HK1212945B - Carbendazim-based catalytic materials - Google Patents

Description

Catalytic material based on befitinib

Cross Reference to Related Applications

The following application claims the benefit of U.S. provisional application No. 61/593,542, 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 enable electrochemical energy to be converted into electrical energy in an environmentally clean and efficient manner. Fuel cells are also contemplated as a potential energy source for a variety of items ranging from small electronic devices to automobiles and homes. To meet different energy requirements, there are now many different types of fuel cells, each with different chemical compositions, needs and uses.

As one example, Direct Methanol Fuel Cells (DMFCs) rely on the oxidation of methanol to 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 through an external circuit to provide 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 provided from a hydrogen tank) as the fuel. The hydrogen stream is transported to the anode side of a membrane-electrode assembly (MEA) where it is catalytically decomposed 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 of the limiting factors in the large-scale commercialization of PEM and DMFC fuel cells today is the cost associated with the precious metals. Both DMFC and PEM fuel cells typically use platinum as the electrocatalyst. Catalyzing the slow Oxygen Reduction Reaction (ORR) at the cathode requires a noble metal, such as platinum. One of the main approaches to overcome this limitation is to increase the platinum utilization in noble metal-based electrocatalysts. Another possible approach is to use a larger amount of a less expensive catalyst, which is still sufficiently active. Several non-platinum electrocatalyst classes have been identified as having sufficient oxygen reduction activity to be considered potential electrocatalysts in commercial fuel cell applications.

Generally, known non-platinum electrocatalysts are supported on high surface area carbon blacks. This is done to increase the dispersion, active surface area and conductivity of the catalytic layer. The synthesis step typically includes precipitation of precursor molecules on a supported 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. Key aspects of the material include the presence of metal particles, conjugated carbon-nitrogen-oxide-metal networks, and nitrogenBound carbon. The metal phase includes oxides, carbides, nitrides and mixtures of these states of the metal. The chemical state and bonding of the N/C/M network and the N/C network affect performance, e.g., increasing total nitrogen content improves ORR performance. However, these systems still have 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. Low durability in acid and alkaline solutions results from the release of significant amounts of H in these environments₂O₂Explained by H₂O₂Both corrosive to metals and carbon-nitrogen networks. The low activity may be due to low metal loading and to the use of external carbon sources (high surface carbons, such as Vulcan, ketjen black, etc.) resulting in low concentrations of active sites in these catalysts.

SUMMARY

A method for preparing a bafilbert (M-CBDZ) -based catalytic material using a sacrificial support approach and using inexpensive, readily available precursors is described in the present disclosure.

Brief Description of Drawings

Fig. 1 is the chemical formula of befenate.

Fig. 2 is an SEM image of CBDZ catalyst without iron.

FIG. 3 is an SEM image of the Fe-4CBDZ catalyst.

FIG. 4 is an SEM image of the Fe-12CBDZ catalyst.

Fig. 5 shows a high resolution N1 s spectrum of pyrolyzed CBDZ.

FIG. 6 shows a high resolution N1 s spectrum of Fe-2CBDZ pyrolyzed at 800 ℃.

FIG. 7 shows a high resolution N1 s spectrum of Fe-CBDZ pyrolyzed at 900 ℃.

FIG. 8 shows the high resolution N1 s spectra of Fe-CBDZ subjected to a second pyrolysis step in an ammonia atmosphere.

FIG. 9 is a graph showing the change in% atomic of N and relative% of different N species as a function of T for pyrolysis.

FIG. 10 shows RRDE data for Fe-CBDZ catalysts with varying Fe: CBDZ ratios: CBDZ (━ ━), Fe-4CBDZ (━ ━), Fe-6CBDZ (. eta.), Fe-8CBDZ (━. ━), Fe-10CBDZ (━. ━) and Fe-12CBDZ (. eta.). Conditions are as follows: 0.5M H2SO4 saturated with O2, 1200RPM, 5mV s-1, catalyst loading 0.6mg cm-2.

FIG. 11 shows RRDE data for Fe-8CBDZ catalysts heat treated at different temperatures: t =750 ℃ (━ ━), T =800 ℃ (━ ━), T =850 ℃ (. -), and T =900 ℃ (=). Conditions are as follows: 0.5M H2SO4 saturated with O2, 1200RPM, 5mVs-1, catalyst loading 0.6mg cm-2.

FIG. 12 shows RRDE data for a second heat treated Fe-CBDZ catalyst in different atmospheres: fe-8CBDZ with a single heat treatment (━ ━), Fe-8CBDZ with two heat treatments in nitrogen (━ ━), and Fe-82CBDZ with two heat treatments in ammonia (…). Conditions are as follows: with O₂Saturated 0.5M H₂SO₄，1200RPM，5mV s^-1Catalyst loading 0.6mg cm^-2。

FIG. 13 is a graph showing the% atoms of the N pyridine center as E for all Fe-CBDZ electrocatalysts_1/2A graph of the function of (c).

FIG. 14 is a graph showing N for all Fe-CBDZ electrocatalysts₄-the% atoms of the Fe center as E_1/2A graph of the function of (c).

FIG. 15 shows an image of display N₄-graph of% atomic of Fe centres as a function of the loading of the precursors, all pyrolyzed at 800 ℃.

FIG. 16 is a graph of DoE durability data obtained by the RRDE method for Fe-8CBDZ, Fe-8CBDZ in BoL (━ ━), Fe-8CBDZ after 1000 cycles (━ ━), Fe-8CBDZ after 5000 cycles (. eta.) and Fe-8CBDZ after 10000 cycles (━. ━). Conditions are as follows: with O₂Saturated 0.1M H₂SO₄，900RPM，50mV s^-1Catalyst loading 0.2mg cm^-2。

FIG. 17 is a graph showing MEA performance of Fe-8CBDZ catalyst from a single heat treatment of Fe-8CBDZ (■), in N₂Fe-8CBDZ (●) and in NH₃Fe-8CBDZ (▲) of two heat treatments in (1): 100% RH, O2/H2, anode flow rate: 100ccm, cathode flow rate: 100ccm, 30psig, cell T =80 ℃.

Detailed description of the invention

According to one embodiment, the present disclosure provides novel catalysts and catalytic materials and methods of making the same. In contrast to many of the aforementioned methods of preparing M-N-C-based catalytic materials using starting materials that are known to complex with iron and/or be of a chelate-like structure, the present disclosure utilizes the precursor benetite (CBDZ) that does not typically form complexes with iron and has a non-chelate structure. The chemical structure of baftint is shown in figure 1. Bafenate is well known as a broad spectrum benzimidazole formate fungicide. However, in the present disclosure, befenate is used as a carbon precursor in forming new high activity non-PGM catalysts for redox reactions.

For clarity, in the present application, the term "catalyst" is used to refer to a catalytically active end product suitable, for example, for use in 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 is catalytically active by itself or as part of a catalyst.

The present disclosure provides single and two-step synthesis methods for the bafibertine-based catalytic materials described herein. Both steps rely on the introduction of befenacin on a sacrificial support and pyrolysis of the resulting material.

According to a more specific single-step example, the catalytic material of the present disclosure can be synthesized by impregnating a sacrificial support with befenate and, if desired, a metal precursor. The ratio of metal to befenate prior to synthesis can be any desired ratio. According to various specific examples, catalytic materials can be produced in which the metal is iron and has a Fe: Befenate ratio (Fe: CBDZ) of 1:4 to 1:12, more specifically 1:6 to 1:10, more specifically 1: 8.

It will be appreciated that the sacrificial support may be synthesized and impregnated in a single synthesis step, or the sacrificial support may be synthesized (or otherwise obtained) first and then impregnated with the bafil and suitable metal precursor. The impregnated sacrificial support is then rendered inert (N)₂Ar, He, etc.) or reactive (NH)₃Acetonitrile, etc.) is subjected to a thermal treatment (e.g., pyrolysis).

According to one embodiment, the sacrificial support is impregnated with befenacin and an iron precursor. Suitable iron precursors include, but are not limited to, ferric nitrate, ferric sulfate, ferric acetate, ferric chloride, and the like. In addition, it will be appreciated that other transition metals may be used in place of iron by simply using precursors of those metals, such as Ce, Cr, Cu, Mo, Ni, Ru, Ta, Ti, V, W and Zr. 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. Additionally, according to some embodiments, the presently described methods may prepare multi-metal catalysts from precursors of two or more metals.

It will, of course, be appreciated that given the high temperatures experienced by the sacrificial support 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 will be appreciated that silica is a preferred material for the sacrificial support, but other suitable materials may also 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 of irregular size. The spheres, granules or other shapes may or may not have pores, which 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 particle size and shape of the silica particles, an electrocatalyst with voids of predictable size and shape can be prepared. For example, if the silica particles are spheres, the electrocatalyst will comprise a plurality of spherical voids. Those skilled in the art will be familiar with electrocatalyst Pt-Ru black, which consists of a plurality of platinum-ruthenium alloy spheres. The electrocatalyst formed by using silica spheres by the above method looks like a negative image of Pt-Ru black in which the space existing as voids is filled with a metal electrocatalyst and in which the space existing as a metal electrocatalyst is voids.

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

As described above, after deposition and/or impregnation of the befenacin and metal precursor on the sacrificial support, in an inert atmosphere, e.g. N₂Heat treating the material in Ar or He, or in a reactive atmosphere such as NH₃Or heat treatment in acetonitrile. When the impregnated material is rich in nitrogen, an inert atmosphere is generally used, since it enables the production of a deviceThere are a number of active sites centered on Fe (or other metal) N4. However, if the impregnated material is carbon rich and nitrogen poor, it may be desirable to use a nitrogen rich atmosphere, as the nitrogen rich atmosphere enables the creation of Fe (or other metal) N4 centers. As described in more detail in the experimental section below, according to some preferred embodiments, the material of the present invention is subjected to a heat treatment in a reactive atmosphere.

According to some embodiments, particularly embodiments in which a single-step synthesis process 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 between 750 ℃ and 900 ℃, or more preferably between 775 ℃ and 825 ℃. In some embodiments, heat treatment at about 800 ℃ is preferred because our experimental data shows that this temperature produces a catalyst with a high catalytically active amount for certain specific materials (see experimental section below).

After the heat treatment, the sacrificial carrier is removed by a suitable method. For example, the sacrificial carrier may be removed by chemical etching. Examples of suitable etchants include NaOH, KOH, and HF. According to some embodiments, it may be preferable to use KOH because it keeps all metals and metal oxides in the catalyst, and if these species are 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 may be used to remove some toxic species from the catalyst surface. Thus, one skilled in the art should be able to select the desired etchant according to the particular requirements of the particular catalytic material to be formed.

As mentioned above, the catalytic materials described so far can also be synthesized in a two-step process. In this procedure, to prepare an intermediate material rich in unreacted iron, the befenacin and the metal precursor are immersed in a sacrificial support and then subjected to a first heat treatment step, for example pyrolysis. The intermediate material is then subjected to a second heat treatment step, which may be, for example, a second pyrolysis treatment, resulting in newly generated active sites. After the second heat treatment, the sacrificial carrier is removed by chemical etching as described above or other suitable means.

In embodiments utilizing a two-step process, and thus utilizing two separate heat treatment steps, it may be desirable to perform the different heat treatment steps 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 higher temperature (e.g., 800 ℃) for 1 hour, and the second heat treatment step may be carried out at a temperature of 800-.

As described in more detail in the examples section below, in contrast to conventional synthesis methods, the sacrificial support-based methods described herein avoid the use of carbon supports, resulting in higher surface areas and 3D porous structures. According to some embodiments, the catalytic material formed during thermal decomposition of the Fe-CBDZ composite comprises a substantial amount (i.e., greater than 75%) of carbon derived from befenate. Thus, greater than 75%, 80%, 85%, 90%, 95%, 99% of the carbon in the composite may be derived from CBDZ. According to some embodiments, all (100%) of the carbon sources in the composite material are from CBDZ. Finally, the resulting catalytic material is self-supporting after removal of the sacrificial support and has a high active site density.

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

According to some embodiments, it may be desirable to prepare a large amount of the catalyst described herein, for example, in a batch process. Thus, the present disclosure also provides a method for large scale preparation of the presently described catalysts. According to one embodiment, the present disclosure provides a method of combining a sacrificial support-based process with spray pyrolysis to prepare a self-supported catalyst. According to this method, the spray pyrolysis process is a continuous process, whereas the sacrificial support based process is carried out batchwise. According to one exemplary method, the befenate 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 then heat treated. Finally, the sacrificial support is removed, for example by leaching with HF or KOH.

It will be appreciated that the large scale preparation methods described above are applicable to a wide range of precursors and materials and, therefore, 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 are not intended as limitations on the scope of the invention. Other objects, aspects and embodiments will occur to those skilled in the art upon studying the specification, and are included within the spirit of the invention as defined by the scope of the appended 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 different step sequences, which are not necessarily limited to the step sequences specified 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 the like.

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 and optional features, modification and variation 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 cited below and/or mentioned herein are indicative of the levels of skill of those skilled in the art to which this invention pertains, and each such cited patent or publication is 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 physically incorporate into this specification any and all materials and information from any such cited patents or publications.

Additional information may be gleaned from the examples section below. The reaction experiments shown and described in the figures and in the examples below clearly show that the catalysts prepared by the process have a high oxygen reduction activity in an acid medium. In addition, the mechanism of oxygen reduction shows that oxygen is directly reduced to water through the 4-electron pathway, preventing corrosive peroxides from being generated, and thus improving the stability and durability of the catalyst. Thus, the composite catalysts (including but not limited to the materials described herein) prepared using the preparation methods described herein are effective catalysts for oxygen reduction.

Example (b):

1. Fe-CBZD catalyst synthesis

The Fe-CBDZ catalyst was prepared by a sacrificial support method. First, a calculated amount of silica (Cab-O-Sil) was dispersed in water in an ultrasonic bath^®L90, surface area 90m²g^-1). Then, an aqueous suspension of befenati (Carbendazim, Sigma-Aldrich) was added to the silica and sonicated for 20 minutes. Finally, ferric nitrate (Fe (NO)₃)₃*9H₂O, Sigma-Aldrich) was added to SiO₂CBDZ solution and sonicated for 8 hours (total metal loading on silica calculated as 15% by weight). After sonication, the viscous solution of silica and Fe-CBDZ was allowed to dry overnight at T =85 ℃. The resulting solid material was ground to a fine powder in an agate mortar and then subjected to Heat Treatment (HT). The overall condition of HT was UHP nitrogen (flow rate 100cc min)^-1)，20° min^-1A temperature ramp rate, and a 1.5 hour pyrolysis time. The test variables for HT temperature were 750 deg.C, 800 deg.C, 850 deg.C and 900 deg.C. After heat treatmentThe silica was leached overnight with 25 wt% HF. Finally, the Fe-CBDZ material was washed with DI water until a neutral pH was reached, then dried at T =85 ℃. In the inert (N)₂) Or reactive (NH)₃) The second heat treatment was performed for 30 minutes at T =950 ℃ in an ammonia atmosphere. To evaluate the effect of the second heat treatment on the catalytic activity, the reaction was carried out under inert conditions (N)₂) Or reactive (NH)₃) And (3) in the atmosphere, carrying out heat treatment on the material with the best performance at T =950 ℃. The same synthesis was performed with just befenacin to enable comparison of the activity of the non-iron added befenacin with the activity of the iron-containing material.

In the experiments in which the change in the Fe: CBDZ mass ratio was compared, the catalysts synthesized were Fe-4CBDZ, Fe-6CBDZ, Fe-8CBDZ, Fe-10CBDZ and Fe-12CBDZ without the addition of iron.

In the experiments in which the change in the Fe: CBDZ mass ratio was compared, the catalysts synthesized were Fe-4CBDZ, Fe-6CBDZ, Fe-8CBDZ, Fe-10CBDZ and Fe-12CBDZ without the addition of iron. CBDZ ratio, as used herein, refers to the initial mixture of ferric nitrate and befenacin in the following amounts prior to heat treatment: 1g Fe (NO)₃)₃:4g CBDZ、1g Fe(NO₃)₃:6g CBDZ、1g Fe(NO₃)₃:8g CBDZ、1g Fe(NO₃)₃10g CBDZ and 1g Fe (NO)₃)₃:12g CBDZ。

2. Ring disk electrode

Electrochemical analysis of the synthesized catalyst was performed using an electrochemical analysis system of Pine Instrument Company. The reported spin rate is 1200RPM and the scan rate is 5mV sec^-1. The electrolyte is O at room temperature₂Saturated 0.5MH₂SO₄. A platinum wire counter electrode and an Ag/AgCl reference electrode were used.

By mixing 5mg of Fe-CBDZ electrocatalyst with 850. mu.L isopropanol and 150. mu.L Nafion^®Polymer (0.5% by weight, DuPont) prepared the working electrode. The mixture was sonicated and then 30. mu.L was applied to a sample having a thickness of 0.2474cm²A glassy carbon disc of cross-sectional area. The catalyst loading on the electrode was 0.6mg cm-2.

3. Doe durability protocol for non-PGM cathode catalysts

As described above, with reduced catalyst loading (0.2mg cm)^-2) And preparing a working electrode. The electrolyte is O₂Saturated 0.1M H₂SO₄. Using 50mV s^-1Scanning rate, durability test was performed at 900RPM rotation rate. The potential range was chosen according to the DoE recommendation, 0.2-1.1V relative to RHE.

4. MEA fabrication and testing

By mixing 75mg of catalyst with 1.2g of 5% by weight Nafion^®Polymer solution and 3.5ml IPA (solid Nafion)^®Nominal polymer content 45 wt.%), an ink for MEA was prepared. The mixture was sonicated in an ultrasonic bath for 2 hours. Spraying with hand to make 4mg cm^-2Catalyst deposition to 5cm²On the surface of SGL 25BC carbon paper. Anode was hot pressed by T =135 deg.C, T =3 minutes and 1000 pounds pressure (Pt/C JM 0.5mg cm)^-2) Membrane (Nafion)^®N211 polymer) and hand-sprayed cathode to assemble the MEA.

The test conditions were selected as: o is₂/H₂T cell =80 ℃, 100% RH, anode and cathode flow rate 100 ccm.

5. Results and discussion

Morphological analysis of the bafibertine and Fe-CBDZ materials synthesized with different Fe: CBDZ mass ratios showed that all materials had well-generated porous structures (fig. 2-4). Macropores are formed during leaching of agglomerated silica, while the micropores remove SiO alone₂Particles (-30 nm) are formed. All materials have similar surface areas (-600 m)²g^-1). As can be seen by comparing fig. 2-4, increasing the concentration of befenacin did not affect morphology.

XPS analysis shows that the material consists mainly of carbon with several atomic percent of nitrogen and oxygen. Since the unreacted iron was dissolved in HF, the iron content was determined to be 0.1-0.3 atomic%. FIGS. 5-8 show the results of N1 s curve fitting for a subset of samples. The largest peak in the metal-free sample is pyrroleN at 400.7 eV. Significant amounts of nitrile (398eV), pyridine (398.6eV) and amine (399.6eV) were also present with small amounts of quaternary nitrogen (401.8eV) and graphite (403eV) nitrogen. It has been shown previously that pyrrole nitrogen is responsible for O₂To H₂O₂The main type of nitrogen of the first 2 e-step of the reduction. With the exception of all these peaks, the spectra of all samples containing Fe are curves fitted with two peaks resulting from N-metal coordination. The first is Fe-N₂Limited to having a shift from pyridine nitrogen +0.8eV (399.4eV), another type is Fe-N₄The shift from pyridine is 1.1eV (399.7 eV). The latter is the exact position of the amine group in the metal-free sample. Fig. 9 follows the release of the above species as a function of pyrolysis temperature. It can be seen that the total nitrogen amount is significantly reduced. With higher pyrolysis temperature, most of the Fe-N₂The center disappears. Pyridine nitrogen is also reduced, and Fe-N₄The amount of centers increased and the pyrolysis temperature reached a maximum at 850 ℃. Although not shown, it was also observed that quaternary nitrogen disappeared at higher temperatures, while graphite nitrogen increased.

We have previously shown that for two classes of N-C precursors (4-amino-antipyrine and polyethyleneimine), heat-treated metal-free materials have very low activity and produce significant amounts of H₂O₂This shows that the use of the 2 e-mechanism (see, e.g., A. Serov, M.H. Robson, K. Artyushkova, P. Atanassov "patterned Non-PGM catalyst Derived from Iron and poly (ethyleneimine) precursors) applied. Catal. B127 (2012) 300. 306 and A. Serov, M.H. Robson, B. Halevi, K. Artyushkova, P. Atanassov" high Active and dual patterned Non-PGM Catalysts Derived from Iron and Aminoantipyrine) modified metals from Iron and poly (ethyleneimine) precursors, and that the high PGM Active and durable Non-PGM Catalysts Derived from Iron and Aminoantipyrine (2012-Irironed) are incorporated herein by reference, Com.53). The optimization of the Fe: CBDZ ratio and the effect of befenacin concentration on ORR activity are shown in figure 10. It has been demonstrated that iron-free materials based on CBDZ have significantly lower ORR performance and produce up to 8 times as much peroxide as Fe-CBDZ materials. As shown, Fe-CBDZ materials with Fe: CBDZ =1:8 mass ratio showed the bestAnd this ratio was selected for other tests.

It has previously been established that heat treatment parameters play a critical role in Catalytic Activity (see, for example, F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J. -P. Dodelet, G. Wu, H.T. Chung, C. M. Johnston, P. Zeleny Energy Environ. Sci. 4 (2011) 114. M.H. Robson, A.Serov, K. Artyuskova, P. Atanassov "A mechanical Study of 4-amino organic Catalytic and Iron Derived Catalytic Non-Platinum Group Catalyst Group reaction of the Oxygen reduction reaction" (the mechanism of the reaction of a Non-metallic Catalyst obtained from 4-amino benzoic and PGM) Acimplementation of Catalytic Activity of Fe-Catalytic reaction of the Oxygen reduction reaction of PGM. P. Heterophylloton, P. thermo-Catalytic reaction of PGM;, P. Softorv. O. P. The et al, et al ) (iii) electric, Acta, 87 (2013) 361-365, A. Serov, M.H. Robson, K. Artyushkova, P. Atanassov "patterned Non-PGM catalyst derived from Iron and poly (ethyleneimine) precursors, applied. Cat. B127 (2012) 300-306, A. Serov, M.H. Robson, M. Smollik, P. Atanassov" patterned bi-metallic Non-PGM catalyst for oxygen reduction "PGM 80 (PGM) 213, PGM 218 and A. Servov, H.Amidov, PGM. sapphire, P. Thermov-PGM for oxygen reduction" patterned bimetallic Non-PGM catalyst for oxygen reduction "PGM 80 (PGM) 213 PGM and A. sapphire, H.56-amine catalyst and high activity of C. amine, N. carbide, P. Robson, P. Amarassov, R. C, N. C. D.P.S.S. App. Aplatasol, P. Adelyassov., incorporated herein by reference, respectively). The Fe-CBDZ catalyst series was prepared using a heat treatment temperature variation of 750 ℃ and 900 ℃ (FIG. 11). It was found that the catalyst prepared at T =800 ℃ had the highest ORR activity. The lowest activity was observed for Fe-CBDZ treated at T =750 ℃, although the amount of nitrogen was the highest at this temperature (fig. 9), but clearly this temperature was sufficient to form active sites. However, we have previously shown that too high pyrolysis temperatures lead to a reduction in activity due to Active site decomposition (see, e.g., a. Serov, m.h. Robson, k. artyuhkova, p. ataassov "Templated Non-PGM Catalysts Derived from Iron and poly (ethyleneimine) precursors) application. cat. B127 (2012) 300-306 and a. Serov, m.h. Robson, B. Halevi, k. artyuhkova, p. ataassov" high activity and durably tested Non-PGM Catalysts Derived from Iron and amino substituted Catalysts "7. h. rob. c. h. c. B. c. h. r. c. h. c. and B. c. B. c. f. h. B. h. r. robasc. B. c. B. h. c. h. c.

In the inert (N)₂) And reactivity (NH)₃) The effect of the second treatment in two different atmospheres on ORR activity is shown in figure 12. Although similar limiting currents were found for the single-treated and double-treated materials, it can be seen that the greatest increase in kinetic activity was found when the second heat treatment was carried out in a reactive atmosphere. From this data, it can be assumed that the second treatment in ammonia increases with Fe-N₄The amount of active center involved.

An in-depth analysis of the correlation between the surface chemistry (XPS data) and the properties (RRDE, E1/2) of the material was then carried out. The results are shown in fig. 13 and 14. In the attached drawings, p-pyridine nitrogen and Fe-N₄The absolute amount of the species is plotted as a function of the half-wave potential (half-wave potential) E1/2. The samples pyrolyzed at different temperatures and with different precursor ratios had a measured E1/2 in the range of 0.72-0.79V. The best activity was observed for the Fe-CBDZ sample pyrolyzed at 800 ℃. It is clearly marked that as the amount of pyridine nitrogen increases, a higher electrocatalytic activity for oxygen reduction is expected, which is in full agreement with published data. However, although the metal-free sample pyrolyzed under the same conditions and had significant pyridine nitrogen content, the metal-free sample showed significantly lower activity (E1/2= 0.40V). This can be explained by the assumption that the pyridine nitrogen center only works in the first 2 e-step, which is due to the high H in the iron-free sample₂O₂And (5) output certification. Among Fe-containing materials, Fe-6CBDZ, Fe-10CBDZ and Fe-12CBDZ has a greater amount of pyridine nitrogen of 10-30%. However, their activity is 5% less than the best performing Fe-8 CBDZ. In addition, Fe-8CBDZ has the largest amount of Fe-N₄Center (fig. 15). Fe bound to N, especially with Fe-N₄The presence of configuration is crucial, as shown by the strong correlation (R2=0.9), fig. 14). The correlation analysis between the surface fraction and the ORR properties showed, without doubt, that Fe-N₄Is an inherent active site for oxygen reduction in a large number of Fe-N-C type catalysts.

The RDE-based durability tests were performed under DoE recommended conditions for non-PGM cathode catalysts. It was found that Fe-8CBDZ is an extremely durable catalyst with an activity loss of only 6% after 10000 cycles (FIG. 16). An unusual increase in performance between 5000 and 10000 cycles was observed. This unusual increase can be explained by improved accessibility of the active site to oxygen, most likely due to increased hydrophilicity during cycling.

The RRDE data show that Fe-8CBDZ is a very promising platinum replacement material. To demonstrate this, MEA tests were performed on both single heat treated and double heat treated samples (fig. 17). The performance trends are the same as in the RRDE test: fe-8CBDZ-DHT- Ν h 3> > Fe-8CBDZ-DHT-N2> Fe-8 CBDZ-SHT. The highest activity at 0.6V was found to be 0.7A cm-2, 40% of the platinum performance. Considering the low cost of making Fe-CBDZ catalysts and the high activity and durability of this material, it can be considered as a true candidate for replacing platinum in oxygen reduction reactions.

Claims (18)

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

providing sacrificial template particles;

reacting a metal precursor and befenati onto the sacrificial template particles to produce a dispersed precursor;

heat treating the dispersed precursor; and

removing the sacrificial template particles to produce a self-supporting electrocatalytic material.

2. The method of claim 1, wherein the metal precursor is a transition metal precursor.

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

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

5. The process of claim 4, wherein the pyrolysis is carried out at a temperature of from 500 ℃ to 1100 ℃.

6. The process of claim 4, wherein the pyrolysis is conducted in a reactive atmosphere selected from ammonia or acetonitrile.

7. The process of claim 6, wherein the pyrolysis is carried out in ammonia.

8. A catalytic material comprising a metal and carbon, wherein greater than 75% of the carbon is derived from befenate.

9. The catalytic material of claim 8, wherein the catalytic material is unsupported.

10. The catalytic material of claim 9, wherein all of the carbons in the material are derived from befenate.

11. The catalytic material of claim 8, wherein the metal is a transition metal.

12. A catalytic material formed by:

providing sacrificial template particles;

reacting a metal precursor and befenati onto the sacrificial template particles to produce a dispersed precursor;

heat treating the dispersed precursor; and

removing the sacrificial template particles to produce a self-supporting electrocatalytic material.

13. Catalytic material according to claim 12, wherein the dispersed precursor is heat treated by pyrolysis.

14. The catalytic material of claim 12, wherein the metal precursor is a transition metal precursor.

15. The catalytic material of claim 14, wherein the metal precursor is ferric nitrate.

16. Catalytic material according to claim 13, wherein the pyrolysis is carried out at a temperature of 500 ℃ to 1100 ℃.

17. Catalytic material according to claim 16, wherein the pyrolysis is carried out in a reactive atmosphere selected from ammonia or acetonitrile.

18. Catalytic material according to claim 17, wherein the pyrolysis is carried out in ammonia.