Porous catalyst layers made of low-dispersion porous spherical carbon particles and metal nanoparticles supported thereon, membrane electrode assemblies made therefrom, and their applications.

Abstract

This invention relates to porous catalyst layers comprising porous carbon structures supported on metal nanoparticles, wherein the porous carbon structures are assembled from porous spherical carbon particles having a particle size distribution (Ð) of 1.2 or less and having templated pore sizes having a templated pore size distribution (Ð') of 1.2 or less. The invention also relates to methods for producing such porous catalyst layers, electrodes obtained from such porous catalyst layers, and their use in fuel cells or electrolyzers.

Description

Technical Field

[0001] This invention relates to porous catalyst layers loaded with metal nanoparticles for use in membrane electrode assemblies, methods for their production, and their use in membrane electrode assemblies. The invention also relates to proton or anion exchange membrane fuel cells and electrolyzers utilizing the porous catalyst layers according to the invention. Background Technology

[0002] Membrane electrode assemblies (MEAs) play a central role in electrochemical energy conversion, including proton exchange membrane (PEM) and anion exchange membrane (AEM) fuel cells and electrolyzers. They form the electrochemical core of these technologies and determine the performance metrics achieved, such as power density or hydrogen production rate. An MEA consists of several tightly connected components: an anode gas diffusion layer (GDL), an anode catalyst layer (ACL), a PEM or AEM, a cathode catalyst layer (CCL), and a cathode GDL. The GDL may also include a microporous layer (MPL).

[0003] MEAs can be processed and assembled in two ways. On one hand, PEM or AEM can be coated with an anode catalyst on one side to obtain an ACL. The other side is coated with a cathode catalyst to obtain a CCL. The tightly bonded layer structure between the ACL, PEM, or AEM and the CCL is called a catalyst-coated membrane (CCM). Then, microporous layers and gas diffusion layers are provided on both sides of the CCM and pressed together. Different methods are based on coating the anode and cathode sides with microporous layers and gas diffusion layers using an anode catalyst layer (ACL) and a cathode catalyst layer (CCL) to obtain an anode gas diffusion electrode and a cathode gas diffusion electrode. To assemble the MEAs, they are then pressed together with PEM or AEM. The three-dimensional structure of the catalyst layer (percolation, tortuosity, porosity, ionomer to carbon content ratio) is a crucial factor in the final performance of PEM / AEM-based electrochemical energy conversion systems (i.e., hydrogen PEM / AEM fuel cells or PEM / AEM water electrolyzers).

[0004] The catalyst layer (ACL and CCL) comprises constituent particles (typically carbon particles) bound together by an ionically conductive polymer (so-called ionomer), which acts as an electrolyte and binder within the catalyst layer and between the catalyst layer and the membrane. The constituent particles are loaded with a catalytic substance that imparts catalytic activity, thereby forming catalyst particles that, after assembly, can subsequently produce the catalyst layer. The catalyst layer can be produced, for example, using various coating techniques from an ink or paste containing a solvent, ionomer, and corresponding constituent particles. This produces a porous catalyst layer or electrode, where the porosity is determined, for example, by the interparticle packing of the constituent particles and the aggregation behavior of these particles.

[0005] In their review article "Engineering Catalyst Layers for Next-Generation Polymer Electrolyte Fuel Cells: A Review of Design, Materials, and Methods" (Adv. Energy Matter. 2021, 11, 2101025; https: / / doi.org / 10.1002 / aenm.202101025), Suter et al. demonstrated that the degree of interparticle porosity (i.e., the porosity between constituent particles) in the catalyst layer is determined by the morphology of the constituent particles themselves (primary particles) and their secondary aggregates, and is significantly influenced by the morphology of the carbon support, ionomers, the composition of the catalyst ink or paste, and the coating process. A similar relationship was described by Liu et al. in their review article “Effect of Catalyst Ink and Formation Process on the Multiscale Structure of CatalystLayers in PEM Fuel Cells” (Appl. Sci. 2022, 12, 3776; https: / / www.mdpi.com / 2076-3417 / 12 / 8 / 3776).

[0006] The optimized porous structure of the catalyst layer addresses the following requirements: high interparticle conductivity through the contact packing of constituent particles; rapid ion transport through the continuous percolation of ionomers around the constituent particles and into the membrane; and rapid gas and water transport through the highly porous morphology of the catalyst particle / ionomer aggregates. The most important structural determinant of the three-dimensional porous catalyst layer is the (carbon) support, which determines the morphology of the catalyst particles and contains the catalytically active material (e.g., Pt nanoparticles in fuel cells and electrolysis technologies).

[0007] Existing catalysts for PEM / AEM fuel cell anodes and cathodes, as well as PEM / AEM electrolyzer cathodes, consist of metal nanoparticles finely distributed on the surface or in the pores of conductive carbon supports (carbon black) such as Black Pearls (R), Vulcan (R), and Ketjenblack (R) (see, for example, Wang et al., “Achievements, challenges and perspectives on cathode catalysts in proton exchange membrane fuel cells for transportation” (Nature Catalysis 2019, 2, 578-589; https: / / doi.org / 10.1038 / s41929-019-0304-9)).

[0008] All these carbon supports exhibit highly dispersed primary particle sizes (<100 nm), which aggregate into larger, indeterminate porous secondary particles. The porosity and 3D porous structure of the catalyst layer in a CCM or gas diffusion electrode (GDE) depend significantly on the following parameters: constituent particle size, constituent particle size distribution, constituent particle morphology, and the agglomeration of constituent particles and the stability of potential agglomerates in the dispersion medium, i.e., single-particle dispersibility. These factors determine the percolation and stacking of constituent particles that produce the catalyst layer, which in this case defines the interparticle porosity within the layer. Intraparticle porosity (if present) defines the additional porosity and hierarchical level within the catalyst layer and determines the location of the catalytically active metal nanoparticles; located outside the constituent particles in the case of non-porous primary particles, and inside the constituent particles in the case of highly porous primary particles.

[0009] The porosity levels between and within particles are essential for optimizing the mass transport of reactants and products in the catalyst bed, and thus affect the system's performance and lifespan.

[0010] As previously mentioned, prior art metal nanoparticle-based catalysts for PEM / AEM fuel cell anodes and cathodes, as well as PEM / AEM electrolyzer cathodes, are based on highly dispersed carbon supports with a wide particle size distribution, thus inherently possessing a very broad compositional particle size distribution. This results in catalyst layers based on these having uncontrolled porosity, which is therefore poorly reproducible and cannot be tuned to maximum performance because the support carbon has a highly dispersed particle size due to its manufacturing process. Therefore, based on currently available prior art catalysts, it is impossible to achieve controlled or customized bottom-up 3D catalyst layer / electrode designs because prior art catalysts consist of highly dispersed, untunable carbon materials; this is independent of the catalytically active metal nanoparticles supported on these carbons.

[0011] When manufacturing catalysts composed of these carbons or integrating them into CCM, GDE, or MEA, an indeterminate porous catalyst layer is produced, where the porosity is determined by the packing of constituent particles or secondary catalyst aggregates. Due to the high dispersion of the constituent particles, the 3D porous structure of the catalyst layer is not adjustable, has poor reproducibility, and in many cases (if the electrode thickness is too high), only partial entry of gases, protons, hydroxide anions, etc., is possible. Furthermore, mass transport within the catalyst layer is difficult to optimize because the porosity is predetermined by the morphology and size of the processed constituent particles, severely limiting the performance of this unoptimized CCM / GDE / MEA, especially at high current densities. Finally, if the constituent particles are very small, their tight packing during catalyst layer formation results in low interparticle porosity, further limiting the entry of gases, protons, hydroxide anions, etc. This limits the achievable power of PEM / AEM fuel cells and the achievable hydrogen production rates of PEM / AEM electrolyzers.

[0012] Joo et al. disclosed a Pt-supported mesoporous carbon catalyst in “Preparation of mesoporous carbon templated by silicaparticles for use as a catalyst support in polymer electrolyte membrane fuel cells” (Catalysis Today 111 (2006), 171-175). However, as shown by TEM imaging, this catalyst exhibits an irregular morphology.

[0013] Shu et al. disclosed the formation of iron-loaded mesoporous carbon spheres in “Hierarchically mesoporous carbon spheres coated with a single atomic Fe-NC layer for balancing activity and mass transfer in fuel cells” (Carbon Energy. 4 (2022) 1-11), which consist of hierarchically porous carbon spheres (HPCS) as the core and a single Fe-atom-doped m-phenylenediamine coating (Fe-mPDA) as the functional shell. However, these structures have a large particle size dispersion, making it impossible to produce catalyst layers with regular structures.

[0014] EP 3 828 133 A1 discloses the use of mesoporous carbon as a catalyst support for the air electrode catalyst support in polymer electrolyte fuel cells. In this case, as shown by SEM imaging, the structure of the mesoporous carbon is also irregular, and the obtained electrode structure is not reproducible.

[0015] Choi et al. disclosed in “Single-Step Fabrication of a Multiscale Porous Catalyst Layer by the Emulsion Template Method for Low Pt-Loaded Proton ExchangeMembrane Fuel Cells” (ACS Appl. Energy Mater. 2021, 4, 4, 4012 - 4020) a method for single-step fabrication of a multiscale porous catalyst layer with macropores and mesopores using an emulsion template method.

[0016] Wang et al. disclosed composite particles obtained by oxidative polymerization of aniline in the presence of a silica template in “Controlled Synthesis of N-Doped Carbon Nanospheres with Tailored Mesopores through Self-Assembly of Colloidal Silica” (Angew. Chem. Int. Ed. 2015, 54, 15191 - 15196). However, the obtained particle size and pore size could not be independently controlled, and the obtained particle size distribution was unsatisfactory.

[0017] Therefore, existing technologies pose a problem. Summary of the Invention

[0018] The present invention is defined in the appended claims.

[0019] The solution to the described problem according to the present invention starts with low-dispersion porous spherical carbon particles with adjustable pore size and particle size, and employs low-dispersion porous carbon particles loaded with metal nanoparticles (with adjustable pore size and particle size). This allows for the fabrication of a three-dimensional (3D) percolation porous catalyst layer based on it, with adjustable interparticle and intraparticle porosity.

[0020] Specifically, the present invention is embodied in a porous catalyst layer comprising a porous carbon structure supported on metal nanoparticles. The porous carbon structure is assembled from porous spherical carbon particles having a particle size dispersion Ð of 1.2 or less and a templated pore size having a templated pore size dispersion Ð' of 1.2 or less. In a preferred embodiment, the particle size dispersion Ð and / or the templated pore size dispersion Ð' of the porous spherical carbon particles used to assemble the porous catalyst of the present invention may be 1.1 or less.

[0021] Therefore, the structure and morphology of porous catalyst layers can be controlled by adjusting the shape and size of carbon particles, their intraparticle porosity, and the 3D interparticle porosity between carbon particles loaded with metal nanoparticles in the catalyst layer. The particle size distribution of the carbon structure within the catalyst corresponds to the particle size distribution of the spherical carbon support particles. The intraparticle porosity of the carbon particles within the catalyst layer also corresponds to the intraparticle porosity of the carbon support particles. This results in a highly defined hierarchical 3D porous catalyst layer with adjustable porosity. Although the presence of metal nanoparticle loading within the porous catalyst layer structure may affect the actual porosity of the structure, this variation in porosity does not significantly affect its properties. Therefore, the mass transport properties of the catalyst layer can be specifically controlled via the properties of the carbon support and the catalyst derived from it, thereby producing improved performance values ​​in PEM / AEM fuel cells and PEM / AEM electrolyzers.

[0022] Therefore, this method systematically achieves reproducibility optimization, porosity adjustment, and improved mass transport in CCM, GDE, or MEA. Optimized mass transport enables higher current densities, i.e., higher power densities or hydrogen production rates, in PEM / AEM fuel cells and PEM / AEM electrolyzers.

[0023] According to one embodiment of the invention, the porous spherical carbon particles may have a particle size of 10 nm to 5000 nm, preferably 25 nm to 2500 nm or 50 nm to 500 nm, and wherein the templated pore size is 1 nm to 1000 nm, preferably 2 nm to 500 nm or 5 nm to 100 nm. Using these particle sizes and templated pore sizes can produce a specific surface area of ​​25 m². 2 g -1 up to 3000m 2 g -1 or 200m 2 g -1 up to 1500m 2 g -1 The pore volume is 0.1 cm³. 3 g -1 up to 5.0cm 3 g -1 or 0.25cm 3 g -1 up to 3.0cm 3 g -1 The porous carbon structure.

[0024] According to one embodiment of the invention, the porous carbon structure may have a metal nanoparticle loading of 1 wt% to 95 wt% based on the total weight of the porous carbon structure loaded with metal nanoparticles. For example, the loading may be 5 wt% to 90 wt%, or 10 wt% to 85 wt%, or 15 wt% to 80 wt%, or 20 wt% to 75 wt%, or 25 wt% to 70 wt%, or 30 wt% to 65 wt%, or 35 wt% to 60 wt%, or 40 wt% to 55 wt%, or 45 wt% to 50 wt%. Depending on the intended use, the catalytic activity of the porous catalyst layer according to the invention can be adjusted according to the metal nanoparticle loading.

[0025] According to one embodiment of the invention, the metal nanoparticles may be selected from nanoparticles made of a single metal or metalloid element (including transition metals) or an alloy containing different metals and / or metalloid elements. For example, the metal nanoparticles may be metals from Groups 1, 2, 12, 13, 14, 15, or 16 of the periodic table, or any transition metal from Groups 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 of the periodic table, or any metal from the lanthanides or actinides, or any metalloid nanoparticles from Groups 13, 14, 15, 16, or 17 of the periodic table. Alternatively, the metal nanoparticles may be alloys of any two or more metals and / or metalloid elements from the groups indicated above. According to the invention, the metal nanoparticles supported on the porous carbon structure may have the same or different metal compositions.

[0026] According to one embodiment of the present invention, the diameter of the metal nanoparticles in the porous catalyst layer in any dimension may not exceed 100 nm, for example, 1 nm to 75 nm, or 2 nm to 60 nm, or 3 nm to 40 nm, or 4 nm to 25 nm, or 5 nm to 20 nm, or 7 nm to 15 nm, or 8 nm to 10 nm.

[0027] According to one embodiment of the invention, the interparticle pore volume of the porous carbon structure can be 15% to 60%, for example 20% to 55%, or 25% to 50%, or preferably 26% to 48%. Interparticle pore volume refers to the volume of the porous carbon structure that leaves voids between the individual porous spherical carbon particles after assembly. The interparticle pore volume can be selected to achieve the best possible results depending on the intended use of the porous carbon structure. The interparticle pore volume is based on calculated estimates, assuming low particle size distribution (ε ≤ 1.2) and the closest packing configurations of cubic close packing or hexagonal close packing as one extreme, and simple cubic packing as another extreme, where higher particle size distribution may result in lower interparticle pore volume, and gaps in the packing may result in higher interparticle pore volume.

[0028] According to one embodiment of the invention, the ratio of intraparticle pore volume to interparticle pore volume can be from 0.05 to 3.0, preferably from 0.1 to 2.0, and more preferably from 0.7 to 1.9. The intraparticle pore volume is derived from the volume of the templated pores of the porous spherical carbon particles used to assemble the porous carbon structure according to the invention, while the interparticle volume refers to the volume of the porous carbon structure leaving voids between the individual porous spherical carbon particles after assembly. The intraparticle pore volume is measured on the free porous spherical carbon particles before layer formation, as the cumulative pore volume calculated by QSDFT from N2 physisorption. Assuming a perfect packing fill rate of 74% for the spherical carbon particles, the ratio of intraparticle pore volume to interparticle pore volume is derived from the density measurement of the porous carbon structure (obtained by hydrometry). The ratio of intraparticle pore volume to interparticle pore volume can be selected to achieve the best possible results depending on the intended use of the porous carbon structure.

[0029] Another part of the invention is a porous carbon structure comprising two or more porous catalyst layers of the invention, wherein the two or more porous catalyst layers are arranged in a layered manner. In this case, the individual porous catalyst layers may have the same or different particle sizes. Alternatively or supplementarily, the individual porous catalyst layers may have the same or different templated pore sizes.

[0030] Another part of the present invention is a method for producing the porous catalyst layer of the present invention. The method includes the following steps: (i) providing low-dispersion porous spherical carbon particles loaded with metal nanoparticles as described above; (ii) mixing the provided porous spherical carbon particles loaded with metal nanoparticles with one or more additives (particularly a polymeric electrolyte); (iii) applying the obtained mixture onto a substrate to form a porous carbon structure layer loaded with metal nanoparticles; (iv) drying and / or curing the applied mixture to form a dried layer of the porous carbon structure loaded with metal nanoparticles; and (v) optionally calendering the dried layer of the porous carbon structure loaded with metal nanoparticles. The porous carbon structure of the present invention can be obtained by forming a plurality of porous catalyst layers on top of each other.

[0031] According to one embodiment of the invention, the mixing step (ii) includes adding a dispersion medium to form an ink or paste, and the step (iii) is performed by 3D printing, slot coating, inkjet printing, blade coating, spray coating, spin coating, or dip coating.

[0032] Another part of the present invention is a membrane electrode assembly comprising one or more catalyst layers, the one or more catalyst layers being composed of or containing a porous carbon structure supported on metal nanoparticles according to the present invention.

[0033] According to one embodiment of the invention, the catalyst layer of the membrane electrode assembly may further comprise one or more binders, such as polymer binders and / or ionomers.

[0034] Finally, the present invention also covers the use of porous catalyst layers or membrane electrode assemblies according to the present invention in electrochemical energy conversion devices such as PEM / AEM fuel cells or PEM / AEM electrolyzers. Attached Figure Description

[0035] The invention will be further illustrated with reference to the following figures: Figure 1 This is a schematic diagram of the MEA layered structure; Figure 2 This is a schematic diagram comparing the high dispersion particle size of the prior art (left) that leads to an undefined electrode structure with the low dispersion particle size (right) that can produce a defined and reproducible porous catalyst layer according to the present invention; Figure 3 SEM images of prior art (a, b, c) and carbon support materials according to the present invention (e, f, g) in SE (secondary electron) mode are shown, with the corresponding particle size distributions (d, h) shown. Figure 4 Results of prior art and the present invention, on a 3P instrument machine, for nitrogen physisorption measurements at 77 K are shown, including (a) isotherms, (b) pore size distribution calculated via a QSDFT model, and (c) BET surface areas of Ketjenblack and MPNC-7-130, respectively, at 785 m². 2 g -1 and 876m 2 g -1 ; Figure 5 XRD (b) on a Bruker D8 Discover device according to the prior art and the present invention, and SEM images of the prior art (c, d, g, h) and the present invention (a, e, f, I, j) in SE (secondary electron) mode and TE (transmission electron) mode are shown. Figure 6 SEM images of coatings prepared from inks based on electrocatalyst materials according to the prior art (a, c, e) and the present invention (b, d, f) are shown. Figure 7 Polarization curves (a), mass activity (b), electrochemical surface area (ECSA) (c), and peak power density (d) of the prior art and the present invention are shown.

[0036] It should be understood that the following description and reference to the accompanying drawings relate to exemplary embodiments of the invention and should not limit the scope of the claims. Detailed Implementation

[0037] To better understand this invention, the following interpretations of the terms used herein are considered useful. In the context of this invention, the following definitions apply: As used in this application, "porous catalyst layer" refers to a percolation structure suitable for catalyst-coated membranes. For example, a porous catalyst layer may include a supported metal catalyst for improving reaction rate and electron conduction, ionomers for ion conduction, and pores for transport of reactant gases and water.

[0038] As used herein, "porous carbon structure" refers to a structure comprising a solid stable assembly of percolated carbon particles, wherein individually assembled carbon particles are specifically arranged in space relative to each other, and wherein the voids between the individual carbon particles form interparticle porosity. As used herein, porous carbon structures may include additional materials in addition to percolated carbon particles, such as heteroatoms, dopants, additives, binders, and other substances.

[0039] "Particle size," also known as grain size, refers to the spatial range of a single particle. Particle size is determined by counting the diameters of a sufficiently large number of particles (at least 200 particles) in an electron micrograph obtained by scanning (transmission) electron microscopy. Non-spherical particles (such as elliptical particles) are described by their minimum and maximum diameters.

[0040] Particle size dispersion (D-stroke) is based on the IUPAC definition of dispersion given in Pure Appl. Chem. (Vol. 83, No. 12, pp. 2251-2259, 2011). Particle size dispersion The width of the particle size distribution is measured and determined by... Given, among which N i Indicates having a diameter d i The number of particles. For a sample with completely uniform particle size, The value will be 1. Narrow particle size distributions with a value ≤1.2, preferably ≤1.1, can be referred to as monodisperse particles or low-dispersion particles. Particle size distributions with a value >1.2 can be referred to as polydisperse particles or highly dispersed particles.

[0041] "Aperture" (pore width) refers to the distance between the two opposite walls of a pore. According to the IUPAC nomenclature (Pure & Appl. Chem. Vol. 66, No. 8, pp. 1739-1758, 1994), micropores have a width of less than 2 nm, mesopores have a width between 2 nm and 50 nm, and macropores have a width greater than 50 nm.

[0042] "Templated pore size" refers to the diameter of the spherical template used to form pores in the spherical porous carbon particles used in this invention. The particle size can be determined by counting the particle sizes of a sufficiently large number of particles (at least 200 particles) on an electron micrograph obtained by scanning (transmission) electron microscopy. The polymerization of the carbon precursor in the presence of a nanoscale spherical template results in the formation of a carbon-template composition. Removal of the template material leaves nanoscale pores within the polymeric carbon structure. The pores can be interconnected, and therefore the pores will not simply have a spherical shape, but rather they can take the shape of juxtaposed spheres with different cross-sectional diameters. Therefore, "templated pore size" can differ from the measured pore size, and the templated pore size dispersion can differ from the measured pore size dispersion. Templated pore size dispersion 'Corresponds to the particle size distribution of the template used to form pores.'

[0043] "Nanoparticles" refers to particles of any shape with a size ranging from 1 nm to 100 nm. Only tubes and fibers with two dimensions less than 100 nm are also nanoparticles (see Pure Appl. Chem., 84, 2, 377-410).

[0044] The present invention, according to the appended claims, provides low-dispersion porous carbon particles with adjustable particle size and pore size supported on metal nanoparticles for constructing a 3D percolation catalyst layer thereon, wherein the interparticle porosity is defined by the arrangement of the low-dispersion spherical carbon particles supported on metal nanoparticles, and the intraparticle porosity is defined by the intraparticle porosity of the low-dispersion spherical carbon particles supported on metal nanoparticles.

[0045] Prior to the conception of this invention, such methods did not exist in the production of MEAs, CCMs, or GDEs for fuel cells and electrolyzers because there were virtually no readily available large-scale, commercially viable low-dispersion porous carbon particles loaded with metal nanoparticles, wherein the carbon particle size and pore size could be tuned to construct the catalyst layer according to the invention. Therefore, it was impossible to construct a controllable hierarchical 3D porosity in the catalyst layer using existing technology particles.

[0046] like Figure 2As shown, highly dispersed carbon particles result in irregular and unreproducible active electrodes, while low-dispersed carbon particles result in regular and reproducible active electrodes. According to existing technologies, highly defined structuring of the catalyst layer is impossible for carbon supports. This invention allows for controllable porous catalyst layers loaded with metal nanoparticles, which can increase power density or hydrogen production rates in fuel cells and electrolyzers by improving mass transport. Based on optimized interparticle and intraparticle porosity within the catalyst layer, the entire electrode becomes electrochemically accessible, which is not necessarily the case with conventional unstructured electrodes. This leads to better performance of 3D-structured electrodes using the same amount of expensive active catalyst material, or alternatively, allows for a reduction in expensive active catalyst metals while maintaining the same performance.

[0047] Furthermore, the reproducibility of the electrode is improved by using low-dispersion spherical carbon particles or carbon supports loaded with metal nanoparticles to construct the 3D structured electrode. The morphological properties of the catalyst layer ultimately depend to a large extent on the morphological properties of the low-dispersion carbon particles (tunable templated pore size and spherical particle size, dispersion). Other tunable properties of the low-dispersion carbon particles, namely the microstructuring of the carbon particles, enable further tuning possibilities for the electrode, such as conductivity, wettability, and corrosion resistance. In fuel cell catalysis as detailed in the exemplary section, 3D porous catalyst layers of monodisperse porous carbon particles loaded with metal nanoparticles show improvements in mass transport and catalysis compared to prior art Pt-loaded carbon materials. Here, to study the effect of the support, the catalytically active material is kept identical in both support systems.

[0048] It should be noted that the present invention may include any combination of the features and / or limitations mentioned herein, except for combinations of mutually exclusive features. For the purpose of illustrating the invention, the foregoing description is directed to specific embodiments of the invention. However, it will be apparent to those skilled in the art that many modifications and variations are possible with respect to the embodiments described herein. All such modifications and variations are intended to fall within the scope of the invention as defined in the appended claims.

[0049] Example The electrocatalyst consists of a carbon support and platinum, wherein the carbon support is Ketjenblack. ®EC300J (KB) and mesoporous N-doped carbon (MPNC) nanospheres. KB was purchased from Nouryon, while MPNC was synthesized based on a previously reported method (see Example 1 below). The active material used in this exemplary embodiment is Pt nanoparticles. The synthesis reactants H2PtCl6·6H2O (grade: Premier) and ethylene glycol (≥99%) were purchased from Alfa Aesar and Sigma-Aldrich, respectively. For the electrode ink, isopropanol (≥99.5%) and 800EW ionomer were purchased from Carl Roth and 3M, respectively. Fumatech fumapem was used. ® The FS715RFS (715 EW, 15 μm membrane) and Freudenberg H14Cx GDL were used for fuel cell testing. For the anode side of the fuel cell test, a Pt-based catalyst TEC10E50E (TKK) was purchased from Tanaka Kikinzoku Kogyo. O2, H2, and N2 (99.999% gas purity) were purchased from Sauerstoffwerke Friedrichshafen.

[0050] Example 1: Synthesis of carbon-supported mesoporous N-doped carbon (MPNC) nanospheres The synthesis of MPNC nanospheres was based on previous work by Melke et al. in “Electrochemical stability of silica-templated polyaniline-derived mesoporous N-doped carbons for the design of Pt-based oxygen reduction reaction catalysts” (Carbon 146, 2019, 44-59; https: / / doi.org / 10.1016 / j.carbon.2019.01.057) and “Investigating the Effect of Microstructure and Surface Functionalization of Mesoporous N-Doped Carbons on V 4+ / V 5+The method reported in "Kinetics" (ACS Appl. Energy Mater. 2020, 3, 12, 11627 - 11640; https: / / dx.doi.org / 10.1021 / acsaem.0c01489) was modified. Aniline was polymerized in the presence of nano-sized SiO2 particles via oxidative polymerization to form a polymer-SiO2 composite. The polymer-SiO2 composite was then carbonized at 1000 °C under N2, the template was removed by chemical etching, and the sample was washed. A final heat treatment step was performed at 500 °C under an inert atmosphere.

[0051] Figure 3 SEM images of the carbon-supported materials in SE (secondary electron) mode are shown: (a, b, c) KB and (e, f, g) MPNC-7-130. SEM image measurements were performed using a field emission gun high-resolution SEM SU8220 (Hitachi). The particle size distribution of (d) KB and (h) MPNC-7-130 was determined using multiple images recorded at magnifications of 200 kx and 50 kx, respectively.

[0052] Figure 4 Nitrogen physisorption measurements on KB and MPNC-7-130 at 77 K are shown on a 3P instrument machine, including (a) isotherms and (b) pore size distribution calculated via a quenched solid density functional theory model (QSDFT, adsorption branch of N2 on carbon at 77 K, considering slit / spherical / cylindrical pores). The measurements clearly demonstrate the well-defined mesoporosity of the MPNC sample. Part (c) shows the surface areas (BET, Brunauer-Emmett-Teller) of KB and MPNC-7-130, which are 785 m² and 785 m², respectively. 2 g -1 and 876m 2 g -1 .

[0053] Example 2: Deposition of Pt nanoparticles on carbon support Pt nanoparticles were synthesized on KB and low-dispersion MPNC nanospheres (templated with a pore size of 7 nm, an average particle size of 126 nm, and carbonized at 1000 °C (MPNC-7-130)) using a prior art ethylene glycol route: 350 mg of carbon support was dispersed in 200 mL of ethylene glycol and homogenized by vigorous stirring. H₂PtCl₆·6H₂O was dissolved in 100 mL of water and subsequently added to the carbon suspension. Thus, a specific amount of Pt precursor was used to obtain a Pt mass loading of 40 wt% based on the total mass of Pt and carbon. The suspension was stirred at 120 °C for 2 h and cooled to room temperature for 1 h. Finally, the sample was washed with boiling water until the supernatant was neutral and dried under vacuum at 80 °C.

[0054] Figure 5 Low-magnification SEM images (a) of Pt / MPNC-7-130 and XRD patterns (b) of electrocatalysts Pt / KB and Pt / MPNC-7-130 on a Bruker D8 Discover are shown, exhibiting the same XRD patterns and therefore the same Pt ​​crystallite size (2.3 nm according to the Scherrer equation). SEM images of electrocatalysts Pt / KB (in SE (secondary electron) modes c, g and TE (transmission electron) modes d, h) and Pt / MPNC-7-130 (in SE modes e, i and TE modes f, j) are also shown. SEM image measurements were performed using a field emission gun high-resolution SEM SU8220 (Hitachi) equipped with SE and TE detectors.

[0055] Example 3: Fabrication of porous catalyst layers on CCM and MEA Electrode active material was used as the cathode electrocatalyst and deposited on PEM. 100 mg of the electrocatalyst was homogenized in 4.97 g of deionized water, 1.24 g of isopropanol, and 0.77 g of ionomer dispersion (5% by weight in isopropanol) to obtain an I / C weight ratio of 0.65. The ink was placed in an ice bath and mixed for 60 minutes at 480 W using a high-precision ultrasonic instrument (Hielscher UIS250L). The dispersed ink was loaded into a spray gun (Sonaer Sono-Cell) and sprayed through a 60 kHz N2-driven nozzle onto a 5 cm × 5 cm film placed on an 80 °C hot plate. A 2 cm × 2 cm mask was applied to obtain a 4 cm film. 2 Limited battery area. 0.4 mg Pt / cm² 2 The target cathode mass loading was determined by gravimetric analysis and micro X-ray fluorescence (M4 Tornado, Bruker Nano GmbH).

[0056] For the ink on the anode side, 400 mg TKK was homogenized with 19.89 g DI water, 4.97 g isopropanol, and 3.11 g ionomer dispersion (5% by weight in isopropanol), and then sprayed onto the other side of the membrane using the same process. However, the anode loading was set to 0.1 mg Pt / cm³. 2 To ensure uniform gas distribution and prevent gas leakage, GDL and PTFE gaskets (130 μm thick) were applied to each of the two electrodes. The resulting MEA was clamped between a tortuous flow field and a fuel cell fixture (5 Nm, Scribner Associates).

[0057] Example 4: Electrochemical characterization of porous catalyst layer as cathode electrocatalyst in fuel cell Electrochemical characterization of the porous catalyst layer implemented in the CCM / MEA was performed on a test bench (Scribner Associates, Model 850e). The test protocol can be found in Table 1 below: Following conditioning of the MEA (step 1) and activation in O2 (steps 2 and 3), the cathode kinetics (mass activity) of the porous catalyst layer were investigated using polarization curves in O2 (step 4). Mass activity is expressed as A / g. Pt The current is calculated in units of 0.9V by dividing the Pt mass on the cathode side. The current is then corrected for ohmic losses and cross-current Ic (step 7). The polarization curve in step 5 applies a lower relative humidity in air, representing more realistic fuel cell conditions. Finally, a cyclic voltammogram is recorded (step 6), by adjusting Ic... c The corrected hydrogen underpotential deposition charge was integrated and normalized to 210 μC / cm. 2 (Corresponding to a polycrystalline Pt surface covered with the theoretically maximum amount of hydrogen) to calculate in m 2 / g Pt ECSA is expressed in units. The power density of a MEA is calculated by multiplying the applied current by the measured battery potential.

[0058] The results are shown in Figure 7 The polarization curves (a) of the porous catalyst layer material were obtained under the following conditions: anode: 0.25 L / min H2, cathode: 0.50 L / min 21% O2, 80 °C, 50% rH, 100 kPa. abs Pt / MPNC-7-130 exhibits higher voltage across the entire current density range than Pt / KB electrocatalysts based on existing carbon supports (with the same Pt ​​loading and particle size). Mass activity is shown in (b). ECSA is shown in (c). Peak power density is shown in (d). These demonstrate that the novel porous catalyst layer based on Pt / MPNC-7-130 exhibits improved performance across all categories. MEAs using Pt / MPNC-7-130 instead of Pt / KB at the cathode exhibit higher performance over the active range (0.9V), likely due to improved ionomer distribution / connection. Higher performance is also observed in the high current density range, likely due to better mass transport within the catalyst layer. Therefore, Pt / MPNC-based catalysts or MPNC-based carbon supports exhibit improved performance superior to existing Pt / KB technologies.

Claims

1. A porous catalyst layer comprising a porous carbon structure supported on metal nanoparticles, wherein the porous carbon structure is assembled from porous spherical carbon particles having a particle size distribution (Ð) of 1.2 or less and having a templated pore size having a templated pore size distribution (Ð') of 1.2 or less.

2. The porous catalyst layer according to claim 1, wherein the porous spherical carbon particles have a particle size of 10 nm to 5000 nm, preferably 25 nm to 2500 nm or 50 nm to 500 nm, and wherein the templated pore size is 1 nm to 1000 nm, preferably 2 nm to 500 nm or 5 nm to 100 nm.

3. The porous catalyst layer according to claim 1 or 2, wherein, based on the total weight of the porous carbon structure loaded with metal nanoparticles, the porous carbon structure has a metal nanoparticle loading of 1 wt% to 95 wt%, such as, for example, 5 wt% to 90 wt%, or 10 wt% to 85 wt%, or 15 wt% to 80 wt%, or 20 wt% to 75 wt%, or 25 wt% to 70 wt%, or 30 wt% to 65 wt%, or 35 wt% to 60 wt%, or 40 wt% to 55 wt%, or 45 wt% to 50 wt%.

4. The porous catalyst layer according to any one of claims 1 to 3, wherein the metal is a metal selected from Group 1, Group 2, Group 12, Group 13, Group 14, Group 15 or Group 16 of the periodic table, or a transition metal selected from Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11 or Group 12 of the periodic table, or a metal from the lanthanides or actinides, or a metalloid from Group 13, Group 14, Group 15, Group 16 or Group 17 of the periodic table, or wherein the metal is an alloy of any two or more metals and / or metalloids as defined above.

5. The porous catalyst layer according to any one of claims 1 to 4, wherein the diameter of the metal nanoparticles in any dimension does not exceed 100 nm, for example, 1 nm to 75 nm, or 2 nm to 60 nm, or 3 nm to 40 nm, or 4 nm to 25 nm, or 5 nm to 20 nm, or 7 nm to 15 nm, or 8 nm to 10 nm.

6. The porous catalyst layer according to any one of claims 1 to 5, wherein the interparticle pore volume of the porous carbon structure is 15% to 60%, for example 20% to 55%, or 25% to 50%, or preferably 26% to 48%.

7. The porous catalyst layer according to any one of claims 1 to 6, wherein the ratio of the volume of the internal pores of the particles to the volume of the interparticle pores is 0.05 to 3.0, preferably 0.1 to 2.0, and more preferably 0.7 to 1.

9.

8. The porous catalyst layer according to any one of claims 1 to 7, wherein the particle size distribution (Ð) of the porous spherical carbon particles and / or the templated pore size distribution (Ð') of the porous spherical carbon particles is 1.1 or less.

9. A porous carbon structure comprising two or more porous catalyst layers as defined in any one of the preceding claims, wherein the two or more porous catalyst layers are arranged in a layered manner.

10. The porous carbon structure according to claim 9, wherein each porous catalyst layer can have the same or different particle sizes, and / or wherein each porous catalyst layer can have the same or different templated pore sizes.

11. A method for producing a porous catalyst layer according to any one of claims 1 to 8, the method comprising the following steps: (i) Provide low-dispersion porous spherical carbon particles loaded with metal nanoparticles as defined in any one of claims 1 to 8; (ii) Mix the provided porous spherical carbon particles loaded with metal nanoparticles with one or more additives; (iii) The obtained mixture is applied to a substrate to form a porous carbon structure layer loaded with metal nanoparticles; (iv) Drying and / or curing the applied mixture to form a dried layer of porous carbon structure loaded with metal nanoparticles; as well as (v) Optionally, the dried layer of the porous carbon structure loaded with metal nanoparticles is calendered.

12. The production method according to claim 11, wherein the mixing step (ii) includes adding a dispersing medium to form an ink or paste, and wherein step (iii) is performed by 3D printing, slot coating, inkjet printing, doctor blade coating, spray coating, spin coating, or dip coating.

13. A membrane electrode assembly comprising one or more catalyst layers, the one or more catalyst layers being composed of or comprising the following: a porous carbon structure supported on metal nanoparticles according to any one of claims 1 to 8, or a porous carbon structure according to any one of claims 9 or 10.

14. The membrane electrode assembly of claim 13, wherein the one or more catalyst layers comprise one or more binders, such as polymer binders and / or ionomers.

15. Use of the porous catalyst layer according to any one of claims 1 to 8, or the porous carbon structure according to any one of claims 9 or 10, or the membrane electrode assembly according to any one of claims 13 or 14, in electrochemical energy conversion devices such as PEM / AEM fuel cells or PEM / AEM electrolyzers.

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