supported catalyst

Abstract

A method for preparing a supported catalyst comprising an electrocatalyst on a nitrogen-functionalized carbon support. The method includes providing an electrocatalyst on a carbon support and then incorporating nitrogen into the carbon support to provide a supported catalyst. The nitrogen can be incorporated by exposing the electrocatalyst to gaseous nitrogen.

Description

[Technical Field]

[0001] This specification relates to a method for making supported catalysts, particularly supported catalysts comprising electrocatalysts on nitrogen-functionalized carbon supports, which can be employed in electrochemical devices such as fuel cells or electrolyzers. [Background technology]

[0002] Carbon supports have been modified with nitrogen for use in fuel cells. Zhou, Y. et al. (Energy Environ. Sci. 3, 1437-1446 (2010)) is a review article describing the improvement of Pt and Pt alloy fuel cell catalyst activity and durability by nitrogen-modified carbon supports.

[0003] Orfanidi et al. (Journal of the Electrochemical Society, 164(4) F418-F426 (2017)) reported that the introduction of nitrogen-containing surface groups can optimize the ionomer distribution in the cathode electrode, reducing the voltage loss associated with mass transport at high current densities. The preparation method is said to closely follow that of Jansen et al. (R.J.J. Jansen and van Bekkum, Carbon, 32, 1507 (1994)). Jansen et al. described the amination and ammoxidation of activated carbon by oxidizing the carbon with nitric acid and then subjecting the oxidized carbon to ammonia and ammonia / oxygen gas mixtures at temperatures between 200 and 420°C.

[0004] Ott et al. (Nat. Mater. 19, 77-85 (2020)) describe the control of ionomer distribution in porous carbon-supported catalyst layers for proton exchange membrane fuel cells. Preoxidized carbon is subjected to ammonia decomposition in a tubular furnace under ammonia flow at 200, 400, or 600 °C to produce N-functionalized carbon supports.

[0005] (Journal of Power Sources, Volume 507, 30 September 2021, 229971) report that the N-functional group strongly interacts with phosphate and controls the phosphate distribution in the electrode. The manufacturing method is said to follow Orfanidi et al. (supra).

[0006] Ott et al. (J. Electrochem. Soc. 2022 169) describe the N-functionalization of preoxidized carbon via ammonia at 200, 600, and 800 °C and investigate the mechanisms underlying the performance enhancement associated with nitrogen-modified carbon supports.

[0007] The present invention provides a novel method for producing supported catalysts, including electrocatalysts, on nitrogen-functionalized carbon supports. Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a method for preparing a supported catalyst, comprising the steps of: (i) providing an electrocatalyst on a carbon support; (ii) incorporating nitrogen into a carbon support to provide a supported catalyst, the supported catalyst comprising an electrocatalyst on a nitrogen-functionalized carbon support.

[0009] The resulting supported catalyst is suitable for use in a fuel cell or electrolyzer.

[0010] The method of the present invention uses an electrocatalyst on a carbon support as its starting material, i.e., carbon may be catalyzed to support an electrocatalyst (e.g., electrocatalyst particles) on its surface and / or within its pores, and the carbon support (supporting the electrocatalyst) is then N-functionalized to obtain an electrocatalyst on an N-functionalized carbon support (see FIG. 1a).

[0011] In contrast, known methods (e.g., Jansen et al.) use carbon as the starting material, then oxidize the carbon with nitric acid, N-functionalize the oxidized carbon, and subsequently catalyze the N-functionalized carbon to obtain an electrocatalyst on an N-functionalized carbon support (see Figure 1b).

[0012] The method of the present invention does not require (and preferably does not include) a pre-oxidation step. Having fewer steps can be more efficient and / or economical than conventional methods. Furthermore, pre-oxidation can have certain drawbacks. For example, pre-oxidation can be harmful (e.g., when concentrated nitric acid is used). Pre-oxidation can also affect the porosity of the carbon support (e.g., collapse the pores), reducing the surface area available for supporting the electrocatalyst. Thus, the method of the present invention can allow more catalyst to be placed within the pores of the support.

[0013] The ability to N-functionalize carbon supporting an electrocatalyst is unexpected. Conventional methods require pre-oxidation of the carbon (without an electrocatalyst) to facilitate subsequent N-functionalization. The examples demonstrate that N-functionalization of "fresh" carbon black (i.e., unoxidized and uncatalyzed) is not successful. The inventors have determined that pre-oxidation can be avoided by catalyzing prior to N-functionalization. Without wishing to be bound by theory, the inventors propose that the presence of an electrocatalyst "activates" the carbon support, allowing N-functionalization to proceed.

[0014] According to a second aspect of the present invention there is provided a supported catalyst produced or preparable by the method of the first aspect, the supported catalyst comprising an electrocatalyst on an N-functionalized carbon support.

[0015] It will be understood that the preparation method can be determined by analyzing the supported catalyst product. In particular, it may be possible to determine whether N-functionalization occurred before or after catalysis by examining the distribution of the electrocatalyst and N-functionalization in the carbon support. The catalyst (e.g., Pt particles) is present on the surface and / or within the pores of the support. Without being bound by theory, the inventors propose that the method of the present invention increases the proportion of catalyst within the pores relative to the surface compared to known methods (Figure 1b). Various techniques are available to examine the location of the catalyst on the support. For example, the catalyst can be incorporated into an electrochemical device and then tested under wet and dry conditions. Because N-functionalization is catalyzed by the electrocatalyst, it is expected that there will be more N-functionalization around the electrocatalyst particles, e.g., the N-functionalization will be concentrated around the catalyst rather than uniformly distributed. Various techniques are available to examine the relative location and N-functionalization of the catalyst. For example, samples can be evaluated by TEM (transmission electron microscopy).

[0016] According to a third aspect of the present invention, there is provided a catalyst layer comprising the supported catalyst of the present invention and, optionally, an ionomer.

[0017] According to a fourth aspect of the present invention, there is provided a catalyst-coated membrane (CCM) comprising a catalyst layer of the present invention disposed on an electrolyte (e.g., ion-conducting) membrane. The electrolyte membrane may have a first surface and an opposing second surface, and the catalyst layer may be located on either the first surface or the second surface.

[0018] According to a fifth aspect of the present invention, there is provided a gas diffusion electrode comprising a catalyst layer of the present invention disposed on a gas diffusion layer.

[0019] According to a sixth aspect of the present invention, there is provided a decal comprising the catalyst layer of the present invention and a decal transfer substrate. DETAILED DESCRIPTION OF THE INVENTION

[0020] Provision of electrocatalysts on carbon supports Step (i) involves "providing an electrocatalyst on a carbon support," which can be understood as "providing a precursor comprising an electrocatalyst on a carbon support." The precursor (electrocatalyst on a carbon support) can be a commercially available supported catalyst. For example, carbon black-supported platinum catalysts are available under the HiSPEC™ brand (Johnson Matthey).

[0021] Alternatively, the method of the present invention may include an initial step of catalyzing carbon to obtain a precursor (electrocatalyst on a carbon support). For example, carbon (e.g., carbon black) can be reacted with a platinum salt (e.g., Pt nitrate, HPtCl, or KPtCl) and the platinum reduced to obtain Pt nanoparticles on the surface and pores of the carbon.

[0022] Incorporation of nitrogen into carbon supports The incorporation of nitrogen into the carbon support is sometimes described as N-doping, N-functionalization, or N-modification.

[0023] Typically, incorporating nitrogen into a carbon support involves exposing the carbon support (and associated electrocatalyst on its surface and / or within its pores) to ammonia (NH3). The reaction can occur at standard ambient temperature and pressure (SATP, 25°C, 100 kPa).

[0024] The carbon support may be exposed to a flow of (gaseous) ammonia. For example, the carbon support may be exposed to ammonia at a flow rate of (i) at least 200 mL / min and / or (ii) no more than 800 mL / min. The carbon support may be exposed to ammonia for a period of 2 hours or more, 4 hours or more, or 6 hours or more, and / or the carbon support may be exposed to ammonia for a period of 24 hours or less, 12 hours or less, or 6 hours or less.

[0025] The carbon support may be exposed to ammonia (e.g., a flow of ammonia) at a temperature of 200°C or more, 400°C or more, 500°C or more, 600°C or more, 700°C or more, or 800°C or more, and / or the carbon support may be exposed to ammonia (e.g., a flow of ammonia) at a temperature of 1100°C or less, 1000°C or less, 900°C or less, 800°C or less, 700°C or less, 600°C or less, 500°C or less, 400°C or less, or 200°C or less.

[0026] The carbon support may be exposed to ammonia at a temperature of 500 to 1000° C., for example, 500 to 800° C. or 550 to 750° C. This temperature range is preferred because it promotes the formation of a lattice having both carbon and nitrogen atoms.

[0027] The carbon support may be exposed to ammonia at a temperature of 200-400° C. This temperature range promotes the formation of NHx surface groups.

[0028] Acid treatment The method may optionally include a step of modifying the nitrogen incorporated into the nitrogen-functionalized carbon support. This step may involve changing (preferably increasing) the ratio of pyrrolic N species to pyridine N species incorporated into the nitrogen-functionalized carbon support. Such a step may allow for tuning of the properties of the supported catalyst. The method of the present invention may include a subsequent acid treatment step to modify the N-functionalized carbon support. The acid treatment may include treatment with a mineral acid, such as sulfuric acid (H2SO4), which may result in an N-functionalized carbon support containing oxidized N species along with reduced N species. The acid treatment allows for the desired adjustment of the ratio of these species. For example, the optional acid treatment can adjust the ratio of pyrrolic N species to pyridine N species present in the N-functionalized carbon. The inventors have determined that the level of N-functionalization is maintained after acid treatment, as shown in the examples.

[0029] Electrocatalyst The electrocatalyst is on a carbon support prior to N-functionalization. The electrocatalyst is typically in the form of nanoparticles. The electrocatalyst is preferably (i) platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, and osmium); (ii) gold or silver; (iii) base metals; or (iv) an alloy or mixture containing one or more of these metals or their oxides.

[0030] A preferred electrocatalyst metal is platinum, which may be alloyed with other noble or base metals. Base metals are non-noble tin or transition metals. Noble metals are platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, or osmium), gold, or silver. Suitable base metals include copper, cobalt, nickel, zinc, iron, titanium, molybdenum, vanadium, manganese, niobium, tantalum, chromium, and tin. Preferred base metals are nickel, cobalt, and chromium. More preferred base metals are nickel and cobalt.

[0031] Preferably, the electrocatalyst comprises platinum, palladium, rhodium, ruthenium, iridium, and / or osmium.

[0032] The electrocatalyst may be a reduced monometallic electrocatalyst, such as a Pt catalyst.

[0033] The electrocatalyst may comprise an alloy, such as a binary alloy. In particular, the alloy may comprise a Pt a X b wherein the ratio of a to b is in the range of 10:1 to 1:2.5, optionally 5:1 to 1:2.5, inclusive, and X is Co, Ni, Y, Gd, Sc, or Cu. Preferably, X is Co or Ni, most preferably Ni.

[0034] The exact electrocatalyst used will depend on the reaction it is intended to catalyze, and its selection is within the ability of one skilled in the art.

[0035] The amount of electrocatalyst (eg, electrocatalyst particles) supported on the carbon support is suitably 10 to 90 wt %, for example 15 to 75 wt %, preferably 20 to 60 wt %, of the weight of the resulting supported electrocatalyst.

[0036] Carbon Support The carbon support is typically a particulate carbon support.

[0037] Suitable carbons typically include those from the carbon black family, such as oil furnace black, polar conductive black, acetylene black, and graphitized versions thereof. Exemplary carbons include Ketjenblack™ EC-300J and Cabot Vulcan® XC72R. Additionally, carbons specifically designed for fuel cell applications, such as those described in WO 2013 / 012894, can be used.

[0038] The carbon support is preferably particulate carbon black, the surface of which is optionally graphitized.

[0039] Nitrogen-functionalized carbon supports N-functionalized carbon supports are sometimes referred to as N-doped carbon supports. N-functionalization involves incorporating N atoms into the carbon support and includes many different N species, as described by Jansen et al. (RJJ Chem. Soc. Jansen and van Bekkum, Carbon, 32, 1507 (1994)) and Ott et al. (Nat. Mater. 19, 77-85 (2020)).

[0040] N-functionalized carbon supports can include graphitic N species, quaternary N species, pyrrolic N species, and / or pyridine N species. Graphitic N species correspond to graphite with neutral N atoms in place of carbon atoms in the six-membered ring. Quaternary N species are positively charged, and an example is shown in Figure 2 (dashed diamond).

[0041] Pyrrole N species are based on pyrrole CHNH, examples of which are shown in Figure 2 (dashed circle). Pyridine N species are based on pyridine CHN, examples of which are shown in Figure 2 (dashed square).

[0042] The N-functionalized carbon support may comprise a carbon lattice comprising carbon and nitrogen atoms, and optionally hydrogen and / or oxygen atoms. Preferably, the carbon lattice comprises pyridine and / or pyrrole units.

[0043] 2 also shows nitroso-N species (-N=O), which may be present in small amounts. The N-functionalized carbon support may contain surface N in an amount of ≦2.0 wt. %, preferably ≦1.0 wt. %, and preferably ≦0.8 wt. %, as determined by XPS. The N-functionalized carbon support may contain surface N in an amount of at least 0.1 wt. %, preferably at least 0.3 wt. %, as determined by XPS. The N-functionalized carbon support may contain surface N in an amount within a range including any combination of the above upper and lower limits.

[0044] Catalyst ink and catalyst layer The method may include the further step of incorporating the supported catalyst of the present invention into a catalyst layer. The supported catalyst may be formulated into an ink. The ink may include the supported catalyst, an ionomer, and a dispersant.

[0045] The ink can be deposited to form a wet catalyst layer, which can then be dried (to remove the dispersant) and annealed to form the catalyst layer. The ink can be deposited (i) onto a decal transfer substrate, (ii) onto an ion-conducting (e.g., electrolyte) membrane, i.e., directly, or (iii) onto another catalyst layer.

[0046] The ratio of ionomer to N-functionalized carbon support (in the ink or catalyst layer) may be from 0.1 to 2.0, optionally from 0.2 to 1.0 or from 0.5 to 1.5.

[0047] The N-functionalized carbon support may constitute 20 to 80 wt %, optionally 35 to 55 wt %, of the catalyst layer.

[0048] Ionomer Ionomers are ion-conducting polymers, such as proton-conducting polymers or anion-conducting polymers (e.g., hydroxyl anion-conducting polymers). The ionomer is preferably a proton-conducting polymer. Examples of suitable proton-conducting polymers include perfluorosulfonic acid ionomers (e.g., Nafion® (EI DuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion™ (Solvay Specialty Polymers), Flemion® (Asahi Glass Co.), or ionomers based on sulfonated hydrocarbons, such as those available from FuMA-Tech GmbH as fumapem® P, E, or K series products, JSR Corporation, Toyobo Corporation, etc. Examples of suitable anion-conducting polymers include A901 from Tokuyama Corporation and Fumasep FAA from FuMA-Tech GmbH.

[0049] electrolyte membrane The electrolyte membrane includes an ion-conducting polymer. The ion-conducting polymer is preferably a proton-conducting polymer. A preferred ion-conducting polymer is a partially or fully fluorinated sulfonic acid polymer, such as a perfluorosulfonic acid polymer. For example, the ion-conducting polymer may be based on perfluorosulfonic acid materials such as Nafion® (Chemours Company), Aquivion® (Solvay Specialty Polymers), Flemion® (Asahi Glass Group), and Aciplex® (Asahi Kasei Chemicals Corp.). Alternatively, the ion-conducting material may be based on sulfonated hydrocarbon polymers such as those available as fumapem® P, E, or K series products from FuMA-Tech GmbH, JSR Corporation, Toyobo, and other companies.

[0050] Catalyst coated membrane (CCM) The present invention also relates to CCM obtainable or obtained by the method of the present invention.

[0051] The CCM includes an electrolyte membrane and a catalyst layer, the electrolyte membrane having a first surface and an opposing second surface, and the catalyst layer located on the first surface.

[0052] The catalyst layer may contain crack defects covering an area of ​​less than 8% of the total area of ​​the catalyst layer when measured after applying a 30% strain to the catalyst coated membrane. [Brief explanation of the drawings]

[0053] [Figure 1] 1A is a schematic diagram for comparing the method of the present invention (FIG. 1A) with the prior art method (FIG. 1B). [Figure 2] Examples of types of N-functionalization are shown below. [Figure 3]1 shows XPS signals for 50%Pt / N-EC300j, an N-functionalized catalyst prepared using N-EC300j according to known methods; 50%Pt / PostN-EC300j, an N-functionalized catalyst prepared by post-functionalization of 50%Pt / EC300j; and 50%Pt / PostN-EC300j AT, an N-functionalized catalyst prepared by acid modification of 50%Pt / PostN-EC300j. [Example]

[0054] 1. Carbon activation with nitric acid A quantity of 120 g or less of the desired carbon black material (EC300j Ketjen Black carbon) was transferred to a glass reactor with a 20 L or less vessel preheated to 75°C. 42 mL of 70% nitric acid per gram of carbon support was slowly added. The mixture was stirred at 75°C under reflux conditions using a condenser for 1 hour. After the reaction time, the mixture was allowed to cool to room temperature, filtered, washed with deionized water, and dried in a vacuum oven. The resulting material is referred to as activated carbon (O-EC300j). Activated carbons produced by this method have higher levels of O and lower levels of NO on their surface, as confirmed by XPS. - This type of N is unstable and easily removed. See the table below for N amounts.

[0055] 2. NH3 treatment of activated carbon A quantity of 40 g or less of activated carbon (produced in 1.) was placed in a tube furnace. The furnace was then purged with Ar overnight. After purging, the material was placed under a 100% NH3 flow at 360 mL / min and heated to 600 °C at 10 °C / min, followed by a 5-hour dwell. After treatment, the material was cooled to room temperature. The flow was switched back to Ar below 200 °C and allowed to cool. The resulting material, designated N-functionalized carbon (N-EC300j), contains a mixture of pyridine and pyrrolic N species on the surface as confirmed by XPS. See the table below for the amount of N.

[0056] 3. NH3 treatment of fresh carbon A quantity of 40 g or less of EC300j Ketjen Black carbon was placed in a tube furnace. The furnace was then purged with Ar overnight. After purging, the material was placed under a 100% NH3 flow at 360 mL / min and heated to 600 °C at 10 °C / min, followed by a 5-hour dwell. After treatment, the material was cooled to room temperature. The flow was switched back to Ar below 200 °C and allowed to cool. The resulting material does not exhibit N functional groups on its surface. N cannot be detected by XPS or CHN techniques.

[0057] 4. Synthesis of 50% Pt EC300j Pt was deposited onto the material as described in WO2013045894A1 using EC300j Ketjenblack carbon as the carbon support.

[0058] The carbon support material was dispersed in water using a shear mixer. The slurry was transferred to a beaker equipped with temperature and pH probes and two feed inlet tubes connected to a pH control unit. Pt salt (Pt nitrate or KPtCl) was added in an amount sufficient to provide a nominal Pt loading of 50 wt%. NaOH was added to maintain the pH between 5.0 and 7.0 (final pH). The slurry was stirred, and once hydrolysis was complete, formaldehyde was added to reduce the Pt. Upon reaction completion, the catalyst was recovered by filtration and washed on the filter bed. N was not detectable by XPS.

[0059] 5. Synthesis of 50% Pt / N-EC300j Pt was deposited onto the material as described in WO2013045894A1 using EC300j (N-functionalized carbon black from 2.) as the carbon support.

[0060] The N-functionalized carbon support material (from 2.) was dispersed in water using a shear mixer. The slurry was transferred to a beaker equipped with temperature and pH probes and two feed inlet tubes connected to a pH control unit. Pt salt (Pt nitrate or KPtCl) was added in an amount sufficient to give a nominal Pt loading of 50 wt. NaOH was added to maintain the pH between 5.0 and 7.0 (final pH). The slurry was stirred, and once hydrolysis was complete, formaldehyde was added to reduce the Pt. Upon reaction completion, the catalyst was recovered by filtration and washed on a filter bed.

[0061] This material maintains the N-functionalization of the support and the same type of N. The amount of N is reduced to half of what would be expected for a 50 wt. % Pt catalyst with a functionalized support. See the table below for the amount of N.

[0062] 6. Example 1, Synthesis of 50% Pt / PostN-EC300j A quantity of 50% Pt / EC300j catalyst up to 40 g was placed in a tube furnace. The furnace was then purged with Ar overnight. After purging, the material was placed under a 100% NH3 flow at 360 mL / min and heated to 600 °C at 10 °C / min, followed by a 5-hour dwell. After treatment, the material was cooled to room temperature. The flow was switched back to Ar below 200 °C and allowed to cool. Once at temperature, the flow was changed to N2, and a small amount of air was added continuously before exposing the material to the atmosphere.

[0063] This material, called 50%Pt / PostN-EC300j, presents the same amount of N as 50%Pt / N-EC300j but with more reduced N species, which can be modified by acid treatment.

[0064] 7. Example 2, Acid Modification of N Species A quantity of 100 g of the desired 50% Pt / PostN-EC300j (from 6) was transferred to a glass reactor with a capacity of 5 L or less. 80 mL of 0.5 M H2SO4 solution per gram of catalyst was slowly added. The mixture was stirred at 80 °C under reflux conditions using a condenser for 24 hours. After the reaction time, the mixture was allowed to cool to room temperature, filtered, washed with deionized water, and dried in a vacuum oven.

[0065] This material, designated 50%Pt / PostN-EC300j AT, presents the same amount of N as 50%Pt / PostN-EC300j, but presents more oxidized N species, comparable to 50%Pt / N-EC300j.

[0066] overview [Table 1]

[0067] result XPS (X-ray Photoelectron Spectroscopy) is a surface-specific elemental analysis technique that involves bombarding a sample with X-rays of sufficient energy to eject electrons from the atoms that make up the sample in an ultra-high vacuum environment. Ultra-high vacuum conditions are necessary for two reasons: (i) to allow the emitted electrons to reach the detector without losing energy through collisions, and (ii) to keep the surface free of absorbed species. The emitted electrons are measured for their kinetic energy, from which their binding energy can be calculated according to the following formula: E K =hv-E B -f

[0068] In the formula, E K is the kinetic energy, hv is the energy of the radiation, and E B is the binding energy and f is the work function of the spectrometer.

[0069] The binding energy can then be correlated to the element of origin, including not only the element but also the electron shell (s, p, d, f) from which the electron originates. Electrons are also counted, and the intensity can be used to provide a quantitative analysis of the detected elements. A scan over a range of binding energies, typically 0-1100 eV, provides a spectrum representing intensity as a function of binding energy that can be processed to identify and quantify the detected elements. The binding energy of a particular element can also indicate the oxidation state of that element. In some cases, such as with sulfur, this is readily apparent from a broad scan, but in most cases, a high-resolution scan over a narrow binding energy range must be performed. This results in a spectral envelope that can be resolved into individual components.

[0070] X-ray photoelectron spectroscopy (XPS) data were collected using a Thermo Scientific NEXSA at a base pressure of 5E-10 mbar. Radiation was generated using a monochromated aluminum Kα source with an elliptical spot size of 400 × 800 μm. A dual-mode (electron and argon ion) flood gun was used for charge compensation. Modified Schofield sensitivity factors were used during quantification using Avantage software. Samples were prepared using a powder holder plate consisting of a well containing the powder. Carbon tape was not used in these studies.

[0071] Surface weight percent of C, O, N, and Pt by XPS

[0072] [Table 2]

[0073] Referring to the table above, it can be seen that 50%Pt / PostN-EC300j (N-functionalized after catalysis) achieves the same N content (0.6%) as 50%Pt / N-EC300j (N-functionalized before catalysis). Acid treatment (50%Pt / PostN-EC300j AT) is used to modify the N to O ratio as desired.

[0074] Figure 3 compares the XPS signals for 50%Pt / N-EC300j, 50%Pt / PostN-EC300j (Example 1), and 50%Pt / PostN-EC300j AT (Example 2), revealing different types of N-functionalization, namely, pyridine (A), pyrrolic (B), quaternary (C), graphitic (D), NO2 - (E), and NO3 - (F) shows that pyridine (A) and pyrrole (B) are predominant.

Claims

1. 1. A method for preparing a supported catalyst comprising an electrocatalyst on a nitrogen-functionalized carbon support, comprising: (i) providing an electrocatalyst on a carbon support; (ii) incorporating nitrogen into the carbon support to provide the supported catalyst, wherein the supported catalyst comprises an electrocatalyst on a nitrogen-functionalized carbon support.

2. The method of claim 1 , wherein incorporating nitrogen into the carbon support comprises exposing the carbon support to gaseous ammonia.

3. 3. The method of claim 2, wherein the carbon support is exposed to ammonia at a temperature of 200°C or more and / or 1100°C or less.

4. The method of claim 3, wherein the carbon support is exposed to ammonia at a temperature of from 500 to 1000°C, optionally from 500 to 800°C.

5. A method according to any one of claims 1 to 4, comprising an initial step of catalysing carbon to obtain said electrocatalyst on said carbon support.

6. The method of any one of claims 1 to 5, comprising a subsequent acid treatment step to modify the N-functionalized carbon support.

7. The method of any one of claims 1 to 6, wherein the electrocatalyst comprises electrocatalyst particles on a particulate carbon support.

8. The method of any one of claims 1 to 7, wherein the electrocatalyst comprises platinum, palladium, rhodium, ruthenium, iridium, and / or osmium.

9. The electrode catalyst is Pt ａ X ｂ 9. The method of claim 8, comprising: wherein the ratio of a to b is in the range of and including 10:1 to 1:2.5, optionally 5:1 to 1:2.5, and X is Co, Ni, Y, Gd, Sc, or Cu.

10. The method of any one of claims 1 to 9, wherein the electrocatalyst comprises 10 to 90 wt% of the resulting supported electrocatalyst.

11. A supported catalyst produced or producible by the method of any one of claims 1 to 10, comprising an electrocatalyst on an N-functionalized carbon support.

12. A catalyst layer comprising the supported catalyst of claim 11 and optionally an ionomer.

13. A catalyst coated membrane comprising the catalyst layer of claim 12 disposed on an electrode membrane.

14. A gas diffusion electrode comprising the catalyst layer of claim 12 disposed on a gas diffusion layer.

15. A decal comprising the catalyst layer of claim 12 disposed on a decal transfer substrate.

16. A membrane electrode assembly comprising the catalyst layer of claim 12, the catalyst coated membrane of claim 13, or the gas diffusion electrode of claim 14.

17. 17. An electrochemical device, such as a fuel cell or an electrolyzer, comprising the membrane electrode assembly of claim 16.

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