HK1208399B - Non-pgm catalyst for orr based on pyrolysed poly-complexes - Google Patents

Description

Non-platinum group metal catalysts for oxygen reduction reactions based on pyrolysed poly-composites

Cross Reference to Related Applications

The following application claims the benefit of U.S. provisional application 61/713,717 filed on day 10, 15, 2012, which is incorporated herein by reference in its entirety.

Background

Fuel cells are receiving increasing attention as a viable energy alternative. In general, fuel cells convert electrochemical energy into electrical energy in an environmentally clean and efficient manner. Fuel cells are expected to be a potential energy source for everything from small electronics to automobiles and homes. In order to meet different energy requirements, there are today many different types of fuel cells, each with different chemistries, requirements and uses.

As one example, Direct Methanol Fuel Cells (DMFCs) rely on the oxidation of methanol to form carbon dioxide on an electrocatalyst layer. Water is consumed at the anode and produced at the cathode. The positive ions (H +) are transported across the proton exchange membrane to the cathode where they react with oxygen to produce water. The electrons can then be transported from the anode to the cathode via an external circuit, providing power to an external source.

As another example, Polymer Electrolyte Membrane (PEM) fuel cells (also known as proton exchange membrane fuel cells) use pure hydrogen (typically supplied through a hydrogen storage tank) as the fuel. The hydrogen stream is delivered to the anode side of a membrane-electrode assembly (MEA) where it is catalytically split into protons and electrons. As with DMFC, positive ions are transported across the proton exchange membrane to the cathode where they react with oxygen to produce water.

One limiting factor in the wide-scale commercialization of PEM and DMFC fuel cells today is the cost associated with precious metals. Both DMFC and PEM fuel cells typically use platinum as the electrocatalyst. Precious metals (e.g., platinum) are required to catalyze the Oxygen Reduction Reaction (ORR) that is inactive at the cathode. One major route to overcome this limitation is to increase platinum utilization in noble metal-based electrocatalysts. Another possible route is to use less expensive, but still sufficiently active, catalysts in larger quantities. Several classes of non-platinum electrocatalysts have been identified as having sufficient oxygen reduction activity to be considered as potential electrocatalysts in commercial fuel cell applications.

In general, known non-platinum electrocatalysts are supported on high surface area carbon blacks. This is done to improve dispersion, active surface area and conductivity of the catalytic layer. The synthesis procedure typically involves precipitation of precursor molecules on a supporting substrate and pyrolysis of the supported precursor.

Metal-nitrogen-carbon (M-N-C) catalysts have found great promise for electrochemical oxygen reduction applications in fuel cell Membrane Electrode Assemblies (MEAs), stacks, and fuel cell systems. Decisive aspects of the material include the presence of metal particles, conjugated carbon-nitrogen-oxide-metal networks and nitrogen-bonded carbon. The metal phase includes metals, oxides, carbides, nitrides and mixtures of these states. The chemical state and combination of the N/C/M network and the N/C network affect performance, e.g., increased total nitrogen content improves ORR performance. However, these systems still suffer from several significant drawbacks, including: low stability in acidic environments, low durability in acidic and basic environments, high cost of nitrogen precursors, and low activity in ORR compared to platinum. The problem of low stability in acids is associated with leaching of metals from the carbon-nitrogen network. The low durability in acid and alkaline solutions translates into significant amounts of H evolution in these environments₂O₂It is corrosive to both metals and carbon-nitrogen networks. The low activity may be due to low metal loading and low concentration of active sites in such catalysts due to the use of external carbon sources (high surface carbons like Vulcan, ketjen black, etc.).

SUMMARY

In this disclosure, a method for preparing novel non-Platinum Group Metal (PGM) catalytic materials based on in situ polymerization of poly-composites on sacrificial supports using inexpensive and readily available precursors is described.

Brief Description of Drawings

FIG. 1 schematically illustrates the chemical structure of an exemplary polymer suitable for use in the presently disclosed methods.

FIG. 2 shows the RDE data of Fe-poly-melamine-formaldehyde prepared with temperature change of heat treatment, in the presence of oxygen₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1)。

FIG. 3 shows the RDE data for Fe-poly-urea-melamine-pyrrole-2-carbaldehyde prepared with a temperature change of the heat treatment, using O₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1)。

FIG. 4 shows RDE data for Fe-poly-dimethyltetrahydropyrimidinone-melamine-formaldehyde prepared with temperature change of heat treatment, using O₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1)。

Figure 5 shows the oxygen reduction reaction performance of representative catalysts produced using the methods described herein.

Figure 6 also shows the oxygen reduction reaction performance of representative catalysts produced using the methods described herein.

Detailed description of the invention

According to one embodiment, the present disclosure provides novel catalysts and catalytic materials and methods of making the same. According to a general embodiment, the present disclosure provides a method of forming a non-PGM catalyst based on in situ polymerization and templating of various reactive polymer precursors on a sacrificial support, followed by pyrolysis of the supported polymer, followed by final removal of the sacrificial support. According to various embodiments, polymerization may occur prior to or simultaneously with the templating step. For the purposes of this disclosure, the term "in situ polymerization" is used to indicate that at least a partial polymerization reaction occurs when reactants are exposed to a sacrificial support to templat on the sacrificial support. As described in more detail below, in some embodiments, polymerization is initiated prior to exposure to the sacrificial support (multi-step synthesis), but continues after exposure to the sacrificial support, while in other embodiments (single-step synthesis), polymerization is initiated only after exposure to the sacrificial support.

According to one embodiment, the reactive polymer used in the presently described process is a polymer comprising melamine, formaldehyde and/or urea (MCC) polymer precursors, which are used as sources of carbon and nitrogen in the final catalytic material. Exemplary MCC precursors suitable for use in the presently disclosed methods include melamine (M), formaldehyde (F), urea (U), imidazolidinyl urea (IMDZU), diazolidinyl urea (DAZU), and pyrrole-2-carboxaldehyde (2-PCA), and combinations thereof, according to various examples described herein. The chemical structures of these polymers are shown in FIG. 1. Other suitable materials include various combinations of urea, melamine, and aldehyde. Of course, those skilled in the art are familiar with the various chemicals and raw materials that can be used to obtain the MCC polymer precursor. For example, allantoin is a useful starting material for the synthesis of both diazolidinyl urea and imidazolidinyl urea. Similarly, dimethylformamide and pyrrole can be combined to prepare pyrrole-2-carbaldehyde. Thus, the present disclosure also includes those materials that are useful for producing MCC polymer precursors or MCC polymers under the synthetic conditions described herein or suitable for producing the results described herein.

While other groups have used high pressure and high temperature synthesis methods to produce supported catalytic materials formed from melamine and formaldehyde, the present disclosure provides a simple and inexpensive method for producing unsupported catalytic materials with less risk of damaging the materials used during the synthesis process. Furthermore, the presently disclosed methods are suitable for use with a wide variety of reactive polymers, as evidenced by the variety of materials in the examples section below.

For the sake of clarity, in the present application the term "catalyst" is used to refer to a final product having catalytic activity, suitable for use in, for example, a fuel cell. The catalyst may include various types of materials, some of which may not have catalytic activity per se (e.g., a support material). The term "catalytic material" is any material that has catalytic activity by itself or as part of a catalyst.

The present disclosure provides both single-step and multi-step synthetic methods for the catalytic materials described herein. In an exemplary single-step (or one-pot) synthesis method, a mixture of one or more metal precursors and one or more reactive polymer precursors are simultaneously infused and polymerized into a sacrificial support. The resulting material is then pyrolyzed, followed by final removal of the sacrificial support. Because the polymerization occurs in situ, the forming polymer can completely penetrate the three-dimensional structure of the sacrificial support, including any and all pores, recesses, ridges, etc., creating a precise negative template (negative) of the sacrificial support, enabling the formation of highly complex structures, e.g., having an extremely large surface area (determined by the shape of the sacrificial support), modified by a high concentration of metal active sites.

In general, it is recognized that the conditions suitable to allow simultaneous polymerization and templating depend on the particular material selected. However, as a general example of a one-pot synthesis method, polymer precursors (e.g., urea precursors, melamine and aldehyde precursors) are mixed in a suitable solvent, followed by the addition of an iron precursor and a sacrificial support. The polymerization may then be effected by an acid/base mechanism. After evaporation of the solvent, the resulting powder was cured in air at T = 150-. The dry powder may then be heat treated at T = 800-. The sacrificial support may then be removed by the medium in which it is soluble. According to some embodiments, after polymerization, the sacrificial support and the template polymer/metal active site precursor may be ball milled to grind the particles into a fine powder.

In one exemplary multi-step process, one or more reactive polymer precursors are first mixed together and polymerization is initiated. The polymerized polymer precursor and metal precursor are then introduced to the sacrificial support under suitable conditions such that the polymer and metal precursor are capable of templating on and within the sacrificial support. The process then continues with a heat treatment followed by removal of the sacrificial support as described above for the one-pot synthesis process.

Whether polymerization is initiated before exposure to the sacrificial support (multiple steps) or only after exposure (single step), the presently described methods provide for in situ polymerization of the polymer around the sacrificial support. It is recognized that in situ polymerization may, in some cases, result in different surface chemistries between the polymerized precursor and the sacrificial support, as the non-polymerized precursor has different support wetting ability and viscosity. For example, a hydrophilic precursor will coat the hydroxyl-coated support particles such that, after polymerization of the precursor, a more complete coating of the support particles is achieved. In contrast, a mixture of hydrophobic and hydrophilic precursors will produce a discontinuous coating of the support, resulting in gaps between the support and the polymer. These gaps will become pores after pyrolysis, resulting in different pore structures in the resulting catalyst. Thus, using in situ polymerization, and by specifically selecting materials that produce the desired degree of homogeneity and the nature of the contact between the precursor and the support, the presently described methods enable fine tuning of the morphology of the final product in a manner that cannot be achieved by mechanical mixing alone.

It is recognized that the sacrificial support itself may be synthesized and infused simultaneously, or the sacrificial support may be synthesized first (or otherwise obtained) and then infused with the desired polymer and metal precursor. The infused sacrificial carrier is then rendered inert (N)₂Ar, He, etc.) or reactive (NH)₃Acetonitrile, etc.) in an atmosphere.

According to one embodiment, the sacrificial support is infused with the reactive polymer and the iron precursor to produce the iron-containing catalytic material. The ratio of metal to reactive polymer precursor prior to synthesis can be any desired ratio. According to various specific examples, catalytic materials can be formed using a metal to polymer precursor ratio of 1:4 to 1:12, more specifically 1:6 to 1:10, more specifically 1: 8.

Suitable iron precursors include, but are not limited to, ferric nitrate, ferric sulfate, ferric acetate, ferric chloride, and the like. Further, it is recognized that other transition metals such as Ce, Cr, Cu, Mo, Ni, Ru, Ta, Ti, V, W, and Zr can be substituted for iron by simply using precursors of those metals instead. Exemplary transition metal precursors include, but are not limited to, cerium nitrate, chromium nitrate, copper nitrate, ammonium molybdate, nickel nitrate, ruthenium chloride, tantalum isopropoxide, titanium ethoxide, vanadium sulfate, ammonium tungstate, and zirconium nitrate. Furthermore, according to some embodiments, the presently described methods may utilize precursors of two or more metals to produce a multi-metal catalyst.

It is recognized, of course, that given the high temperatures that the sacrificial support will experience during the synthesis process, it is important to select a sacrificial support that is non-reactive to the catalytic material under the particular synthesis conditions used. Thus, it is recognized that silica is the preferred material for the sacrificial support, but other suitable materials may be used. Other suitable sacrificial supports include, but are not limited to, zeolites, alumina, and the like. The carrier may take the form of spheres, granules or other two-or three-dimensional regular, irregular or amorphous shapes. The spheres, particles, or other shapes may be monodisperse or irregular in size. The spheres, particles, or other shapes may or may not have pores, and such pores may be the same or different sizes and shapes.

It will be appreciated that the size and shape of the silica particles may be selected according to the desired shape and size of the voids within the electrocatalyst material. Thus, by selecting a particular size and shape of the silica particles, one can produce an electrocatalyst with voids of predictable size and shape. For example, if the silica particles are spheres, the electrocatalyst will contain a plurality of spherical voids. Those skilled in the art are familiar with electrocatalyst Pt-Ru black, which consists of a plurality of platinum-ruthenium alloy spheres. Electrocatalysts formed with silica spheres using the above method look like the negative image of Pt-Ru black; the space existing as a void in the Pt-Ru black is filled with the metal electrocatalyst, and the space existing as the metal electrocatalyst in the Pt-Ru black is a void.

As described above, according to some embodiments, silica spheres having any diameter may be used. In some preferred embodiments, the silica particles have a characteristic length of from 1 nm to 100 nm, in more preferred embodiments, silica particles having a characteristic length of from 100 nm to 1000 nm may be used, and in other preferred embodiments, silica particles having a characteristic length of from 1 mm to 10 mm may be used. Other mesoporous silicas may also be used in templated synthesis methods. In this case, templating involves intercalation into the mesopores of the material and results in a self-supported electrocatalyst with a porosity in the 2-20 nm range. In a specific embodiment, the silica template is Cabosil amorphous fumed silica (325 m)²In terms of/g). As noted above, since the spheres serve as templates for forming the electrocatalyst, in embodiments where silica particles having an average diameter of 20 nm are used, the spherical voids in the electrocatalyst are typically about 20 nm in diameter. Those skilled in the art are familiar with a variety of commercially available silica particles, and such particles can be used. Alternatively, known methods of forming silica particles can be employed to obtain particles having a desired shape and/or size.

As described above, after polymerization and templating of the reactive polymer precursor and the metal precursor on the sacrificial support, in an inert atmosphere (e.g., N)₂Ar or He) or in a reactive atmosphere (e.g. NH)₃Or acetonitrile) heat treating the material. When the infused material is nitrogen rich, an inert atmosphere is typically used because it is capable of generating a large number of active sites with Fe (or other metal) N4 centers. However, if the infused material is rich in carbon and lean in nitrogen, it may be desirable to use a nitrogen-rich atmosphere, as the nitrogen-rich atmosphere is capable of creating Fe (or other metal) N4 centers. As described in more detail in the experimental section below, according to some preferred embodiments, the materials of the invention are reactedSubjected to heat treatment in an atmosphere of sexual origin.

According to some embodiments, particularly embodiments in which only a single heat treatment is used, the optimal temperature for the heat treatment is typically in the range of 500 ℃ to 1100 ℃. According to some embodiments, the heat treatment may preferably be from 750 ℃ to 900 ℃, or more preferably from 775 ℃ to 825 ℃. In some embodiments, a heat treatment of about 800 ℃ is preferred, as our experimental data show that this temperature can produce a catalyst with a high amount of catalytic activity for certain specific materials (see experimental section below).

After the heat treatment, the sacrificial support is removed using suitable means. For example, the sacrificial carrier may be removed via chemical etching. Examples of suitable etchants include NaOH, KOH, and HF. According to some embodiments, it may be preferable to use KOH because it preserves all metals and metal oxides in the catalyst, and if the species is catalytically active, the use of KOH may actually increase catalytic activity. Alternatively, in some embodiments, HF may be preferred because it is very aggressive and can be used to remove some toxic species from the surface of the catalyst. Thus, one skilled in the art will be able to select the desired etchant based on the particular requirements of the particular catalytic material to be formed.

According to some embodiments, multiple heat treatment steps may be used. In this procedure, the polymer and metal precursors are polymerized and templated on a sacrificial support (as part of a one-pot or multi-step process) and subsequently subjected to a first thermal treatment step, such as pyrolysis, to produce an intermediate material enriched in unreacted iron. The intermediate material is then subjected to a second heat treatment step, which may be, for example, a second pyrolysis treatment, resulting in newly formed active sites. After the second heat treatment, the sacrificial carrier is removed using chemical etching or other suitable means, as described above.

In embodiments utilizing two separate heat treatment steps, it may be desirable to have different heat treatment steps performed under different conditions, e.g., at different temperatures and/or for different durations. For example, the first heat treatment step may be carried out at a relatively high temperature (e.g., 800 ℃) for 1 hour, and the second heat treatment step may be carried out at a temperature of 800-.

It is recognized that in some applications, single metal catalysts may not be sufficiently stable or active to replace traditional platinum-based or platinum alloy-based catalysts. Thus, as indicated above, the presently described methods may, according to some embodiments, use precursors of multiple metals in combination to achieve a desired stability and/or activity.

It is recognized that the presently described methods are capable of producing catalytic materials having highly complex morphological structures that produce high surface areas, which are highly desirable for catalytic reactions. According to various embodiments, the catalytic material described herein may have a surface area of at least 100m²g^-1At least 150 m²g^-1At least 200 m²g^-1At least 250 m²g^-1Or at least 300 m²g^-1。

According to some embodiments, it may be desirable to produce a large amount of the catalyst described herein, for example in a batch process. Thus, the present disclosure also provides a process for large scale preparation of the presently described catalyst. According to one embodiment, the present disclosure provides a method of combining a sacrificial support-based process with spray pyrolysis to produce a self-supported catalyst. According to this process, the spray pyrolysis process is a continuous process, whereas the sacrificial support based process is carried out batchwise. According to one exemplary method, the polymer and metal precursor materials described herein are mixed with a silica support, atomized, and dried in a tube furnace. The powder resulting from this procedure was then collected on a filter. The collected powder is subsequently heat treated. Finally, the sacrificial support is removed, for example by leaching with HF or KOH.

Of course, it is recognized that the catalysts described herein can also be produced by semi-batch or continuous operating processes. For example, all of the material may be loaded into a long screw-feeder that mixes the precursors while heating and moving them along the screw, resulting in the raw materials entering continuously at one end and the finished precursor/support mixture exiting continuously at the other end.

It is recognized that the above-described large-scale production methods are applicable to a wide variety of precursors and materials, and thus, are not necessarily limited to the catalysts disclosed herein.

The specific methods and compositions described herein are representative of preferred embodiments and are exemplary and not intended as limitations on the scope of the invention. Other objects, aspects and embodiments will occur to those skilled in the art upon consideration of the specification, and are included within the spirit of the invention as defined by the scope of the claims. It will be apparent to those skilled in the art that various substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein as essential. The methods and processes illustratively described herein suitably may be practiced in a different order of steps, and they are not necessarily limited to the order of steps indicated herein or in the claims. As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a catalyst" includes a plurality of such catalysts, and so forth.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, optional features, modifications and variations of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

All patents and publications referenced below and/or mentioned herein are indicative of the levels of those skilled in the art to which the invention pertains, and each such referenced patent and publication is hereby incorporated by reference to the same extent as if it were individually incorporated by reference in its entirety or set forth herein in its entirety. Applicants reserve the right to naturally incorporate into this specification any and all materials and information from any such cited patents or publications.

Additional information may be gathered in the examples section below. The reaction tests shown and described in the figures and in the examples below clearly demonstrate that the catalysts prepared using the described process have high oxygen reduction activity in an acid medium. In addition, the mechanism of oxygen reduction shows that the direct reduction of oxygen to water through a 4 electron path prevents the generation of corrosive peroxides, thus improving the stability and durability of the catalyst. Thus, the catalysts of the compositions and methods of preparation using the methods described herein (including but not limited to the materials described herein shown) are effective catalysts for oxygen reduction.

Examples

I. A multi-step process.

Synthesis and analysis of Fe-imidazolidinyl-urea-melamine-formaldehyde (Fe-IMDZU-M-F) catalyst

The Fe-imidazolidinyl-urea-melamine-formaldehyde (Fe-IMDZU-M-F) catalyst is prepared in a two-step process.

20g imidazolidinyl urea was dissolved in 200 ml of water. The temperature of the solution was increased to 80 ℃. 12g of melamine were added to the solution, followed by 40ml of formaldehyde. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours.

25g of the polymer prepared were admixed with 10g of fumed silica (Cab-O-Si)l^TMEH-5, surface area: to 400 m²g^-1) And 2.75g of ferric nitrate were ball milled. The solid was ground to a fine powder in a ball mill and subsequently subjected to Heat Treatment (HT). The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

Synthesis and analysis of Fe-diazolidinyl-urea-melamine-formaldehyde (Fe-DAZU-M-F) catalyst

The Fe-diazolidinyl-urea-melamine-formaldehyde (Fe-DAZU-M-F) catalyst is prepared in a two-step process.

43g diazolidinyl urea are dissolved in 400 ml water. The temperature of the solution was increased to 80 ℃. 23g of melamine were added to the solution, followed by 140ml of formaldehyde. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours.

25g of the polymer prepared were admixed with 10g of fumed silica (Cab-O-Sil)^TMEH-5, surface area: to 400 m²g^-1) And 2.75g of ferric nitrate were ball milled. The solid was ground to a fine powder in a ball mill and subsequently subjected to Heat Treatment (HT). The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

Synthesis and analysis of Fe-urea-melamine-pyrrole-2-carbaldehyde (Fe-U-M-2PCA)

The Fe-urea-melamine-pyrrole-2-carbaldehyde (Fe-U-M-2PCA) catalyst was prepared in a two-step process.

13g of urea was dissolved in 100ml of water. The temperature of the solution was increased to 80 ℃. 23g of melamine were added to the solution, followed by 120ml of pyrrole-2-carbaldehyde. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours.

25g of the polymer prepared were admixed with 10g of fumed silica (Cab-O-Sil)^TMEH-5, surface area: to 400 m²g^-1) And 2.75g of ferric nitrate were ball milled. The solid was ground to a fine powder in a ball mill and subsequently subjected to Heat Treatment (HT). The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

II, one-pot synthesis.

Silica EH5 was dispersed in 100ml of water. 23g of urea are dissolved in 100ml of water and added to the silica suspension. The temperature of the solution was increased to 80 ℃. 23g of melamine were added to the solution, followed by 120ml of pyrrole-2-carbaldehyde and 26g of Fe (NO)₃)₃. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours. The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃。

Silica EH5 was dispersed in 100ml of water. 18g of urea are dissolved in 100ml of water and added to the silica suspension. The temperature of the solution was increased to 80 ℃. 23g of melamine were added to the solution, followed by 19g of pyridylaldehyde and 4g of Fe (NO)₃)₃. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours. The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

Silica EH5 was dispersed in 100ml of water. 10g of picolinamide are dissolved in 100ml of water and added to the silica suspension. The temperature of the solution was increased to 80 ℃. 29g of melamine were added to the solution, followed by 100ml of pyrrole-2-carbaldehyde and 29g of Fe (NO)₃)₃. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours. The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

Silica EH5 was dispersed in 100ml of water. 30g of dimethyltetrahydropyrimidinone were dissolved in 100ml of water and added to the silica suspension. The temperature of the solution was increased to 80 ℃. 23g of melamine were added to the solution,120ml of formaldehyde and 39g of Fe (NO) are then added₃)₃. After 30 minutes, 1ml of 1M KOH was added to the solution and the mixture was stirred for 1 hour. 2.5ml of concentrated H are added₂SO₄To polymerize the precursor. The mixture was dried on a hot plate at T =145 ℃. The dried powder was cured at T =185 ℃ for 48 hours. The heat treatment conditions are as follows: at a rate of 100 cc min^-1In a UHP N2 atmosphere at a HT temperature of 850 ℃ and a HT temperature ramp rate of 10 ℃ for 10 ℃ min^-1And HT duration is 1 hour. The silica support was removed by 25 wt% HF solution at room temperature for 24 hours. The powder was washed with deionized water until pH =6 and dried overnight at T =85 ℃.

The RDE data for representative catalysts produced using the methods described herein are presented in fig. 2-4. FIG. 2 shows the RDE data of Fe-poly-melamine-formaldehyde prepared with varying heat treatment temperatures, using O₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1). FIG. 3 shows the RDE data for Fe-poly-urea-melamine-pyrrole-2-carbaldehyde prepared with a temperature change of the heat treatment, using O₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1). FIG. 4 shows RDE data for Fe-poly-dimethyltetrahydropyrimidinone-melamine-formaldehyde prepared with temperature change of heat treatment, using O₂Saturated 0.5M H₂SO₄Middle (catalyst loading: 600. mu.g cm)^-2，1200RPM，5mV s^-1)。

The oxygen reduction reaction performance of representative catalysts produced using the methods described herein is presented in fig. 5 and 6. Performance in MEA testing demonstrated that non-platinum group metal catalysts based on pyrolyzed poly-composites were active for oxygen reduction reactions. Furthermore, the catalyst performance in the kinetic control of MEA performance shown in figures 5 and 6 demonstrates that the performance of the catalyst is not kinetically limited and can improve the true performance of these catalytic materials.

Claims (17)

1. A method for forming a catalytic material, the method comprising:

providing sacrificial template particles;

templating a mixture of reactive polymer precursors and metal precursors on the sacrificial template particles under suitable conditions such that the reactive polymer precursors can be polymerized in situ to produce a sacrificial template coated with a reactive polymer containing dispersed electrocatalytic material precursors;

heat treating the dispersed electrocatalytic material precursor; and

the sacrificial template particles are removed to produce a highly dispersed self-supported high surface area electrocatalytic material.

2. The method of claim 1, wherein the reactive polymer precursor is selected from the group consisting of: melamine, formaldehyde, urea, and combinations thereof.

3. The method of claim 1, wherein the reactive polymer precursor is selected from the group consisting of: melamine, formaldehyde, urea, imidazolidinyl urea, diazolidinyl urea, and pyrrole-2-carbaldehyde, and combinations thereof.

4. The method of claim 1, wherein the metal precursor is a precursor of iron.

5. The method of claim 2, wherein the metal precursor is ferric nitrate.

6. The method of claim 1, wherein heat treating the dispersed precursor comprises pyrolysis.

7. The process of claim 1, wherein suitable conditions to enable in situ polymerization comprise addition of an acid.

8. The method of claim 7, wherein the acid is H₂SO₄。

9. The method of claim 4, wherein the heat treating comprises a first pyrolysis conducted at a temperature in excess of 750 ℃ and less than 900 ℃.

10. The method of claim 1, further comprising a second pyrolysis.

11. The method of claim 1, wherein the sacrificial template coated with the reactive polymer containing the dispersed electrocatalytic material precursor is ball milled to form a fine powder prior to the thermal treatment.

12. An unsupported catalytic material comprising a plurality of highly dispersed active metal sites and a significant portion of carbon and nitrogen generated from a polymer formed from melamine, formaldehyde, urea, imidazolidinyl urea, diazolidinyl urea, pyrrole-2-carbaldehyde, or a combination thereof, formed from:

providing sacrificial template particles;

simultaneously templating a mixture of reactive polymer precursors and metal precursors on the sacrificial template particles under suitable conditions such that the reactive polymer precursors can be polymerized in situ to produce a sacrificial template coated with a reactive polymer containing dispersed electrocatalytic material precursors;

heat treating the dispersed electrocatalytic material precursor; and

the sacrificial template particles are removed to produce a highly dispersed self-supported high surface area electrocatalytic material.

13. The unsupported catalytic material of claim 12 wherein the unsupported catalytic material has a surface area of at least 300 m²g^-1。

14. The unsupported catalytic material of claim 12 wherein the reactive polymer precursor is selected from the group consisting of: melamine, formaldehyde, urea, or a combination thereof.

15. The unsupported catalytic material of claim 12 wherein the metal precursor is a precursor of iron.

16. The unsupported catalytic material of claim 12 wherein the metal precursor is ferric nitrate.

17. The unsupported catalytic material of claim 12 wherein the sacrificial template coated with a reactive polymer containing dispersed electrocatalytic material precursors is ball milled to form a fine powder prior to heat treatment.