Stabilized platinum fuel cell catalyst and preparation method thereof

Abstract

The disclosure describes a method of stabilizing a carbon supported noble metal catalyst by selective metal oxide deposition on the carbon support of the catalyst by a vapor deposition process. The method includes the flowing steps: a) Providing a carbon supported noble metal catalyst, b) Forming a blocking layer over an exposed surface of the noble metal on the catalyst, c) Exposing the catalyst to a gas containing metal organic compounds to absorb the compounds selectively to the carbon support, d) Exposing the catalyst to an oxidant to form a metal oxide on the catalyst carbon support, e) Repeating steps c) and d) sequentially for one to ten of cycles, preferably one to five cycles, f) Removing the blocking layer from the catalyst to re-expose the noble metal catalyst surface.

Description

[0001] STABILIZED PLATINUM FUEL CELL CATALYST AND PREPARATION METHOD THEREOF

[0002] Cross Reference to Related Applications

[0003] This application claims the benefit of priority to US Provisional Patent Application No. 63 / 569,493, filed March 25, 2024, the entire contents of which are incorporated herein by reference.

[0004] Technical Field

[0005] The technical field is platinum group metal catalyst, in particular for hydrogen oxidation reactions (HOR) and oxygen reduction reactions (ORR).

[0006] Background Art

[0007] Platinum group metal (PGM) nanodot catalysts are key materials for new energy conversion and used as a catalyst. Platinum on Carbon (Pt / C) catalyst, for example, is widely applied for polymer electrolyte fuel cells (PEMFCs), which are devices generating electric power using hydrogen and oxygen via hydrogen oxidation reactions (HOR) and oxygen reduction reactions (ORR). Wide varieties of fuel cell (FC) applications are considered, for example, automotive, railway, ship, heavy machine, and stationary fuel cells for residential and industrial applications. The main hurdle of these PGM catalysts is their material cost, so it is necessary to reduce the cost of those catalysts, like reducing the loading amount of PGM on the catalyst, and / or extending the lifetime of the catalyst. However, the degradation of Pt catalyst activity cannot be avoided, because the Pt / C catalyst is exposed to harsh conditions during FC operation and start-stop, such as, high potential, low pH, and oxidation and reduction reaction of Pt in the nanodots. Those severe conditions lead to Pt nanodot dissolution, migration, agglomeration, and detachment; and also corrosion of the carbon substrate. As a result, the catalytically active surface area of the Pt nanodots on the catalyst is decreased, and activities of Pt / C catalyst are degraded. This degradation of Pt / C catalyst activity is the subject of intensive efforts to define mitigating strategies to prolong the lifecycle of such catalysts. One general area of research is the use of metal oxides to coat Pt / C catalyst material, to coat the Carbon support prior to Pt nanodot formation, or to selectively coat Pt / C catalyst material on the Carbon portion to thereby “cage” the Platinum nanodots (also termed “nanotraps”), thereby reducing migration and agglomeration. In each case, ideally the Platinum nanodots adhere to the metal oxide to reduce detachment losses (anchoring). ZrOx, TaOx, TiOx, and CoOx metal oxides have been used previously for this reason.

[0008] The following disclosure provides an improved caging method for reducing migration, agglomeration and detachment of Pt nanodots on carbon, but may be applied more generally to PGM catalysts on other support materials.

[0009] Summary of Invention

[0010] The invention may be understood in relation to the following embodiments:

[0011] Disclosure of Invention

[0012] This disclosure relates to a method for caging PGM deposits on a support. The general process will be described in relation to Pt / C catalysts as the main example. The general process for caging Pt nanodots on Carbon are:

[0013] • Deposit the Pt nanodots on the Carbon support.

[0014] • Selectively block the surface of the Pt nanodots with a blocking agent that forms a layer on the Pt nanodots, but not on the Carbon support.

[0015] • Use a vapor phase deposition process to form a metal oxide layer on the Carbon support only (selective deposition), with the Pt nanodot surfaces blocked from the deposition process by the blocking agent. This is the caging or nanotrap step.

[0016] • Remove the blocking agent to expose the catalytically active Pt nanodot surface.

[0017] The state of the art has well established means for Pt nanodot formation on Carbon supports. Some methods are electrochemical depositions, some are vapor phase depositions, and there are other processes also described in the art. See, e.g., Chen, Aicheng, and Peter Holt-Hindle. "Platinum-based nanostructured materials: synthesis, properties, and applications." Chemical reviews 110.6 (2010): 3767-3804. The method described herein is applicable to the resulting Pt / C material regardless of the Pt / C manufacturing process as long as the Pt is in the form of discrete depositions such as nanodots on the Carbon support material.

[0018] In general, the vapor phase deposition is preferably atomic layer deposition (ALD). ALD enables thinner and uniform metal oxide formation than chemical vapor deposition or other techniques. Further, ALD is the best form of vapor phase deposition for use in conjunction with blocking agents to selectively coat targeted areas or materials of a substrate, such as the Carbon support material of Pt / C catalysts. This is classified in the art as Area-Selective Atomic Layer Deposition (AS- ALD). See, generally, Cao, Kun, et al. "Catalysts design and synthesis via selective atomic layer deposition." Journal of Vacuum Science & Technology A 36.1 (2018). The process described herein is an AS-ALD process.

[0019] The metal oxide is selectively deposited on the Carbon support, by AS-ALD normally, to thereby fill in the gaps between Pt nanodots with metal oxide material. This filler metal oxide layer physically blocks the Pt nanodots from migrating along the Carbon support surface and eventually agglomerating. Interactions between the Pt the metal oxide and the Carbon also stabilize the Pt nanodots in place, reducing the rate of nanodot detachment. Several metal oxides are suitable for use as ALD deposited caging material, in particular ZrOx, TaOx, TiOx, CoOx and NbOx metal oxides. These metal oxides have well-established ALD processes and can form stable surface coatings on Carbon. If the metal oxide nanostructure is too thin, the effect of nanodot caging is limited, so that the migration of nanodots cannot be prevented. If the metal oxide is too thick, the Pt nanodot is eventually covered by metal oxide, and the catalytic activity is reduced because the active area on the Pt nanodot becomes smaller. The thickness or the size of the metal oxide nanostructure will depend on the size of the Pt nanodots but can be in a range of about 1 nm or less, about 0.5 nm or less, or about 0.3 nm or less. The total process time of metal oxide ALD should be minimized, or the migration of Pt nanodot occurs during the ALD process because the Pt / C catalyst is heated during the ALD process. Thus, metal oxide ALD is better if performed using a metal oxide precursor with a growth per cycle that minimizes the number of ALD cycles required to reach at targeted metal oxide thickness. The preferred metal oxide is NbOx formed using Cyclopentadienyl(diethylamido)(tert- butylimido)niobium) or (diethyamido)(tert-butylimido)bis(tert-butoxy)niobium), which is experimentally demonstrated below.

[0020] Blocking agents are a functionally defined category of chemicals. Currently, the main chemical group of blocking agents are self-assembled monolayers (SAMs). Molecules capable of forming SAMs include surface reactive head groups, which have a reactive side and bind to the surface of a substrate, functional tail groups or backbones, which are inert to the surface and usually exposed at SAM surfaces and can be used to tailor the chemical and physical properties of the surface. Provided the density of sites that are reactive with the SAM Monomer head, and that appropriate conditions are used to have the monomer head and such site react, the exposure of the surface to SAM monomer leads to the formation of a SAM monolayer. When the SAM monomers have long tails, they eventually self-align into a grass-like structure. The SAM compounds used for blocking agents can include alkyl aliphatic amines, alkyl aliphatic thiols, and alkyl aliphatic acids with different lengths of linear or branched alkyl chains, which can also include aromatic tails. By modifying the Pt nanodot surface by SAM compounds, the modified surface can obtain high hydrophobicity which prevents the nucleation of ALD precursors. The ideal blocking agent for dry exposure has a high volatility, to enable fast dosage to high developed surface powder in fluidized condition, and a high reactivity towards the Platinum catalyst surface, to maximize inhibitor chemisorption in short time and minimize unexposed surface. With such compatible SAM, fully dry process enables high throughput low cost process in one single manufacturing tool. Blocking agents can be, but not limited to, chosen from the following group: C1 -C30 alkylamines such as oleylamine, dodecylamine, hexadecylamine, octadecylamine, allylamine or other amines, C1-C30 alkylthiols, such as 1 -octanethiol, dodecanthiol, hexadecanethiol, octadecanethiol, and acids, such as linoleic acid, decanoic acid, lauric acid, oleic acid, stearic acid, tetradecylphosphonic acid, and other acids. Oleylamine is demonstrated below as a good blocking agent for the process of this application.

[0021] The blocking agents are removed generally by heating the metal oxide / blocking agent coated Pt / C material anywhere from 50 degrees C to 400 degrees C, in the presence of a controlled concentration of oxygen. Temperature and oxygen concentrations are optimized for the specific blocking agent and Pt / C material to remove the blocking agent while avoiding or sufficiently limiting oxidation of the Carbon substrate (e.g. burning).

[0022] Brief Description of Drawings

[0023] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein: Figure 1A shows the reduction of power density of Pt / C and NbOx caged-Pt / C at 1197 mA cm-2 after 10000 cycles test was 5.5%.

[0024] Figure 1 B shows the reduction of power density of Pt / C and NbOx caged-Pt / C at 1197 mA cm-2 after 10000 cycles test was 1 .0%.

[0025] Mode(s) for Carrying Out the Invention

[0026] Example 1: Wet Oleylamine blocking and NbOx deposition by (diethyamido)(tert-butylimido)bis(tert-butoxy)niobium)

[0027] 3g of 20 wt% Pt loaded Pt / C sample was dipped in 5mM oleylamine in ethanol for 5 hours. After the oleylamine treatment, the sample was rinsed 3 times by ethanol, and then dried using a vacuum desiccator to obtain SAM treated Pt / C catalyst. The Nb20s was deposited by AS-ALD in a homemade fluidized bed ALD reactor at 150 degrees C using (diethyamido)(tert-butylimido)bis(tert-butoxy)niobium precursor and water as the Nb ALD precursor and co-reactant respectively. The ALD cycle for the deposition process was: 1800 second pulse of (diethyamido)(tert-butylimido)bis(tert- butoxy)niobium precursor, 1800 second N2 gas purge, 1800 second water vapor pulse, and 1800 second N2 gas purge. The sequence was repeated three times (i.e. 3 cycles). After the deposition, the oleylamine blocking agent was removed from the platinum surfaces by heating at 200 degrees C in air (i.e. 21 % oxygen) at atmospheric pressure.

[0028] Example 2: Wet Oleylamine blocking and NbOx deposition by Cyclopentadienyl(diethylamido)(tert-butylimido)niobium)

[0029] 1 g of 40 wt% Pt loaded Pt / C sample was dispersed in 50mM oleylamine in ethanol for 5 hours. After the oleylamine treatment, the sample was rinsed 3 times by ethanol, and then dried using a vacuum desiccator to obtain SAM treated Pt / C catalyst. The Nb20s was deposited by AS-ALD in a homemade fluidized bed ALD reactor at 250 degrees C using a Cyclopentadienyl(diethylamido)(tert- butylimido)niobium as the Nb precursor and water vapor as the co-reactant. The ALD cycle for the deposition process was: 360 second pulse of Cyclopentadienyl(diethylamido)(tert-butylimido)niobium precursor, 1800 seconds of N2 gas purge, 360 second pulse of water vapor, and 1800 seconds of N2 gas purge. The sequence was repeated six times (i.e. 6 cycles). After the deposition, oleylamine was removed by heating at 200 degrees C in 10 vol% O2 at 600 Torr. Example 3: Vapor phase (“dry”) Oleylamine blocking and NbOx deposition by Cyclopentadienyl(diethylamido)(tert-butylimido)niobium)

[0030] 1 g of 40 wt% Pt loaded Pt / C sample was filled into the fluidized bed reactor used in Experiments 1 and 3 and the reactor was heated at 140 degrees C. A canister filled with oleylamine was heated to 110 degrees C, kept at a pressure of 38 Torr, and bubbled with 30 seem of N2 gas to supply oleylamine vapor to the fluidized bed reactor for 12 hrs. After the dry oleylamine treatment, the Nb2Os was deposited and the oleylamine was removed as was done in Experiment 2.

[0031] Evaluation of Pt / C Catalyst in Potential Cycle Tests

[0032] In order to check the durability of NbOx caged samples, potential cycle tests were performed using NbOx deposited Pt / C samples prepared by the process of Example 1. Catalyst ink was prepared by mixing NbOx deposited Pt / C samples, ultra- pure water, ethanol, and Nation binder. The catalyst ink was coated on a polymer electrolyte membrane using a spray coater. The Pt loading amount on the membrane was 0.3 mg-cmr2. A membrane electrode assembly (MEA) was prepared using a hot- pressing method. For comparison, another MEA was prepared using Pt / C catalyst without NbOx deposition (Pt / C). These MEA were used for cathode electrodes in PEMFC. The potential cycle test was performed at 80 degrees C with supplying 100 % humidified H2 and 02 at the anode and cathode, respectively. After 10000 cycles, polarization curves were obtained to compare the durability of NbOx deposited Pt / C catalyst and Pt / C catalyst without NbOx. As shown in Figure 1 A and 1 B, the reduction of power density of Pt / C and NbOx-Pt / C at 1197 mA cm-2after 10000 cycles test was 5.5% and 1.0% respectively, which indicate the durability of Pt nanodots is improved by NbOx AS-ALD on Pt / C catalyst.

[0033] Comparison to Literature Examples

[0034] Two references describe caging Pt nanodots using different procedures. These references demonstrate the generic concept from a basic R&D viewpoint, but are not suitable for industrial use.

[0035] • Liu, X., Zhu, Q., Lang, Y., Cao, K., Chu, S., Shan, B., & Chen, R. (2017). Oxide-nanotrap-anchored platinum nanoparticles with high activity and sintering resistance by area-selective atomic layer deposition. Angewandte Chemie, 129(6), 1670-1674.

[0036] The researcher formed Co3O4 / Pt / Al2O3 = Pt nanodots on an Aluminum Oxide support with Cobalt Oxide “caging”. The process was AS-ALD, with the Pt blocked by 1 -octadecanethiol prior to the Cobalt Oxide ALD deposition. Notably, the Cobalt Oxide ALD required 50 cycles to form the caging structure. The Pt / / Al2O3 catalyst is primarily for NOx / Hydrocarbon / CO oxidation. While Pt / / Al2O3 might be stable enough to withstand 50 ALD cycles in a fluidized bed / powder ALD reaction, Pt / C catalyst will be significantly damaged in such a process, by both the extended physical fluidization process and the extended exposure to elevated temperatures and temperature cycles during an ALD process. The researchers did direct AS-ALD on small amounts of catalyst material in a static deposition. The amount of Cobalt precursor chemical required will be cost prohibitive, assuming 50 cycles, and the processing time would be unacceptable, if performed at industrial scale in a fluidized bed / powder reactor. Industrial scale ALD in a fluidized / powder ALD reactor would likely require more than 50 cycles, thus making the industrial process even more economically infeasible.

[0037] • Song, Z., Wang, B., Cheng, N., Yang, L., Banham, D., Li, R., ... & Sun, X. (2017). Atomic layer deposited tantalum oxide to anchor Pt / C for a highly stable catalyst in PEMFCs. Journal of materials chemistry A, 5(20), 9760- 9767.

[0038] Unlike the previous literature example, this paper used Pt / C as a substrate. But like the above literature example, the researchers used small amounts of catalyst material in a static AS-ALD process. “The area-selective deposition of TaOx on OA- Pt / C was carried out in an ALD reactor (Savannah 100, Cambridge Nanotechnology Inc., USA) at 225 °C using tantalum(V) ethoxide (Ta(OC2H5)5) and H2O as precursors, and N2 as the carrier gas.” The researchers used TaOx as the caging metal oxide. The researchers tested 15, 35 and 50 ALD cycles for the TaOx ALD stage of the AS-ALD process. Fifteen cycles was insufficient and 50 cycles started covering the Pt nanodots, whereas 35 cycles appeared to form a good caging structure between the Pt nanodots. Again, in a fluidized powder ALD process at industrial scale, more cycles would be required to achieve the same thickness of TaOx. Even at 35 cycles, the cost of precursors, and the processing time, would make this experimental process infeasible to scale to industrial production. In contrast to these literature examples, this disclosure demonstrates actual fluidized bed reactions for Pt / C catalyst material, using as little as three ALD cycles, that yields caged Pt nanodots with dramatically improved stability. The TaOx / Pt / C reference was for the same type of catalyst and tested their caged catalyst in a potential cycling experiment similar to the above example of this application. At 4700 cycles, peak power density dropped by 12% for the 35 ALD cycle TaOx / Pt / C. In contrast, the three ALD cycle NbOx / Pt / C metal oxide cage material, produced in the above example of this application, only lost 1 % peak power density after 10000 cycles. This is a dramatic and surprising improvement in both the number or ALD cycles and the resulting catalyst stability.

[0039] Industrial Applicability

[0040] The present invention is at least industrially applicable to the production and use of Pt / C catalysts, especially because it proposes a fast, scalable, exposure process with very limited number of cycles.

[0041] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0042] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

[0043] Notation and Nomenclature

[0044] The following detailed description and claims utilize a number of abbreviations, symbols, and terms, which are generally well known in the art, and include:

[0045] • The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.

[0046] • "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms "consisting essentially of" and “consisting of” unless otherwise indicated herein.

[0047] • “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0048] • Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0049] • Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0050] • As used herein, “about” or “around” or “approximately” in the text or in a claim means±10% of the value stated.

[0051] • As used herein, “room temperature” in the text or in a claim means from approximately 20° C. to approximately 25° C.

[0052] • The term “ambient temperature” refers to an environment temperature approximately 20° C. to approximately 25° C.

[0053] • The term “substrate” refers to a material or materials on which a process is conducted. The substrate may refer to a wafer having a material or materials on which a process is conducted or to any high developed surface material potentially serving as catalyst support. The substrate maybe a porous metallic mesh made of Titanium, Nickel, or any other metal, a mesoporous carbon powder, carbon nanofibers, or any other porous carbon support, with or without surface modification. The substrate can be a metal or metal oxide powder. The substrates may be any suitable wafer used in semiconductor, photovoltaic, flat panel, or LCD-TFT device manufacturing. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. For example, the wafers may include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon containing layers (e.g., SiO2, SiN, SiON, SiCOH, etc.), metal containing layers (e.g., copper, cobalt, ruthenium, tungsten, platinum, palladium, nickel, ruthenium, gold, etc.) or combinations thereof. Furthermore, the substrate may be planar or patterned. The substrate may be an organic patterned photoresist film. The substrate may include layers of oxides which are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications (for example, ZrO2 based materials, HfO2 based materials, TiO2 based materials, rare earth oxide based materials, ternary oxide based materials, etc.) or nitride-based films (for example, TaN, TiN, NbN) that are used as electrodes. One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as substrates.

[0054] • Note that herein, the terms “film” and “layer” may be used interchangeably. It is understood that a film may correspond to, or related to a layer, and that the layer may refer to the film. Furthermore, one of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may range from as large as the entire wafer to as small as a trench or a line.

[0055] • The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviation (e.g., Si refers to silicon, N refers to nitrogen, 0 refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).

[0056] • The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to identify the specific molecules disclosed.

[0057] • As used herein, the term “hydrocarbon” refers to a saturated or unsaturated function group containing exclusively carbon and hydrogen atoms. As used herein, the term “alkyl group” refers to saturated functional groups containing exclusively carbon and hydrogen atoms, An alkyl group is one type of hydrocarbon. Further, the term “alkyl group” refers to linear, branched, or cyclic alkyl groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alkyls groups include without limitation, t-butyl. Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclopentyl groups, cyclohexyl groups, etc.

[0058] • As used herein, the abbreviation “Me” refers to a methyl group; the abbreviation “Et” refers to an ethyl group; the abbreviation “Pr” refers to any propyl group (i.e., n-propyl or isopropyl); the abbreviation “iPr” refers to an isopropyl group; the abbreviation “Bu” refers to any butyl group (n-butyl, isobutyl, tert-butyl, sec-butyl): the abbreviation “tBu” refers to a tert-butyl group; the abbreviation “sBu” refers to a sec-butyl group; the abbreviation “iBu” refers to an iso-butyl group; the abbreviation “Ph” refers to a phenyl group; the abbreviation “Am” refers to any amyl group (iso-amyl, sec-amyl, tertamyl); the abbreviation “Cy” refers to a cyclic hydrocarbon group (cyclobutyl, cyclopentyl, cyclohexyl, etc.).

[0059] • Please note that the silicon-containing films, such as Si, SiN, SiO, SiOC, SiON, SiCON, are listed throughout the specification and claims without reference to their proper stoichiometry. The silicon-containing films may also include dopants, such as B, P, As, Ga and / or Ge. The fact that the film contains some residual hydrogen is also omitted from the film composition description. For instance, a SiOC film may contain residual H.

[0060] • Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1 , x=4, and x=any number in between), irrespective of whether the term “inclusively” is used.

[0061] • Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”

[0062] • As used herein, the term “independently” when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR1 x (NR2R3)(4-x), where x is 2 or 3, the two or three R1 groups may, but need not be identical to each other or to R2 or to R3. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.

[0063] • As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0064] • Additionally, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

[0065] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0066] The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise.

[0067] "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms "consisting essentially of" and “consisting of” unless otherwise indicated herein.

[0068] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0069] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0070] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0071] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

Claims

What is claimed is:1 . A method of stabilizing a carbon supported noble metal catalyst by selective metal oxide deposition on the carbon support of the catalyst by a vapor deposition process, the method comprising: a) Providing a carbon supported noble metal catalyst, b) Forming a blocking layer over an exposed surface of the noble metal on the catalyst, c) Exposing the catalyst to a gas containing metal organic compounds to absorb the compounds selectively to the carbon support, d) Exposing the catalyst to an oxidant to form a metal oxide on the catalyst carbon support, e) Repeating steps c) and d) sequentially for one to 10 cycles, preferably one to five cycles, f) Removing the blocking layer from the catalyst to re-expose the noble metal catalyst surface.

2. The method of claim 1 , wherein the vapor deposition process is a sequential gas phase deposition process comprising at least one cycle of exposure of a Niobium metal organic compound and an oxidant, alternately and repeatedly, wherein the metal organic compound is selected from the formula Nb(R1Cp)(=NR2)(NR3)x(OR4)y, wherein each R1, R2, R3, R4can be independently selected from Ci-Ce alkyl chains, linear or branched, where x and y are integer chosen from 0 to 2 and x+y=2, and wherein the oxidant is selected from the group consisting of H2O, alcohol, nitric oxide, nitrogen dioxide, oxygen and ozone, and mixtures of thereof, and where the number of cycles is less than 10.

3. The method of claim 2, where the Nb metal-organic precursor is Cyclopentadienyl(bis(diethylamido))(tert-butylimido)niobium.

4. The method of claim 2, where the Niobium metal-organic precursor is Cyclopentadienyl(bis(methoxy))(tert-butylimido)niobium5. The method of claim 1 , where in the vapor deposition process is sequential gas phase deposition process comprising at least one cycle of exposure of a Niobium metal-organic compound and an oxidant alternately and repeatedly, wherein the metal-organic compounds is selected from the formula Nb(=NR1)(NR2)x(OR3)y, wherein each R1, R2, R3can be independently selected from C1-C6 alkyl chains, linear or branched, wherein x and y are integer chosen from 1 to 2 and x+y=3, and where the oxidant is selected from the group consisting of H2O, alcohol, nitric oxide, nitrogen dioxide, oxygen and ozone and mixtures thereof, and where the number of cycles is less than 5, preferably from one to three cycles.

6. The method of claim 5, where the Niobium metal-organic precursor is (diethyamido)(tert-butylimido)bis(tert-butoxy)niobium.

7. The method of any one of claims 1 to 6, wherein the method further comprises a step of purging the metal organic compounds after step c) and the oxidant after step d) with an inert gas.

8. The method of claims 1-7, where the noble metal catalyst comprises a Pt group metal or a Pt group metal alloy.

9. The method of claims 1-8, wherein the blocking layer is a self-assembled monolayer (SAM), preferably selected from the group consisting of alkyl aliphatic amines, alkyl aliphatic thiols, and acids with different lengths of linear or branched alkyl chains.

10. The method of claims 1-9, wherein the blocking layer is formed by gas exposure of a blocking agent.11 . The method of claim 9, where the blocking agent comprises oleylamine.

12. The method of claims 1 , 2, and 5, wherein the vapor deposition process is performed at a pressure of 0.01 to 100 torr.

13. The method of claims 1 , 2, and 5, wherein the vapor deposition process is performed at a temperature of 50 to 350 degrees C.

14. The method of any of the preceding claims, wherein the vapor deposition process is an atomic layer deposition (ALD) process and the method is an area selective atomic layer deposition process (AS-ALD).

15. A noble metal catalyst, wherein prepared by vapor deposition process according to any one of claims 1 to 14.

16. The method of claims 1-14, wherein the metal oxide is a Niobium Oxide and a second metal is added to the metal oxide layer by introducing one or more additional metal introduction steps during the vapor deposition process.

17. The method of claim 16, where the second metal is selected from the group consisting of Tantalum, Titanium, Zirconium, Molybdenum, Tungsten.

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