiWA) is in the range from 1 to 10 wt%, the membrane being characterized by having a proton conductivity (σ) in the range from 37 mS / cm to 60 mS / cm at 140 °C under anhydrous conditions.

5. The membrane as claimed in claim 1, wherein the amount of silicotungstic acid (SiWA) is 10 wt%, the membrane being characterized by having proton conductivity (σ) of 58 mS / cm at 140 °C under anhydrous conditions.

6. The membrane as claimed in claim 1, wherein the membrane has a thickness in the range of 50 μm to 70 μm.

7. A process for fabrication of high temperature proton exchange membrane, said process comprising the following steps: a) dissolving polyvinylpyrrolidone (PVP) and polyethersulfone (PES), in a weight ratio in the range of 1:1 to 4:1, in N-methyl-2-pyrrolidone (NMP) to obtain a polymeric solution; wherein the ratio of total weight of polyvinylpyrrolidone (PVP) and polyethersulfone (PES) to the total weight of the polymeric solution, is in the range of 5 to 10 wt%; b) adding 1 to 15 wt% silicotungstic acid (SiWA) to the polymeric solution, and subjecting the resulting suspension to sonication for 1 hour to obtain a homogenous solution; wherein the wt% of silicotungstic acid is with respect to the total weight of the homogenous solution; and c) casting the homogenous solution onto a substrate and drying the cast solution at a temperature in the range of 70 °C to 90 °C for 18 to 30 hours, and then at a temperature in the range of 110 °C to 130 °C for 4 to 8 hours, to obtain the high temperature proton exchange membrane having an average thickness in the range of 50 μm to 70 μm.

8. The process as claimed in claim 7, wherein in step (a), the weight ratio of polyvinylpyrrolidone (PVP) to polyethersulfone (PES) is 3 to 2; the total combined weight of polyvinylpyrrolidone (PVP) and polyethersulfone (PES) is 7 wt% of the total weight of the polymeric solution; the polyvinylpyrrolidone (PVP) has a weight-average molecular weight of 3,20,000 grams per mole (g / mol); the polyethersulfone (PES) has a degree of sulfonation in the range of 30% to 100%; and the polyethersulfone (PES) has a weightaverage molecular weight of 45,000 grams per mole (g / mol);.

9. The process as claimed in claim 7, wherein in step (b), the amount of silicotungstic acid is 5 to 10 wt% with respect to the total weight of the homogenous solution.

10. The process as claimed in claim 7, wherein in step (c), further comprising a step of immersing the membrane in phosphoric acid (85 wt%) at room temperature for 24 hours, and then at 80 °C for another 24 hours to obtain a PA doped high temperature proton exchange membrane.