Electrocatalyst for proton exchange memebrane fuel cell and process of prepration thereof

Abstract

The present disclosure generally relates to proton exchange membrane fuel cells (PEMFCs). Specifically, the present disclosure relates to an electrocatalyst comprising combination of M1-metal, M2-metal oxide supported onto a support, wherein the M2 metal oxide is decorated or deposited onto the support, and a process of preparation thereof. The present disclosure also relates to a proton exchange membrane fuel cell comprising said electrocatalyst as coated onto an electrode.

Description

[0001] ELECTROCATALYST FOR PROTON EXCHANGE MEMEBRANE FUEL CELL AND PROCESS OF PREPRATION THEREOF

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present disclosure generally relates to proton exchange membrane fuel cells (PEMFCs). Specifically, the present disclosure relates to electrocatalyst comprising combination of metal Ml and a coated catalyst support and a process of preparation thereof. The present disclosure further relates to a proton exchange membrane fuel cell comprising said electrocatalyst as coated onto an electrode for oxygen reduction reactions at the cathode.

[0004] BACKGROUND OF THE INVENTION

[0005] The proton exchange membrane fuel cells (PEMFCs) are considered to be technologically the advanced systems inclining with their ability to support a wide range of capacity requirements. Technical classification of PEMFCs predominantly falls under two branches, viz., low-temperature PEMFC (LT-PEMFC) which operates in the temperature range of 60-80°C, and the high-temperature PEMFC (HT-PEMFC), which works in the range of 150-180°C. The need for an electrocatalyst to improve the kinetics of the relevant reactions i.e., hydrogen oxidation reaction (HOR) at the anode, and oxygen reduction reaction (ORR) at the cathode, in PEMFCs has opened a wider door for scientific and industrial exploration in this field.

[0006] The commercial PEMFCs are dominatingly dependent on platinum (Pt) supported carbon (C) catalysts or their alloys (refer, Wu, J. and Yang, H., Acc. Chem. Res. 2013, 46 (8), pages 1848-1857). The major challenges faced by the state-of-the-art catalysts as an outcome of the prevailing acidic environment and voltage fluctuations owing to start-stop cycles trigger carbon corrosion further in association with an enhancement of Pt dissolution, and particle agglomeration, leading to an augmented reduction in the electrochemical surface area (ECSA) of the catalyst. Apart from these material- specific limitations, the PEMFCs also suffer from the obstructions imposed by the processes involved during the utilization of the electrocatalyst to PEMFC operational cells or stacks. One of the most known limitations is the oxygen starvation faced by the cathode at a typical operating potential range under H2-air feed conditions. When PEMFCs are operated in air instead of pure oxygen at the cathode, the declination in oxygen partial pressure is observed as a payoff of diminished concentration of oxygen in air along with the presence of water (the byproduct of the ORR) and the formation of “nitrogen blanket” as an outcome of the accumulation of non-reactive gases over cathode catalyst layer.

[0007] The presence of the ionomer binder (usually Nafion® - sulfonated tetrafluoroethylene -based fluoropolymer-copolymer) as an essential ingredient in the electrode to establish an active “triple-phase boundary”, further reduces the oxygen diffusion to the reactive sites. In comparison with that of low temperature (LT)-PEMFC, and high temperature (HT)-PEMFC has liquid phosphoric acid (H3PO4) in the electrode, apart from the ionomer binder. This further reduces the oxygen solubility in the electrode interface along with its another major drawback of an increased rate of catalyst corrosion. An increased steam partial pressure and the acidic pH range by H3PO4 in HT-PEMFC offers a fertile environment that can accelerate carbon corrosion, considering the long-term performance and return on investment (ROI) from the commercial deployments of PEMFCs, an inflated need for addressing support corrosion and oxygen starvation issues is in a high demand.

[0008] Hence, in a nutshell, there are different PEMFC reported in the literature, with different catalysts however they suffer from disadvantages or limitations such as: i) sluggishness due to oxygen harvesting and self-humidification at cathode side in the cell, hence, less oxygen is available for ORR thus decreasing performance and stability; ii) carbon corrosion; iii) water content is higher; iv) dense material over the time of testing of cell, etc.

[0009] Thus, there is a need in the art to provide a new electrocatalyst for cathode or anode or both in PEMFCs, which are more corrosion-resistant and have dedicated interfaces for oxygen enrichment assisting the utilization of metal in a better way during ORR.

[0010] OBJECTIVES OF THE INVENTION

[0011] An object of the present invention is to provide an electrocatalyst for a proton exchange membrane fuel cell (PEMFC) to enhance the oxygen reduction reaction (ORR).

[0012] Another objective of the present invention is to provide a process of preparation of an electrocatalyst.Yet another objective of the present disclosure is to provide a half proton exchange membrane fuel cell comprising the electrocatalyst.

[0013] Still another objective of the present disclosure is to provide a full proton exchange membrane fuel cell comprising the electrocatalyst.

[0014] SUMMARY OF THE INVENTION

[0015] In an aspect, the present invention relates to an electrocatalyst for oxygen reduction reaction (ORR) comprising,

[0016] (i) at least one metal Ml selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof.

[0017] (ii) at least one metal oxide M2 selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof.

[0018] (iii) A catalyst support selected from silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃), or any combination thereof;

[0019] wherein the metal Ml is anchored onto the catalyst support coated with metal oxide M2.

[0020] In an embodiment the electrocatalyst the weight % of metal Ml is in the range of 45-55% based on weight% of the support, preferably in the range of 47% or 50% based on weight % of the support and the weight % of the metal oxide M2 is in the range of 10-40 % based on the weight % of the support.

[0021] In another embodiment the electrocatalyst comprises metal Ml with particle size of metal Ml in the range of 3-5 nm and metal oxide M2 coated, with particle size in the range of 5-10 nm.

[0022] In an embodiment, the electrocatalyst for oxygen reduction reaction (ORR) comprises platinum metal nanoparticles anchored to a catalyst support coated with cerium oxide nanoparticles wherein the catalyst support is spherical particles of silicon dioxide indicated as Pt / SiO2@CeO2. In a particular embodiment, the electrocatalyst comprises cerium oxidesuch that its weight is 10%, 30% or 40% based on the weight of the catalyst support silicon dioxide.

[0023] In another embodiment the electrocatalyst is crystalline having oxygen vacancy defects. In yet another embodiment the electrocatalyst is carbon free.

[0024] In another aspect the present invention further relates to a process for preparing an electrocatalyst for an oxygen reduction reaction (ORR) comprising the steps of:

[0025] a) preparing a catalyst support material comprising spherical particles of a support selected from silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃), or any combination thereof;

[0026] b) coating a metal oxide M2 onto the support of step a) by ethylene glycol assisted method wherein the metal oxide M2 is selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;

[0027] c) loading a metal Ml onto the M2-metal oxide coated onto the support by polyol-assisted reduction method to obtain the electrocatalyst wherein the metal Ml is selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof.

[0028] In an embodiment, the process of loading the metal Ml onto the metal oxide M2 coated support proceeds through the polyol assisted reduction method wherein metal Ml precursor is dissolved in a reducing agent and is selected from a salt, acid, halide, haloacid, acetyl acetonate salt or any combination thereof and the reducing agent is selected from urea, sodium hydroxide (NaOH), potassium hydroxide (KOH), and hydrogen peroxide (H2O2) or any combination thereof.

[0029] In an aspect, the electrocatalyst of the present invention relates to an electrocatalyst for oxygen reduction reaction (ORR) in a Proton Exchange Membrane Fuel Cell (PEMFC).

[0030] In another aspect, the present invention relates a half-fuel cell comprising:

[0031] i. said electrocatalyst,ii. working electrode,

[0032] iii. reference electrode,

[0033] iv. counter electrode,

[0034] v. power supply, and

[0035] vi. electrolyte solution;

[0036] wherein said electrocatalyst is coated or decorated onto said working electrode.

[0037] In another aspect, the present invention provides a full fuel cell comprising:

[0038] i. an anode,

[0039] ii. a cathode,

[0040] iii. proton exchange membrane,

[0041] iv. said electrocatalyst, and

[0042] v. gas diffusion layer;

[0043] wherein said electrocatalyst is coated or deposited onto said gas diffusion layer.

[0044] BRIEF DESCRIPTION OF THE DRAWING

[0045] FIG. 1 illustrates schematic representation of the synthesis of the Pt / SiO2@CeO2 electrocatalyst and demonstration of PEMFC employing the catalyst as the cathode.

[0046] FIG. 2 shows (a) FESEM image of SiO₂; The TEM and HRTEM images of (b) SiO₂, (c) 10Wt%SiO₂@CeO₂, (d and e) SiO₂@CeO₂-30% and SiO₂@CeO₂-40%; (f and g) Scanning Tunneling Microscopy (STM) image corresponding elemental mapping of SiO₂@CeO₂-30Wt%, and (h) TEM image of Pt / SiO₂.

[0047] FIG. 3 shows TEM image of (a) SiO₂@CeO₂ -30Wt%,; the HRTEM images of (b, c) SiO₂@CeO₂-30Wt%,; (d) line profiling of SiO₂@CeO₂-30Wt%, showing corresponding d-spacing obtained; the HRTEM images of (e, f) Pt / SiO₂@CeO₂-30Wt%,; (g, h) Pt / SiO₂;

[0048] (i) line profiling showing corresponding d-spacing of Pt / SiO₂; (j) the particle size distribution of Pt in Pt / SiO₂@CeO₂ -30Wt%,, and (k) STEM image and corresponding elemental mapping of Pt / SiO₂@CeO₂-30Wt%, showing uniform distribution of the individual elements.FIG. 4 shows (a) FESEM image, and (b) elemental mapping of Pt / SiO2@CeO2-30% material.

[0049] FIG. 5 shows XRD spectra of (a) SiO₂ and various CeO₂ coated SiO₂ samples, and (b, c) Pt / C, Pt / SiO₂@CeO₂, and Pt / SiO₂; (d, e) the comparative Raman spectra of SiO₂ and various CeO₂ coated SiO₂ samples; and (f) the comparative EPR spectra of SiO₂, SiO₂@CeO₂-30%, and Pt / SiO₂@CeO₂-30%.

[0050] FIG. 6 shows the comparative (a) CV, (b) LSV, and (c) Tafel plots corresponding to ORR in 0.1 M HCIO4 electrolyte of all the catalysts; (d) the mass activity and specific activity measured at 0.85 V of all the catalysts; (e) the comparative CV profiles of reductive oxygen stripping of Pt / SiO2@CeO2-30% and Pt / C with different potential varying from 0.6 to 1.5 V vs. RHE; (f) the plot of charge of oxygen adsorption normalized with ECSA vs. varying potential suggesting the oxygen enrichment during ORR; (g) the comparison of the LSV profiles of Pt / SiO2@CeO2-30% performed before and after the AST analysis; (h) the plot of charge of oxygen adsorption normalized with ECSA before and after AST; and (i) the bar diagram depicting the mass activity before after AST analysis.

[0051] FIG. 7 shows the contact angles analysis of (a) Pt / SiO2@CeO2-30% catalyst, and (b) Pt / C catalyst.

[0052] FIG. 8 shows comparative I-V polarization plots recorded during the single cell evaluation of the MEA with the Pt / SiO2@CeO2-30% and Pt / C in (a) H2-O2; (b) H2-Air feed; (c) the plot depicting the potential difference in H2-O2 and H2-Air with current density; and (d) the bar diagram showing the current density at 0.6 V in H2-O2 and H2-Air for both MEAs.

[0053] FIG. 9 shows the comparitive solid-state CV profiles before and after the AST cyclets of (a) Pt / SiO₂@CeO₂-30%, and (b) Pt / C based MEAs.

[0054] FIG. 10 shows the representative drawing of (a) half fuel cell; and (b) full fuel cell.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] The PEMFC proceeds with Oxygen Reduction Reaction at the cathode. The ORR (Oxygen Reduction Reaction) is enhanced by catalysts accelerating the reaction rate and improving efficiency and selectivity, primarily by lowering the reaction's activation energy barrier.This is especially crucial for the PEMFC, where the ORR is the kinetically sluggish step that limits overall performance.

[0057] In an aspect, the present invention provides an electrocatalyst for oxygen reduction reaction (ORR) comprising,

[0058] (i) at least one metal Ml selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof.

[0059] (ii) at least one metal oxide M2 selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and Ytterbium (Yb) or any combination thereof.

[0060] (iii) catalyst support selected from silicon dioxide (SiC ), zirconium oxide (ZrOi), titanium oxide (TiCh), and aluminum oxide (AI2O3), or any combination thereof;

[0061] wherein the metal Ml is anchored onto the catalyst support coated with metal oxide M2.

[0062] The electrocatalyst comprises Ml as an active catalyst selected from a group comprising nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof. In an embodiment Ml is platinum. Preferably Ml are nanoparticles with particle size in the range of 3-5 nm. In another embodiment, the oxidation state of the Ml-metal is in the range of 0 to 4+. The metal Ml is anchored onto the support which is coated or decorated with metal oxide M2.

[0063] The term “anchoring” used herein refers to binding of the molecule or metal with the surface of the support or at any site of the support. It also refers to a location where a chemical group / metal attaches to a surface or molecule. In an embodiment, the Ml-metal particles are uniformly or partially dispersed over the M2-metal oxide decorated or coated support.

[0064] In another embodiment, the electrocatalyst comprises a catalyst structure wherein metal nanoparticles Ml, are decorated over metal oxide M2 coated support, and utilizes the electronic interaction between the support and the metal(s), which enables the establishment of the dominant 0 oxidation state of Ml-metal when compared to with thatof the oxidized phases (e.g. 2+, 4+, etc.). The Ml metal particles are dispersed in the form of interconnected networks, with the M2-metal oxide decorated or coated support. This interconnected Ml -metal particles network demonstrates improved durability by reducing susceptibility to migration, dissolution, and agglomeration, further supporting the objective of forming a continuous network of Ml -metal particles.

[0065] In an embodiment, the Ml metal are nanoparticles having particle size in the range of 3-5 nm. In another embodiment, the weight % of Ml-metal is in the range of 45%-55% based on the weight of the support. Preferably it is 47% or 50% based on weight of the catalyst support.

[0066] The electrocatalyst comprises at least one M2-metal oxide which is decorated over the support such that it intimately binds with the active catalyst Ml which is anchored onto the support. The M2-metal oxide is selected from but not limited to oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof.

[0067] The metal oxide M2 is coated or decorated onto the catalyst support to enhance the electrocatalytic activity of the active catalyst. Metal oxide creates oxygen vacancy defects (VO) which are essentially missing oxygen atoms in a crystal lattice, common in metal oxides, creating dangling bonds and trapped electrons that drastically alter properties like conductivity, light absorption, and catalytic activity, making them crucial for its applications. These defects form at high temperatures or low oxygen, act as positively charged carriers (releasing electrons), and are vital for electrocatalytic activity of metal catalysts, photocatalysis and gas sensing.

[0068] In an embodiment, the electrocatalyst comprises defective M2-metal (e.g. Ce3+in case of cerium) known to act as an oxygen reservoir, which further acts as a seed for implementing a better ORR kinetics in regard of electrically inert metal oxide systems. It is observed that ceria can neatly transform between the Ce3+ and Ce4+ oxidation states, which is conducive to gain and loss of electrons, thus facilitating the electrochemical reaction. Secondly, due to the ability of CeO2 to switch between Ce3+ and Ce4+ states, with their concentration and distribution controlled by doping, size, and morphology, enhancing catalytic activity itP_W0100795

[0069] contains many oxygen vacancies within its structure, which is beneficial for improving oxygen mobility. Thus, oxygen vacancies in ceria CeO₂ are missing oxygen atoms, creating defects crucial for its high oxygen storage capacity (OSC) and redox properties, vital for catalysis for ORR. In an embodiment, the electrocatalyst of the present invention has increased oxygen vacancies (VO) defects by at least 20% than any electrocatalyst having a support without the metal oxide M2 coating.

[0070] In an embodiment, the particle size of metal oxide M2 nanoparticles is in the range of 5-10 nm. In another embodiment, the oxidation state of the M2-metal in the metal oxide M2 is in the range of 2+ to 4+. In yet another embodiment, the weight % of the metal oxide M2 in the electrocatalyst is in the range of 10-40 % based on the weight of the support.

[0071] Catalyst supports provide a stable surface area that disperses active catalyst metals to maximize reaction sites. They boost efficiency by preventing clumping and enabling better reactions. The support for the present invention is selected from but not limited to silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃), or any combination thereof. Preferably the electrocatalyst support in the present invention is carbon-free.

[0072] In an embodiment the support is silicon dioxide. SiCh is known for its water-retention properties making it an ideal carbon-free, corrosion-resistant substrate for supporting the Pt-nano CcCh interface. In an embodiment the SiO₂ silica particles are in spherical shape and having smooth topological characteristics with a diameter in a range of 400 nm - 450 nm.

[0073] The electrocatalyst of the present invention comprises the M2-metal oxide nanoparticles in such a manner wherein it is decorated on the surface of the catalyst support in the form of a layer. The decorated or coated M2-metal oxide onto the support provides an active interface for establishing improved metal support interaction between the Ml nanoparticle, and coated M2-metal oxide onto the support. Further the Ml -metal is anchored with the support via M2-metal oxide. In an embodiment, the M2-metal oxide forms a layer over the surface of the support or over the edges of the support. In another embodiment, the metal oxide M2 is completely deposited over the surface of the support, making it preferably aP_W0100795

[0074] thin film / layer. This thin layer of metal oxide M2 over the catalyst support enhances oxygen storage properties due to its intrinsic characteristics.

[0075] In an embodiment, the weight % of M2-metal oxide is in the range of 25-35% based on weight % of the support. In specific embodiment, the weight % of M2 -metal oxide is 10% based on weight % of the support, 30% based on weight % of the support or 40% based on weight % of the support.

[0076] In an embodiment, the electrocatalyst is crystalline in nature, where the support is converted from amorphous to crystalline by the presence of crystalline M2-metal oxide and Ml metal. In yet another embodiment, the electrocatalyst of the present invention comprises defective M2-metal known to act as an oxygen reservoir, which further enables better ORR kinetics in electrically inert metal oxide systems. Preferably M2 metal is Ce3+.

[0077] In an embodiment the electrocatalyst of the present invention is Pt / SiO2@CeO2 wherein platinum metal nanoparticles are anchored onto a catalyst support of silicon dioxide which is coated or decorated with cerium oxide.

[0078] In a particular embodiment, the electrocatalyst of the present invention is carbon- free. Carbon free support acts as a corrosion resistant substrate for electrocatalyst while usual carbon based substrates suffer from support corrosion in acidic ORR kinetics

[0079] In an embodiment, the electrocatalyst is nearly non porous with minimal porosity. Being minimally porous is advantageous as the exposure of Pt nanoparticles will be better in comparison with that of the porous electrocatalyst, as the Pt nanoparticles in porous substrates may block the pores of the support due to which the access to the reactant gases will be reduced.

[0080] In an embodiment, the M2-metal oxide coated onto the support has a rough surface property.

[0081] In another aspect, the present invention provides a process of preparing the electrocatalyst of the present invention, comprises steps of:a) preparing a catalyst support material comprising spherical particles of a support selected from silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃), or any combination thereof;

[0082] b) coating a metal oxide M2 onto the support of step a) by ethylene glycol assisted method wherein the metal oxide M2 is selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;

[0083] c) loading a metal Ml onto the M2-metal oxide coated onto the support by polyol- assisted reduction method to obtain the electrocatalyst wherein the metal Ml is selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof.

[0084] In an embodiment the polyol assisted reduction method in the process of preparing comprises dissolving a metal Ml precursor in a reducing agent wherein the Ml precursor is selected from a salt, acid, halide, haloacid, acetyl acetonate salt or any combination thereof and the reducing agent is selected from urea, sodium hydroxide (NaOH), potassium hydroxide (KOH), and hydrogen peroxide (H2O2) or any combination thereof.

[0085] In an embodiment, the metal oxide M2 is coated or decorated onto the support of step a) by ethylene glycol assisted method, comprising the steps of:

[0086] (i) mixing and sonicating the support material of step a) in ethylene glycol to obtain a dispersion;

[0087] (ii) adding and mixing 10-40 wt. % of M2-metal oxide precursor or salt in the dispersion of sub-step i) under sonication at temperature in the range of 25-35 °C for time period in the range of 10-20 minutes to obtain a 1stmixture;

[0088] (iii) refluxing the 1stmixture of sub- step ii) at temperature in the range of 120 to 140 °C for time period in the range of 14-16 h followed to obtain a wet cake of M2-metal oxide coated onto the support; andP_W0100795

[0089] (iv) centrifuging, washing and drying the wet cake of sub-step iii) to obtain M2-metal oxide coated onto the support.

[0090] In a further embodiment, the anchoring of metal Ml onto the M2-metal oxide coated onto the support proceeds by the polyol-assisted reduction method, comprising the steps of:

[0091] (i) mixing and sonicating the M2-metal oxide coated onto the support material with a reducing agent in a solvent at temperature in the range of 25-35 °C for time period in the range of 10-20 minutes to obtain a 2ndmixture;

[0092] (ii) adding and mixing Ml-metal precursor or salt in the 2ndmixture of sub-step 1) under sonication at temperature in the range of 25-35 °C for time period in the range of 45 to 90 minutes to obtain a 2ndmixture;

[0093] (iii) stirring the 2ndmixture for time period in the range of 7-11 h followed by heating at temperature in the range of 80-100 °C for time period in the range of 45-90 minutes to obtain a 3rdmixture;

[0094] (iv) adding ethylene glycol in the 3rdmixture followed by stirring at temperature in the range of 25-35 °C for time period in the range of 7-11 h to obtain a 4thmixture;

[0095] (v) heating the 4thmixture at temperature in the range of 110-130 °C for time period in the range of 5-7 h to obtain crude electrocatalyst in the form of wet cake; and

[0096] (vi) filtering, washing and drying the wet cake of crude electrocatalyst of sub-step 5) to obtain the electrocatalyst.

[0097] In another embodiment, the sonication of sub- step i) of step b) is done at temperature in the range of 25-35 °C for time period in the range of 45-80 minutes.

[0098] In an embodiment, the centrifugation of sub-step iv) of step b) is done in Thermofisher machine at speed in the range of 9000-11000 rpm.

[0099] In an embodiment, the washing of sub-step iv) of step b) is done using a C1-C4 alcoholic solvent selected from methanol, ethanol, propanol, and so on.In an embodiment, the drying of sub-step iv) of step b) is done in two stages where in 1ststage, it is done at temperature in the range of 60-80 °C for time period in the range of 8-10 h, and in 2ndstage, it is done at temperature in the range of 380-420 °C for time period in the range of 2-4 h.

[0100] In another embodiment, the metal oxide M2 precursor is based on salt or precursor selected from nitrate, acetate, carbonate and sulphate. E.g. M2-metal nitrate, M2-metal acetate, M2-metal carbonate, M2-metal sulphate etc.

[0101] The polyol-assisted reduction produces metal and metal oxide nanoparticles (NPs) with controlled size, shape, and crystallinity. In an embodiment the polyol is a high-boiling-point alcohol like ethylene glycol (EG) or diethylene glycol (DEG), functioning as both the solvent and the reducing agent.

[0102] In an embodiment, the reducing agent is selected from but not limited to urea, sodium hydroxide (NaOH), potassium hydroxide (KOH), and hydrogen peroxide (H2O2) or any combination thereof.

[0103] In another embodiment, the Ml -metal precursor is based on salt or precursor selected from acid, halide, haloacid, and acetyl acetonate salt or any combination thereof. Preferably the metal precursor is halo acid.

[0104] In an embodiment, the washing of sub-step vi) of step c) is done using a mixture of solvents selected from C1-C4 alcoholic solvent and water, wherein the C1-C4 alcoholic solvent is selected from methanol, ethanol, propanol, and so on.

[0105] In an embodiment, the drying of sub-step vi) of step c) is done at temperature in the range of 100-120 °C for time period in the range of 8-10 h.

[0106] In an embodiment, the support material comprising spherical particles is prepared by:

[0107] a) mixing an alcoholic solvent, aqueous solvent and base followed by stirring at temperature in the range of 25-35 C for time period in the range of 25-40 minutes to obtain a solution;b) adding and stirring a support precursor in the solution of step a) at temperature in the range of 25-35 C for time period in the range of 22 to 26 h to obtain crude support material; and

[0108] c) centrifuging, washing and drying the crude support material to obtain the support material.

[0109] In another embodiment, the alcoholic solvent of step a) is selected from but not limited to methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutanol, tertiary butanol, and so on.

[0110] In another embodiment, the aqueous solvent is water or DI water.

[0111] In another embodiment, the base is selected from but not limited to ammonia and ethanol amine or any combination thereof.

[0112] In another embodiment, the support precursor is selected from but not limited to tetraethyl orthosilicate (TEOS), Tetramethyl orthosilicate (TMOS), dimethyl (diethoxy) silane (DMDES), methyl(triethoxy)silane (MTES), ethyl(triethoxy) silane (ETES), propyl(triethoxy) silane (PTES), and pre -hydrolysed ethyl silicate or any combination thereof.

[0113] In an embodiment, the washing of step c) is done at least two times, using a solvent selected from C1-C4 alcoholic solvent, wherein the C1-C4 alcoholic solvent is selected from methanol, ethanol, propanol, and so on.

[0114] In an embodiment, the drying of step c) is done at temperature in the range of 60-80 °C for time period in the range of 7-9 h.

[0115] In an aspect, the electrocatalyst of the present invention relates to an electrocatalyst for oxygen reduction reaction (ORR) in a Proton Exchange Membrane Fuel Cell (PEMFC).

[0116] In another aspect, the present invention relates to a half-fuel cell comprising:

[0117] i. said electrocatalyst,

[0118] ii. working electrode,

[0119] iii. reference electrode,iv. counter electrode,

[0120] v. power supply, and

[0121] vi. electrolyte solution;

[0122] wherein said electrocatalyst is coated or decorated onto said working electrode.

[0123] In another embodiment, the half fuel cell is half proton exchange membrane fuel cell.

[0124] In another embodiment, the working electrode is selected from but not limited to glassy carbon electrode, carbon paper, carbon cloth, nickel foam and so on.

[0125] In another embodiment, the reference electrode is selected from but not limited to Ag / AgCl electrode, mercury-mercury oxide (Hg / HgO), mercury-mercury(I) sulfate (Hg / HgiSC ), calomel electrode and so on.

[0126] In another embodiment, the counter electrode is selected from but not limited to graphite carbon rod, platinum mesh, platinum wire and so on.

[0127] In another embodiment, the half-fuel cell containing said electrocatalyst shows 1.8 times higher mass activity and 4.4 times higher specific activity than the half fuel cell containing Pt / C (without electrocatalyst).

[0128] In a particular embodiment the electrocatalyst is Pt / SiO2@CeO2-30% which shows significantly enhanced activity in terms of Eo, E1 / 2, mass activity and specific activity.

[0129] In another aspect, the present invention provides a full fuel cell comprising:

[0130] i. an anode,

[0131] ii. a cathode,

[0132] iii. proton exchange membrane,

[0133] iv. said electrocatalyst, and

[0134] v. gas diffusion layer;

[0135] wherein said electrocatalyst is coated or deposited onto said gas diffusion layer.In another embodiment, the gas diffusion layer is placed between the anode and the proton exchange membrane. In another embodiment, the gas diffusion layer is placed between the cathode and the proton exchange membrane.

[0136] In another embodiment, the proton exchange membrane is selected from but not limited to perfluorosulfonic acid (PFSA) membrane (Nafion), expanded polytetrafluoroethylene (ePTFE) or expanded polyethylene (ePE) breathable membrane (GORE TEX), and sulfo-phenylated polyphenylene -based cation exchange membrane (Pemion).

[0137] In another embodiment, the anode is selected from but not limited to platinum dispersed over carbon support, Pt / C, Pd / C, and ruthenium based catalysts over support. In another embodiment, the cathode is selected from but not limited to platinum dispersed over carbon support and Pd / C.

[0138] In another embodiment, the gas diffusion layer(s) is / are made of nonwoven carbon paper gas diffusion medium with total thickness of 285 pm (microns) (GDL 36 BB), 39 CC gas diffusion layer (GDL) [it is a component of a proton exchange membrane fuel cell (PEMFC) that is made of carbon paper and has a microporous layer (MPL)], non-woven carbon paper with a Microporous Layer (MPL) that has been PTFE treated to 5 wt%, and has a total thickness of 325 pm (microns) [GDL 38 BC).

[0139] EXAMPLES

[0140] Following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

[0141] Materials Required: Tetraethyl orthosilicate (TEOS), chloroplatinic acid (HiPtCk,. 6H2O), and cerium nitrate hexahydrate [Ce(NO3)3. 6H2O] were procured from Sigma Aldrich. Ethylene glycol, ammonia (30%), urea, isopropyl alcohol, and perchloric acid were procured from Thomas Baker. All chemicals were analytical grade and were utilized as procured.

[0142] Example 1: Preparation of Pt / SiO2@CeC>2 electrocatalyst:

[0143] Step A: Preparation of Silica (SiCh) material:In a synthesis of silica (SiC ) spheres, 80 ml of isopropyl alcohol, 16 ml of DI water, and 4 ml of 30% aqueous ammonia were added and the mixture was stirred in a conical flask for 30 min. Subsequently, 2 ml of TEOS was added and the stirring was continued at room temperature (30 °C) for another 24 h. The formed SiOi nanospheres at this stage were collected via centrifugation and washed twice with ethanol. The product was collected after drying at 70 °C for 8 h.

[0144] Step B: Preparation of SiO2@CeC>2 material:

[0145] Typically, for synthesizing the ceria-coated silica spheres (SiO2@CeO2) an ethylene glycol assisted protocol was followed. About 300 mg of the SiC was dispersed in 43 ml of ethylene glycol and the mixture was kept under sonication for an hour. Following this, 2.25 ml of Ce (NO3)3.6H2O solution with varied concentration (weight percentage calculated with respect to the weight of SiC ) was added to obtain SiO2@CeO2-10%, SiO2@CeO2-30%and SiO2@CeO2-40%. This was under sonication which was continued for another 15 min. The mixture was subsequently refluxed at 130 °C for 15 h. After cooling, the product was collected via centrifugation and washed with ethanol. The wet cake was then dried overnight at 70 °C and thereafter at 400 °C for 3 h to obtain SiO2@CeO2. To further understand the effect of CcCh concentration, synthesis was carried out by varying the amount of respective precursors.

[0146] Step C: Preparation of Pt / SiO2@CeC>2 catalyst:

[0147] The experiments were set for the theoretical loading of 50 Wt.% of Pt on SiO2@CeO2 via a polyol-assisted reduction protocol. Uniform deposition of reduced platinum (Pt) nanoparticles over silica- supported ceria was employed using urea-assisted “Homogenous Deposition” (HD) protocol. For this, 400 mg of urea and 30 mg of SiO2@CeO2 were added to 60 ml of DI water followed by this, the mixture was sonicated for 15 min. 400 microliters of 0.5 M H2PtC16.6H2O was added and the mixture was further sonicated for 1 h. The obtained solution was then stirred overnight, heated up to 90 °C, and maintained at the temperature for an hour. When the reaction mixture was cooled down to room temperature, 60 ml of ethylene glycol was added, and the mixture was kept for overnight stirring. The decoration / anchoring of the Pt nanoparticles on SiO2@CeO2 (Pt / SiO2@CeO2) was achieved by heating the reaction mixture to 120 °C for 6 h. After cooling down, the obtainedPt / SiO2@CeO2 was collected via filtration followed by washing with ethanol-water mixture, and the obtained wet cake was dried overnight at 110 °C.

[0148] The SiO2 spheres (as prepared in step a) are the substrate for the CeC decoration. This process utilizes -OH surface functionality, ensuring a well-controlled and uniform decoration of the CeO2 nanoparticles. The decorated CeO2 nanoparticles thus provide an active interface for establishing improved metal support interaction between the Pt nanoparticles and SiO2@CeO2 support. Established anchoring of Pt nanoparticles over SiO2@CeO2 surface is availed by a polyol assisted reduction protocol. The exclusive capability of SiCh with in terms of the water management explains the need for this species in the support system. Enhanced availability of the defective ceria (Ce3+) is known to act as an oxygen reservoir, which further acts as a seed for implementing a better ORR kinetics in regard of electrically inert metal oxide systems. Decoration of Pt nanoparticles over SiO2@CeO2 ensures and utilizes an electronic interaction from the support to metal, which is further portrayed as a scientific route for the establishment of the dominant Pt° state when compared to with that of the oxidized phases (Pt2+and Pt4+).

[0149] To understand the optimum growth of CcCh particles aiming at best possible composition, different concentrations of the precursor solutions were aided with aiming at the availability of lOWt %, 30Wt% and 40Wt% Ce with respect to the aided weight of SiC and the obtained products were named as SiO2@CeO2 - 10%, SiO2@CeO2 - 30% and 40%SiO2@CeO2- 40% respectively.

[0150] Example 2: Physical characterization

[0151] Micro structure analysis of the catalysts was carried out with the aid of FEI Nova Nano SEM 450 field emission scanning electron microscope (FESEM). FIG. 2a depicts the FESEM (Field emission scanning electron microscope) image of uniformly sized SiCh spheres having smooth topological characteristics with a diameter of in a range of 400 nm - 450 nm. Observations figured out from the FESEM analysis and corresponding elemental mapping in FIG. 4a and 4b corroborates with the uniformity in the dispersion and Pt nanoparticles which aligns with the peculiarities observed from TEM images of Pt / SiO2@CeO2-30% in FIG. 3 (a-k).Powder samples were directly mounted on a carbon tape. Insight understanding of high-resolution nano images was accomplished by FEI TECNAI G2 F20 transmission electron microscope (TEM). JEOL JEM F-200 equipment was advocated for the high-resolution TEM analysis. Followed by the dispersion of samples in ethanol, the sample suspensions were coated over a 200-micron carbon-coated copper mesh and dried overnight prior to the TEM and HRTEM analyses. Correlative aspects with respect to the TEM (Transmission electron microscopy) of SiCh spheres is observed in FIG. 2b. The decoration of CeCh nanoparticles over these SiCh spheres is depicted in FIG. 2c-2h with varied concentration of Ce based precursor. Impact of an increased concentration over the formation of this nano CeOi layer can be correlated from the same. As inferred from FIG. 2c, 10 Wt.% of CeCh decorated SiCh spheres shows an incomplete coverage by CeOi nanoparticles. Depicted TEM images confirm highly exposed surface of SiC with relatively decreased amount of CeOi particle coverage. An increment in the coverage owing to an appropriate formation of a thin nanoceria layer is obtained by the decoration of 30 Wt.% CcC over SiCh spheres (FIG. 2d-2g). Formation of a continuous layer of CeC over the SiCh spheres is achieved as depicted in FIG. 2d by establishing 30Wt.% decoration. A better understanding of the interconnected layer of CeCh is evident in FIG.2e. Elemental distribution of the individual components confirms the uniformity of the same (FIG. 2f and FIG. 2g). The thin layer of nano-CeO2 enhances oxygen storage properties due to its intrinsic characteristics. The corresponding high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) (FIG. 2f) image of 30%SiO2@CeO2 clearly depicts an enhanced roughness over the SiC spheres lining up with the decoration of CcC particles aligning with the conclusions obtained from the prior TEM analysis (FIG. 2d). A more critical overview with respect to the elemental composition of the individual support spheres shows a uniform distribution of the corresponding elements viz, Si, Ce, and O (FIG. 2g).

[0152] Conclusive pieces of evidence concerning thin nanoceria layer coating are further correlated with the corresponding overlay mapping which shows a thin layer of Ce over the edges of SiCh spheres which confirms the inferences turned out from the initial TEM analysis. It has been observed that further increase in the percentage of CeCh initiates the transformation to a bulk nature as inferred from FIG. 2h which is observed as an outcome of 40Wt% CeO2 decoration over SiC spheres.Insight into the crystal structure of the prepared materials was obtained via powder X-ray diffraction analysis (PXRD), performed in a Rigaku Smart Lab diffractometer with Cu Ka radiation (k = 1.5406 A) in the 29 range of 10 to 90° with a scan rate of 5 min-1. The SiO2@CeO2-30% was employed as the substrate for housing Pt nanoparticles. The coverage of the CeC particles over the SiCh spheres is vividly visible from the TEM images as evidenced in FIG. 3a, which in turn is backed by the HRTEM FIG. 3b and 3c images with a corresponding d-spacing value of 0.31 nm coexisting with the fluorite structure of CcCh (FIG. 3b). Obtained line profiling (FIG. 3d) lining up with the depicted d spacing values concludes a clear and coherent appearance of the measured lattice spacing. Effective anchoring and coverage of platinum nanoparticles over SiO2@CeO2-30% are observed from the TEM images of Pt / SiO2@CeO2-30% (FIG. 3e, and 3f). The interconnected network of platinum nanoparticles is attained intentionally owing to minimize the inferior electrical conductivity of the oxide support and as an attempt to enhance the oxygen spill over. As observed in FIG. 3f, the complete coverage of the support spheres using platinum nanoparticles enhances conductivity by partially mitigating the electrical inertness of the SiCh support. This approach aligns with the intended design of fully coating the support spheres with platinum to improve conductivity. Additionally, the interconnected Pt nanoparticle network demonstrates improved durability by reducing susceptibility to migration, dissolution, and agglomeration, further supporting the objective of forming a continuous network of Pt nanoparticles. Confirmation on lattice parameters and exposed planes of platinum nanoparticles has been obtained from the HRTEM analysis and the corresponding d-spacing values of the same. FIG.3g and 3h confirms the presence of crystalline particles over the amorphous support. Obtained d-spacing value of 0.227 nm concludes the exposure of (111) plane of platinum. This is further supported by the obtained line profiling features (FIG. 3i) of the lattice depicted in FIG. 3h. Information regarding the particle size of the anchored platinum nanoparticles is observed in the FIG. 3j. As depicted, the average particle size of platinum nanoparticle aligns around 3 nm. Conclusive aspects in regard of the uniformity in the elemental distribution are summarized in the FIG.

[0153] 3k. Observed evenness of all the individual elements viz; Si, Ce, O and Pt can be figured out from the attained elemental mapping. An evident contribution of Ce towards proper anchoring of Pt can be concluded from FIG. 3k. The dense interconnected layer of platinum is formed in the edges of SiO2@CeO2-30% spheres which is more vivid from the depicted overlay image, were the concentration of Ce is prominent as per the elementalmapping observed from FIG. 3k. The effective role of CeO2as an anchoring site of Pt is further pronounced in a furnished manner via the topological comparison of platinum decorated SiO2spheres (Pt / SiO2). Incomplete coverage of Pt leading to specific agglomerated areas over the SiO2spheres which is further supported by the observations dug out from X-ray diffraction (XRD) analysis of the same. Correlative inferences in regard of the contribution of Ce as an anchoring site for Pt can be added up to this by inferring to the comparative mapping pattern of Ce and Pt, which is further appreciating the inferiority in the anchoring aspects as discussed in regard of Pt / SiO2.

[0154] The XRD analysis confirmed crystallographic properties and the purity of the synthesized materials. FIG. 5a depicts the XRD patterns, showing the evolution of ceria coated SiO2spheres. As observed, a vivid transformation of amorphous silica to a crystalline further confirms the effective anchoring of CeO2nanoparticles. A surge in crystallinity is evident as the concentration of the decorated CeCh nanoparticles increases from 10% to 40%. A broad peak at a 29 value of 25° portrays the amorphous nature of silica, which gradually diminishes as CeO2coverage intensifies further, leading to a notable decrement in the relative intensity of this peak as CeCh concentration rises from 10% to 40%. The distinct peaks associated with CeCh crystallographic structure (JCPDS: No 00-034-0394), corresponding to a cubic fluorite phase with the space group of Fm3m. In the sample with 10 Wt% CeO2on SiO2, limited exposure of CeO2planes is attributed to incomplete coverage of CeO2nanoparticles on the SiO2spheres, as confirmed by TEM images in FIG.

[0155] 2b.

[0156] The prominent planes corresponding to CeO2and their exposure increases along with the surge in the coverage of CeO2nanoparticles over SiO2spheres, with a simultaneous decrease in the intensity of the amorphous phase contributed by SiO2(broad peak observed at 25°). The exposure of all the prominent planes associated with CeO2is observed in FIG.

[0157] 5a, specifically (111), (200), (220), (311), (400), (331), (420), and (422) planes at 29 angles of 28.5°, 33.1°, 47.5°, 56.3°, 59.1°, 69.4°, 76.7°, and 88.4°, respectively. The incorporation of Pt nanoparticles over the synthesized support was further analyzed based on the crystallographic domains. The observed XRD patterns (FIG. 5b) shows a high similarity index with that of the state-of-the-art catalyst (Pt / C) for ORR. As depicted in FIG. 5b, the exposed planes of Pt viz (111), (200), (220), (311), and (222) at 29 values of 39.76°, 46.24°, 67.45°, 81.28°, and 85.70° aligns with the cubic structure of Pt having a space group ofFm3m space group (JCPDS: No:00-004-0802) and aligns with face centered cubic (fcc) crystallographic arrangement. The prominent metallic features of decorated Pt nanoparticles were derived from the exposed planes of the platinum. An increased broadening (FIG. 5c) of the planes corresponding to Pt confirms the decreased crystalline size of the same since the concerned support is primarily amorphous in nature (ref) in the aspects of Pt / SiO2@CeO2-30% in comparison with that of the Pt / SiO2. This observation further strengthens the interpretations in regard of the anchoring effect of Ce which was raised earlier in the light of conclusions observed from earlier in the TEM images (FIG.2).

[0158] A comparative analysis of dispersion characteristics of Pt nanoparticles over SiO2@CeO2 and SiO2 highlights the role of Ce in affirming a finer dispersion of Pt nanoparticles over the substrate, as observed by the increased broadening (FIG. 3c) and decreased crystalline size of Pt / SiO2@CeO2-30%, which is further supported by the TEM data shown in FIG.2.

[0159] Microstructural defects and vacancies was derived from the Raman analysis. Observed features in FIG. 5d and FIG. 5e depict a prominent band in the range of 460 cm-1and shoulder band in 600 cm-1. The intense, sharp vibrational band observed around 460 cm-1is assigned as a signature band corresponding to CeO2 which can be further attributed to F2gphonon band of CeO8unit, confirming the cubic fluorite structure reinforcing the interpretations turned out from XRD (FIG. 5a-c) analysis. Initial understanding owing to the size controlled and engineered formation of nanoceria with prominent oxygen vacancy defects has been pronounced sharply in the obtained Raman spectra. As concluded from FIG. 5d, presence of CeO2nanoparticles over the surface of SiO2is evident as the prominent band (F2g) corresponding to CeO2is profoundly present in the obtained Raman spectra. Evaluation of SiO2@CeO2-10% and further moving on to SiO2@CeO2-40%, there is a notable increment in the features corresponding to CeO2which can be further attributed to the increased coverage of CeO2over SiO2spheres. Presence of the F2gband is evident in 10, 30, and 40 Wt. % CeO2decorated SiO2which is absent in SiO2, this further slants to the presence of CeO2nanoparticles over SiO2spheres. The shoulder peak observed at 600 cm-1(D) is directly attributed to the presence of Ov (oxygen vacancy) defects in the system. The scientific requirement for the size-controlled establishment of CeCh to attain exceptional contributions from oxygen defects can be pointed out from the presence of this peak, corresponding to the Ov defect in SiO2@CeO2-30%. This observation substantiates the suitability of SiO2@CeO2-30% for the dispersion of platinum nanoparticles. Divergencein the microstructural and defect features after Pt decoration was analyzed as depicted in FIG. 5e. Observed features corresponding to CeO2is retained even after Pt decoration. Leaning on to the evidences extracted from the Raman spectra, EPR studies were done which further shows the presence of VO building up over foundation of an increment in the intensity lining up within SiO2@CeO2-30% (FIG.5f).

[0160] Example 3: Comparative X-ray Photoelectron Spectroscopy (XPS) Analysis of oxidation states in inventive and conventional electrocatalyst

[0161] Table 1: The percentage contribution of different oxidation state of Pt from the XPS analysis.

[0162] Atomic Atomic Atomic Sample percentage of Pt percentage of Pt percentage of Pt (0) (2+) (4+) Pt / SiO2@CeO2- 52.68% 20.09% 27.22% 30%

[0163] Pt / SiO240.66% 39.69% 19.65% Pt / C 39.2% 32.98% 27.78%

[0164]

[0165] The electronic redistribution of Pt nanoparticle has been compared in Table 1. The inventive sample Pt / SiO2@CeO2-30% reflects an increase metallic Pt state (0) in Pt comparison with that of Pt / SiO2spectra. The emergence of a dominant metallic state for Pt (0) nanoparticles account for the increment in the ORR kinetics as this reinforces the aspect of metal support interactions. Compared to Pt / C and Pt / SiO2, the CeO2Pt interface created over SiO2spheres in the inventive sample provides a strong support to metal interaction. The electronic interaction between CeCh and Pt enhances the transfer of electrons from Ce3+to Pt species making the availability of Pt (0) state much higher compared to Pt / C and Pt / SiO2 because of comparatively lower interaction.

[0166] Example 4: Comparative electrochemical properties:

[0167] A slurry was prepared by dispersing 5 mg of the catalyst in 1000 microliters of water and ethanol each. The obtained slurry was sonicated to ensure proper dispersion of the catalyst, followed by drop casting over a glassy carbon (GC) working electrode having a geometricsurface area of 0.196 cm2, which was further dried under an IR lamp. For comparison, a slurry of 40 Wt.% Pt / C was also prepared by dispersing 5 mg of the catalyst in a mixture of 750 microliters of water, 250 microliters of IPA, and 40 microliters of the 5% Nafion solution. The loading of Pt over the GC electrode was fixed as 20 micrograms for both catalysts. All the measurements were performed in a three-electrode setup using 0.1 M HCIO4 solution as the electrolyte, the catalyst-coated GC as the working electrode (WE), Ag / AgCl as the reference electrode (RE), and a graphite rod as the counter electrode (CE). All the electrochemical studies were performed in a Biologic potentiostat (Model No: SP-300) combined with a Pine Research RDE / RRDE unit.

[0168] Evaluation of the ORR activity of the prepared catalysts is carried out via aiding the conclusions deduced from the adopted techniques viz, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) by utilizing rotating disc electrode (RDE) techniques. The contribution of CeO2in regard of the percentage of defective ceria (Ce3+) and the fraction of VO towards an establishment of superiority in the ORR activity has been inferred electrochemically.

[0169] The evaluation of the single electrode studies was availed using a three-electrode setup (Half fuel cell analysis, refer FIG. 10a in which a catalyst coated glassy carbon electrode was used as the working electrode (WE), graphite carbon rod as the counter electrode (CE), and Ag / AgCl as the reference electrode (RE). The obtained CV profiles of Pt / SiO2, Pt / SiO2@CeO2-10%, Pt / SiO2@CeO2-30% and Pt / SiO2@CeO2-40% was compared with the state-of-the art (Pt / C) catalyst for ORR. Characteristic features typical to Pt in 0.1 M HCIO4 are observed in the obtained CV profiles depicted in FIG. 6a. The redox features observed in the potential region ranging from 0.0 V to 0.30 V are typically correlated to the underpotential hydrogen adsorption and desorption characteristics (ref) of Pt based materials. The observations in regard of the electrochemically active surface area (ECSA) were obtained from the associated hydrogen desorption region.

[0170] The ORR activity is significant as observed from the obtained LSV profiles (FIG. 6b), augmenting trends are observed in the values of onset potential (Eo) (0.940 V vs. RHE) and the half wave potential (E1 / 2) (0.840 V vs. RHE) of Pt / SiO2@CeO2-30% in comparison with that of Pt / C and the other counter catalysts. The observed trend in the Eo and E1 / 2 follows an order of Pt / SiO2@CeO2-30% > Pt / C> Pt / SiO2@CeO2-10% > Pt / SiO2@CeO2-40% >Pt / SiCh. The contribution of prominent amount of Ce3+in SiO2@CeO2-30% towards a promising hike in the kinetics of ORR can be accounted by the electronic redistribution between Pt and Ce3+.

[0171] Enhanced metallic feature of Pt in Pt / SiC @CeO2 -30% plays a vivid role in the improvisation of the ORR kinetics relative to Pt / C and Pt / SiO2. These conclusions further grounds the assumptions availed in regard of metal support interaction arising from SiO2@CeO2 support. A better understanding owing to the rate of kinetics involved is evidenced from the observations trailed out from the Tafel analysis of the synthesized catalysts. As observed in FIG. 6c, the existence of a lowest value of the Tafel slope for Pt / SiO2@CeO2-30% (49.1 mV dec1) compared to other catalysts pointing on to the fastest ORR kinetics further strengthens the observations availed prior in the aspects of metal support interaction aligning with the take away from obtained XPS spectra.

[0172] Mass activity (jk, mass) and specific activity (jk, specific) was calculated at 0.85 V and was further normalized with the loading of Pt and obtained value of ECSA respectively. As observed, FIG. 6d of Pt / SiO2@CeO2-30% is better in regard of mass activity and specific activity. In comparison with the state -of- the- art catalyst Pt / C, Pt / SiO2@CeO2-30% shows a mass activity (201.8 A mg-1Pt) of 1.8 times higher and a specific activity (0170 mA cm-2Pt) of 4.4 times higher. Observed increment in the aspects of mass activity and specific activity turns out to be a consequence of increased metal support interaction and electronic redistribution involved via the presence of Ce3+states. Improved value of the mass activity at 0.8 V turns out to the conclusion that ORR is controlled by both kinetic and diffusion process.

[0173] Based on the initial electrochemical analysis of the synthesized materials, it has been figured out that Pt / SiO2@CeO2-30% shows a better activity in the aspects of Eo, E1 / 2, mass activity and specific activity.

[0174] Example 5: Rotational ring disk electrode (RRDE) studies

[0175] Rotational ring disk electrode (RRDE) studies were carried out for the confirmation of the involved ORR catalytic pathway and the percentage of H2O2 produced as a payoff of the parasitic reactions which is primarily a two electron electro reduction process. A potential of 1.2 V vs. RHE was applied to estimate the percentage of H2O2 formed. Estimation wascarried out via the calculation of ring current having a collection efficiency of 37% at varied disk potentials. The obtained results confirmed that the most favored pathway is 4-electron and the amount of H2O2 is produced is negligible apparently less than 4% which minimizes the probability of the poisoning effects from H2O2. Leaning on to the derived conclusions from RRDE analysis, Koutecky-Levich (K-L) plot was constructed which could further aid in to the continuation of analysis in the aspects of ORR pathway involved. As per plot of 1 / j vs. 1 / ω1 / 2which was derived from information’s turned out from the obtained LSV profiles at different speed of rotations shows an inclination towards a 4-electron pathway strengthening the outputs derived from RRDE analysis. Effective ability of CeO2based compounds towards removal of noxious free radicals further turns out favourability of same towards 4e-0RR pathway.

[0176] Accordingly, Pt / SiO2@CeO2-30% seems to show enhancement in ORR kinetics which was further considered as a base for the studies regarding the adsorption properties of oxygen in comparison with that of state-of-the-art Pt / C catalyst. The enhanced availability of oxygen deficiency sites in SiO2@CeO2-30% and the further augmentation of VO observed as an effect of Pt incorporation leaning on to the observed oxygen spillover further induces the formation of the oxygen deficiency sites for the adsorption of oxygen which can be pointed as a key tool for enhancement of ORR kinetics. Dominating extent of variable valance states in CeO2 (Ce3+and Ce4+) is reported to offer an enhancement in the oxygen storage and further associated mobility which seems to lend support for an enhanced ORR dynamic. Enhancement in the adsorption properties of the oxygen is analysed by reductive stripping curves as depicted in FIG.6e. The adsorption properties of the oxygen have been obtained in the catalytic surface by CV profiles recorded at varying potentials from 0.3 to 1.5 V vs. RHE as depicted in FIG. 6e. Followed by this the area of the Pt-0 desorption curves associated has been integrated followed by the normalization using the obtained ECSA values. The calculated values are further plotted against the applied potential as depicted in FIG. 6f. An enhanced slope further points out towards an enhanced oxygen adsorption characteristics and hence a better oxygen storage-release property.

[0177] The selection of SiO2 as a substrate for nano CeO2 and Pt nanoparticles for an improved stability in the aspects of textural endurance owing to an increased resistance towards the support corrosion. Conclusive evidence owing to support stability is confirmed via an accelerated stress test (AST) of 5000 cycles in which the cycling potential was maintainedbetween 1.0 to 1.5 V vs. RHE aiming at creation of a triggered environment for the support corrosion. The comparative CV plot for Pt / SiO2@CeO2-30% and Pt / C in the aspects of AST protocols reveals the percentage degradation obtained after the AST protocol. The clear degradation of ECSA in Pt / C by a scale of 57% is noticed as an outcome of the suspected support corrosion and allied particle agglomeration. Meanwhile subsequently minimal drop of ECSA in Pt / SiO2@CeO2-30% ensures the endurance offered by the non-carbonaceous support. In agreement with the observations from the CV profiles, trends in the LSV plots shows a comparable outcome as that of the conclusions figured out from the CV plots obtained. The observed decrement of ORR activity in the aspects of Eo, E1 / 2 and limiting current is evident in Pt / C while the persistence of these intrinsic parameters is observed in Pt / SiO2@CeO2-30%.

[0178] The TEM images obtained post durability and the corresponding elemental mapping confirms the structural integrity of the non-carbonaceous support. As deduced, the consequent agglomeration of Pt nanoparticles after the corrosion studies are evident in the post TEM image of Pt / C. Meanwhile perseverance of the interconnectivity of Pt nanoparticles and integrity of the supports confirms the resistance towards support corrosion in triggered environment turning out to be a scientific explanation for the minimal degradation of the ORR activity of Pt / SiO2@CeO2-30% as compared to state- of -the- art Pt / C.

[0179] Example 6: Membrane Electrode Assembly (MEA) fabrication and Fuel cell testing:

[0180] To test the fuel cell, a membrane electrode assembly (MEA) was constructed by sandwiching a Nafion-HP membrane (Dupont) with gas diffusion electrodes (GDE). The GDEs were prepared by brush-coating the catalyst slurries onto the gas diffusion layer (GDL). The catalytic slurry, used for brush-coating, was made by dispersing the catalysts (Pt / SiO2@CeO2-30% for the cathode and Pt / C 40% for the anode) in a solution of isopropyl alcohol and water, using a probe sonicator for thorough mixing. To serve as both ionomer and binder, a specific amount of Nafion solution (20%) was added, achieving an ionomer-to-catalyst support ratio of 0.3. The catalyst loading was kept at 0.5 mg / cm2. This slurry was uniformly applied to the GDL using a ponytail brush at 40 °C, and after coating, the GDL was vacuum-dried at 120 °C. The MEA was then assembled by hot-pressing the catalyst-coated GDLs around a Nafion membrane at 130 °C with a load of 1.0 t for oneminute. The completed MEA, with an active area of 9 cm2(3 cm x 3 cm), was mounted into a single-cell fixture (Fuel Cell Technologies, Inc., USA) using a torque of 3 N m. This fixture was connected to a fuel cell test station (Fuel Cell Technologies, Inc., USA) for cell analysis. During testing, humidified gases were supplied to both electrodes without backpressure. Once the open-circuit voltage (OCV) stabilized, the MEA was activated at 0.40 V to reach maximum current output, with the fuel cell fixture held at 60 °C. Measurements, including current (I) - voltage (V) polarization curves, were taken following standard procedures for MEA activation and data collection.

[0181] Grounding on to the established conclusions from the half-cell analysis, Pt / SiO2@CeO2-30% has been confirmed as a better catalyst with promising opportunities. Scope of establishing the inherent traits of this ORR catalyst on to single cell analysis in PEMFC and further studies has been taken under consideration. The membrane electrode assembly (MEA) was prepared by aiding gas diffusion electrodes (GDE) and a proton exchange membrane (as explained above). Establishment of an HOR (hydrogen oxidation reaction) catalyst at anode was availed via incorporation of Pt / C and Pt / SiO2@CeO2-30% was explored in the cathode, and the potential of the same as an ORR catalyst with an incorporation of exciting scientific domains was explored in the scenario of applicational aspects in a device level. Insightful outputs pertaining to the peculiar properties were obtained from the recorded polarization curves both in th-Air and H2-O2 feed conditions. The contribution of SiO2 in water retention properties, and nano CeO2 towards oxygen buffering behavior has been taken under consideration. Scientific aspects of these peculiar properties were further analyzed based on the outputs furnished from the single cell PEMFC analysis (or full cell PEMFC, refer FIG. 10b). Comparative studies on Pt / SiO2@CeO2-30% support was conducted against a standard Pt / C based MEA, where state- of -the- art Pt / C was employed as both anode and cathode catalyst. Substantially enhanced performance was observed for Pt / 30%SiO2@CeO2 in th-Air feed environment compared to that of the state- of- the-art Pt / C. These device-level results highlight the practical applicability of earlier scientific observations.

[0182] As inferred from FIG. 7, Pt / SiO2@CeO2-30% shows a contact angle value of 28.4° confirming the hydrophilicity of the material in comparison with that of Pt / C where the observed contact angle value is 88.4°. Inclining towards the observations obtained from the contact angle measurements, optimum percentage of relative humidity was observed to be40% to 45% for Pt / SiO2@CeO2-30% based MEA and 95% to 100% for the state-of-the-art Pt / C based MEA. This is concluded from the recorded polarization plots in and H2— Air feed conditions. The effect of water retention properties of SiCh is validated from the analysis of the obtained performance in regard of the Pt / SiO2@CeO2-30% in 40% RH and 60% RH. Derived outcomes from the obtained results reveals a better activity in 40% RH of Pt / SiO2@CeO2-30%. FIG. 8a and FIG. 8b depicts the comparative polarization plot of Pt / C and Pt / SiO2@CeO2-30% in H2-O2 and H2-Air feed conditions respectively. The observed shrinkage in H2-Air feed conditions is in consideration with the mass transfer effects which is known to be observed when shifted from O2 to Air. Dominating performance observed by Pt / SiO2@CeO2-30% in air fed environment compared to that of Pt / C establishes the effect of nano CeO2having increased amount of VO which was priorly concluded from XPS, Raman and EPR analysis. The obtained value of current density at 0.6 V (which is practical operating potential of fuel cell) in H2-Air reactant medium is 0.68 A cm-2and 0.5 A cm-2for Pt / SiO2@CeO2-30% and Pt / C, respectively (FIG. 8b). The observed superiority of Pt / SiO2@CeO2-30% is validated throughout the polarization curve including activation, ohmic and mass transfer regions. The evidenced particular effect of Pt / SiO2@CeO2-30% in oxygen lean conditions and the inherent oxygen storage capacity of the nano CcCh is validated by the comparative analysis of performance obtained in H2-O2 fed environment for both the cathode catalysts employed. A comparable performance was obtained in H2-O2 fed conditions for both Pt / SiO2@CeO2-30% and Pt / C based MEAs. The observed current density at 0.6 V in H2-O2 environment is 1.00 A cm-2and 0.94 A cm'2for Pt / 30%SiO2@CeO2 and Pt / C based MEA’ s respectively (FIG.8a). Leaning on to this, the peculiarity of nano CeO2to act as an oxygen storage material in oxygen rich conditions and making the same available at oxygen lean conditions is validated in practical applications of PEMFCs. Observed trend of increased losses in the polarization plots over the whole current density region in H2-Air fed conditions as compared to H2-O2 is attributed to the nitrogen blanketing effect and the decreased partial pressure of oxygen aligning with the comparatively lower percentage composition of O2 in Air (100% in oxygen and 21% in air). This is further analyzed via the observed drop of voltage when moving from oxygen to air (Voxygen -Vair) for both the carbon based and CeO2based catalysts. As concluded from the FIG.8c, comparative voltage declination profile of Pt / SiO2@CeO2-30% and Pt / C based MEA’s at constant current densities reveals a comparatively curtailed drop in Pt / SiO2@CeO2-30% while the same is much significant in Pt / C based MEA. Usually whenshifting from oxygen to air there will be decline in the observed performance since the partial pressure of oxygen in air is only 20%. Here the voltage drop is calculated for the catalyst with respect to the shift from oxygen to air, and it has been seen that the drop is more for the state of the art Pt / C rather than the present catalyst because of the oxygen enrichment provided by the observed oxygen vacancies in the present catalyst. The implication of the same is understood from the observed deviation of the current densities at the usual operating potential i.e. 0.6 V. The percentage drop of current density observed for Pt / SiO2@CeO2-30% (FIG.8d) is only 30.80% while the same is 48.19% for Pt / C based MEA on a dilution of oxygen concentration from 100% to 21%. The obtained trends in the aspect of performance are scientifically supported by further analysis aiding the electrochemical impedance spectroscopy (EIS). The attained charge transfer resistance (RCT) at an operating potential of 0.6V measured in H2-Air environment conveys a promising trend leaning on to the conclusions obtained so far. Comparatively smaller RCT is observed in Pt / SiO2@CeO2-30% (0.175 Ohm cm-2) while the state-of-the-art Pt / C based MEA shows a RCT value of 0.284 Ohm cm-2which is 1.6 times higher than the RCT offered by CeO2 based catalyst. The obtained validation is further supported by the measured EIS spectra at 0.8 V which neglects the possibility of loop hole creation at 0.6 V in regard of the mass transfer effects. Validation regarding the oxygen release properties of the availed catalysts in the light of EIS spectra is analyzed by the observed increment in the RCT values upon varied reactant fed conditions viz H2-O2and H2-Air. As observed from Table 2, comparatively reduced increment observed in Pt / SiO2@CeO2-30% when shifting from oxygen rich condition to oxygen lean condition. The observed trend is followed at 0.8 V and 0.6 V. Reduced increment of resistance is better because as the increment is less, it will be contributing lesser towards the hindrance parameters of the reaction kinetics.

[0183] Table 2: The EIS values of the MEAs at different potentials and feed conditions

[0184] Feed Gas H2-O2H2-Air Rct Air-Rct Oxygen (Ohm cm2) H2-O2H2-Air Rct Air-Rct Oxygen (Ohm cm2) Rct at 0.8 V (Ohm cm2) Rct at 0.6V (Ohm cm2)

[0185] (Ohm cm2) (Ohm cm2)

[0186]

[0187] Pt / SiO2@CeO2- 0.288 0.515 0.227 0.139 0.174 0.035 30%

[0188] Pt / C 0.328 0.769 0.441 0.234 0.283 0.048

[0189]

[0190] Example 7: Stability tests

[0191] The stability aspects of the synthesized Pt nanoparticles embedded on to the carbon free SiO2@CeO2 bed had been investigated. Based on the observations from the half-cell analysis and the corrosion studies availed, a better understanding of catalyst stability in the triggered corrosive environment of PEMFC has been achieved. Degradation of ECSA value in the solid-state CV was taken as a tool for analysis of the stability of the catalyst. Degradation rate of the ECSA was analyzed via aiding an AST protocol. A start-stop cycling protocol was involved by cycling the MEA in the potential range of 1.0V-1.6V at a scan rate of 500 mV sec-1maintaining the cell an operational temperature of 70 °C with hydrogen flow at anode and nitrogen flow at cathode. Prior to the employed AST cycles CV was taken in a potential range of 0.05V - 1.0V at a scan rate of 50 mV sec-1. Subsequently the embedded MEA inside the fixture went through 5000 AST cycles availing the potential requirement mentioned above for the AST cycles. Upon completion of these AST cycles another CV was taken to avail an understanding regarding the degradation observed in the ECSA values. Post AST measurement of CV confirms the consistency in the observed ECSA value of Pt / SiO2@CeO2-30% with a minimal decrement. While the state-of-the-art Pt / C based MEA was observed to show a degradation leaning on to the decrement of ECSA value. Obtained observations demonstrate a better stability offered by Pt / SiO2@CeO2-30% in comparison with that of Pt / C based as depicted in FIG.9.

[0192] ADVANTAGES OF THE INVENTION:

[0193] • The electrocatalyst of the present invention has a structure that enables complete coverage of the support spheres using platinum nanoparticles which in turn enhances conductivity by mitigating the electrical inertness of the SiO2 support. This approach aligns with the intended design of fully coating the support spheres with platinum to improve conductivity.

[0194] • The unique interconnected Pt nanoparticle network of the electrocatalyst demonstrates improved durability by reducing susceptibility to migration,dissolution, and agglomeration, further supporting the objective of forming a continuous network of Pt nanoparticles.

[0195] • The electrocatalyst is efficient and useful for both Low temperature LT and high temperature HT fuel cell(s) and provides higher stability and durability to the fuel cells.

[0196] • The electrocatalyst avoids or lessens sluggish kinetics, hence, better ORR performance thus increasing fuel cell performance and stability particularly in air due to the inherent oxygen vacancies and hence the oxygen storage and release property.

Claims

We Claim:

1. An electrocatalyst for oxygen reduction reaction (ORR) comprising,(i) at least one metal Ml selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof;(ii) at least one metal oxide M2 selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;(iii) a catalyst support selected from silicon dioxide (SiO2), zirconium oxide (ZrO2), titanium oxide (TiO2), and aluminum oxide (Al2O3), or any combination thereof;wherein the metal Ml is anchored onto the catalyst support coated with the metal oxide M2.

2. The electrocatalyst as claimed in claim 1, wherein weight % of metal Ml is in the range of 45-55% based on weight % of the support and the weight % of the metal oxide M2 is in the range of 10-40 % based on the weight % of the support.

3. The electrocatalyst as claimed in claim 1, wherein the particle size of metal Ml is in the range of 3-5 nm and the particle size of the metal oxide M2 coated on the catalyst support, is in the range of 5-10 nm.

4. The electrocatalyst as claimed in claim 1, wherein the catalyst support comprises particles in spherical shape with a diameter in a range of 400 nm - 450 nm.

5. The electrocatalyst as claimed in claim 1, wherein the electrocatalyst is crystalline having oxygen vacancy defects.

6. The electrocatalyst as claimed in claim 1, wherein the electrocatalyst is carbon free.

7. An electrocatalyst for oxygen reduction reaction (ORR) comprising platinum metal nanoparticles anchored to a catalyst support coated with a metal oxide wherein the catalyst support is spherical particles of silicon dioxide and the metal oxide is cerium oxide.

8. The electrocatalyst as claimed in claim 7, wherein the weight of cerium oxide is 10%, 30% or 40% based on the weight of the silicon dioxide.

9. A process for preparing an electrocatalyst for an oxygen reduction reaction (ORR), comprising the steps of:a) preparing a catalyst support comprising spherical particles of a support selected from silicon dioxide (SiO₂), zirconium oxide (ZrO₂), titanium oxide (TiO₂), and aluminum oxide (Al₂O₃), or any combination thereof;b) coating a metal oxide M2 onto the support of step a) by ethylene glycol assisted method wherein the metal oxide M2 is selected from the oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;c) loading a metal Ml onto the M2 metal oxide coated onto the support by polyol- assisted reduction method to obtain the electrocatalyst wherein the metal Ml is selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof.

10. The process as claimed in claim 9, wherein the polyol assisted reduction method comprises dissolving a metal Ml precursor in a reducing agent wherein the Ml precursor is selected from a salt, an acid, a halide, a haloacid, acetyl acetonate salt or any combination thereof and the reducing agent is selected from urea, sodium hydroxide (NaOH), potassium hydroxide (KOH), and hydrogen peroxide (H2O2) or any combination thereof.

11. A half-fuel cell for a proton exchange membrane fuel cell (PEMFC) comprising:i. an electrocatalyst comprising:at least one metal Ml selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof;at least one metal oxide M2 selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;a catalyst support selected from silicon dioxide (SiO2), zirconium oxide (ZrO2), titanium oxide (TiO2), and aluminum oxide (A12O3), or any combination thereof; wherein the metal Ml is anchored onto the catalyst support coated with the metal oxide M2;ii. working electrode,iii. reference electrode,iv. counter electrode,v. power supply, andvi. electrolyte solution;wherein said electrocatalyst is coated or decorated onto said working electrode.

12. A full fuel cell for a proton exchange membrane fuel cell (PEMFC) comprising:i. an anode,ii. a cathode,iii. a proton exchange membrane,iv. an electrocatalyst comprising:at least one metal Ml selected from nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds) or any combination thereof;at least one metal oxide M2 selected from oxide of cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and ytterbium (Yb) or any combination thereof;a catalyst support selected from silicon dioxide (SiO2), zirconium oxide (ZrO2), titanium oxide (TiO2), and aluminum oxide (A12O3), or any combination thereof; wherein the metal Ml is anchored onto the catalyst support coated with the metal oxide M2; andv. a gas diffusion layer; wherein said electrocatalyst is coated or deposited onto said gas diffusion layer.

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