JPS6140459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in supported catalysts. The present invention relates to an improved process for making a supported catalyst and an improved supported catalyst made by the process. Particular supported catalytic materials relevant to the present invention are those that include a catalytic metal in the form of a surface layer on a carbon-containing support material, most particularly supported catalyst materials useful as electrodes such as fuel cells. It is a noble metal catalyst.

Elemental carbon is obtained in two different allotropic forms, as diamond and as graphite. In diamond, the individual carbon atoms are arranged in a tetrahedral manner and at an equidistant distance of 1.54 Å. It is covalently bonded by electron pairs occupying confined molecular orbitals formed by overlapping sp ³ hybrids. This structure gives the crystal great hardness, but allows four well-defined cleavages. In graphite, carbon atoms form plate-like layers in which widely arranged atoms form a mesh of six-membered carbon rings with a carbon-carbon distance of 1.42 Å. All carbon atoms in the layer are
It is attached to the other three carbon atoms in the layer by covalent bonds equivalent to confined molecular orbitals created by overlapping sp ² hybrids with two electrons each. Electrons in the unhybridized p orbitals form a mobile metallic system. The layers are held together by weak van der Waals forces and the interplanar distance is variable and increases as the area of the sheets within the crystal decreases.
Graphite is actually the most stable allotrope of carbon, and diamond can be easily converted to graphite by the action of heat. All forms of carbon other than diamond have graphite properties. The varying properties and apparently amorphous nature of charcoal, for example, result from variations in the size of the unit crystallites and the degree to which they are arranged within the grain. Thermal decomposition of short-chain hydrocarbon vapors such as methane produces polycrystalline materials that are gas impermeable, much stronger than regular graphite, and highly anisotropic in their thermal and electrical conductivity. A dense layer of is formed on the heated substrate. The conductivity in the a-axis can be greater than copper, while in the c-axis it can be 100 times lower. This material is known as pyrolytic graphite or pyrographite. Carbon fibers are polycrystalline in nature and consist of a large number of small, closely packed cylindrical crystallites, each with about 30 layers of faces and about a diameter.
250 Å and has an unknown, even longer length, called a fibril. They have planes of parallel layers clustered together with larger interlayer spacings than in massive graphite crystals, and atoms in the planes of the layers are distinct from other atoms in the parallel planes as in massive graphite crystals. has no interval relationship. This structure is turbostrategic.
It is said that

The present invention provides a method for preparing an improved supported catalyst by subjecting a carbon-containing support material to an oxidative treatment, contacting the treated support material with a metal-containing solution and drying the support material in the form of polycrystalline graphite. a solution containing at least a portion of carbon; producing acidic or alkaline oxide groups on the polycrystalline graphite by surface oxidation; impregnating or alkaline surface oxidized support material with a solution containing the anion of the catalytic metal to form a salt therewith, and drying and reducing the impregnated support material to deposit the catalytic metal on its surface. Provided is a manufacturing method characterized by forming a layer of.

Impregnation of a carbon-containing support material with a catalytic metal salt solution, followed by drying and reduction of the salt, is a known method for preparing noble metal catalysts supported on carbon.
However, it is not specified that the carbon-containing materials conventionally disclosed as carriers should be at least in the form of polycrystalline graphite, nor are these materials subjected to any form of surface oxidation treatment. Never before. Furthermore, the solution preferably used to impregnate the support material is selected to contain ions of the catalytic metal in a suitable form to generate a metal salt which can be subsequently reduced to the catalytic metal by reaction with the oxidized surface. Never before.

Now, using the method according to the invention, ionic oxide groups are created on the surface of the carbon microcrystals of polycrystalline graphite during the oxidation step, and then upon impregnation with a solution of the corresponding salt containing metal ions of opposite charge. It is believed that these metal ions react with the ionic oxide groups, chemically bond to the surface, and are widely distributed on the surface. The presence of such charged groups on the carbon surface also appears to enhance the effectiveness of the catalytic metal. It is believed that subsequent drying and reduction causes the metal to become directly bonded onto the carbon surface at the initial bonding site.

Experiments have shown that using the same carbon-containing support and the same catalytic metal but not using the method of the present invention does not result in materials as useful as those obtained using the improved method of the present invention. Shown.

Support materials suitable for use in the present invention include at least a proportion of carbon in the form of polycrystalline graphite which can be utilized for oxidation.
It can be any material that can be used as a support for supported catalysts. The polycrystalline graphite can be structurally incorporated into the carrier material or can be present in the form of a binder or surface layer converted into the desired shape. Suitable carrier materials are:
Carbon fibers obtained from rayon precursors, such as those produced by Union Carbide, may have a particularly high content of polycrystalline graphite and can be effectively processed in the form of matte or paper. Carbon fiber mats may be used in paper, or they may be obtained from other materials having a lower polycrystalline graphite content and containing a binder converted into polycrystalline graphite form. It's okay to be hot. Any of the above types of carbon fiber materials may be further modified by the addition of suitable filler materials which can subsequently be converted into the form of polycrystalline graphite. Examples of suitable filler materials include coal tar or petroleum pitch, ethylene cracker residue, and polyphenylene or various Epikote resins. A suitable filler material for carbon fiber paper is polyvinylidene chloride, commercially available as Saran powder, which can be pressed into the surface of the carbon fiber paper and then calcined and heated. Decomposed to yield a filled material with virtually no macropores, a very large surface area, a very high polycrystalline graphite content, and particularly suitable as a substrate for liquid or gas diffusion electrodes. .

The surface oxidation of the carbon-containing support material to produce acidic oxide groups is preferably carried out by, for example, electrochemical oxidation, e.g. anodic oxidation in sulfuric acid (Electrochemical Oxidation, N.
L. Weinburg and Reddy, Journal of
Applied Electrochemistry (Journal of
Applied Electrochemistry, Volume 3, Page 73 (1973)], by ion bombardment in the presence of gaseous oxygen, or by treatment with concentrated acids or mixtures of concentrated nitric acid and potassium dichromate. Performed by chemical oxidation.

Similarly, although any of the methods known for producing basic oxide groups on polycrystalline graphite carbon surfaces can be used, one method that the inventors have found to be most suitable is to The method involves heating to an elevated temperature (eg 900°C) in a nitrogen atmosphere, then cooling to room temperature and exposure to oxygen.

Catalytic metals most suitable for use in the present invention include platinum group metals, commonly referred to as noble metals. These include the group metals of the periodic table, namely platinum, palladium, rhodium, osmium, iridium and ruthenium, which may be used alone or in combinations of two or more. Other catalytic metals, such as metals from groups a and b of the periodic table, ie tin, lead, germanium or titanium, may also be used to enhance the action of the noble metals.

Impregnation of the oxidized polycrystalline graphite-containing support material is carried out using a dilute solution of a salt containing the appropriate cation or anion of a suitable metal. Suitable solutions containing metal cations for use in polycrystalline graphite materials having acidic oxide groups on the surface include, for example, platinum tetramine hydroxide Pt(NH ₃ ) ₄ (OH) ₂ to yield platinum metal catalysts. Aqueous solution, platinum tetramine chloride Pt (NH ₃ ) ₄ Cl ₂ aqueous solution, platinum diamine dinitrate Pt (NH ₃ ) ₂
Concentrated nitric acid solution of (NO ₂ ) ₂ or platinum diamine dinitrate and ruthenium nitrosyl nitrate RuNO (NO ₃ ) ₂ or ruthenium nitrate Ru to produce a mixed platinum metal/ruthenium metal catalyst.
(NO ₃ ) ₃ in concentrated nitric acid solution.

Similarly, the impregnation of polycrystalline graphite with basic oxide groups on the surface can be carried out using any dilute solution of salts containing anions of suitable metals, and the inventors have demonstrated the ability to produce platinum-containing catalysts. We have found chloroplatinic acid H ₂ PtOCl ₆ to be particularly useful for this purpose.

After impregnation, the support material is dried at a suitable temperature, for example 120° C., and the salt on the support material decomposes into the catalytic metal. The conditions under which the cracking is carried out affect the activity of the resulting catalyst. For monometallic platinum catalysts, the preferred method is to heat the dry impregnated support in air at 200°C.
It turned out that the method involves heating at a temperature of -500°C. A temperature of 300°C is particularly suitable. Alternatively, the support can be heated in a nitrogen atmosphere to a temperature of 200°C to 500°C, in particular to a temperature of 400°C. Heating can also be carried out in a hydrogen gas atmosphere at the same temperature, but under these conditions agglomeration of the metal occurs and a less active catalyst is obtained. For secondary metal catalysts, such as platinum/ruthenium catalysts, the most preferred method is the same as for single metal catalysts, which is heating in air to 200°C-500°C, especially 300°C. Heating in nitrogen atmosphere is 200℃-500℃
It can be carried out preferably at 300°C. Using a hydrogen gas atmosphere at the same temperature results in a less active catalyst than any of the other methods, which is due to the platinum enrichment of the secondary metal material on the support surface.

The invention will be further explained with reference to examples comparing catalyst materials produced according to the invention with catalyst materials obtained using other methods outside the scope of the invention. The usefulness of the method for producing a supported catalyst material of the present invention and the usefulness of the catalyst produced by the method, particularly as a catalyst for methanol electrooxidation reaction, will be understood by comparing various materials.

Various supported catalysts were prepared using the following method.

Example A (a) Platinum diamine dinitrate Pt(NH ₃ ) ₂ (NO ₂ ) ₂ and ruthenium nitrosyl nitrate RuNO(NO ₃ ) ₂ at 30% on a sheet of unfilled carbon fiber paper without an oxidation step. The solution in nitric acid was impregnated and dried at 120°C, and the salt was decomposed at 400°C for 2 hours in flowing nitrogen.
The final reduction was carried out under hydrogen at 400°C or electrochemically in trisulfuric acid.

(b) Another piece of unfilled carbon fiber paper was oxidized in concentrated nitric acid at 100°C for 2 hours, then impregnated with the same solution, dried at 120°C, and the salt was heated to 400°C in flowing nitrogen. and allowed to decompose for 2 hours. The final reduction was carried out under hydrogen at 400°C or electrochemically in trisulfuric acid.

Example B Several sheets of the unfilled carbon fiber paper described above were impregnated with pitch (i.e., using ethylene cracker residue) at room temperature and heated to 800° C. through a planned cycle in a nitrogen atmosphere. Several sheets of pitch-impregnated material were then graphitized by heating to a temperature of 1000°C-2500°C for 30 minutes. After graphitization of the filler, it was oxidized by treatment in concentrated nitric acid at 100 DEG C. for 1 to 20 hours to form acidic oxide groups on the surface. After oxidation, the following noble metal salts were impregnated.

(a) Pt(NH ₃ ) ₂ (NO ₂ ) ₂ aqueous solution; (b) Pt(NH ₃ ) ₄ Cl ₂ aqueous solution; (c) H ₂ PtCl ₆ aqueous solution; (d) Pt(NH ₃ ) ₄ Cl ₂ +SnCl ₄ aqueous solution; (e) H ₂ PtCl ₆ +SnCl ₄ aqueous solution: (f) PtCl ₄ +SnCl ₄ aqueous solution; (g) Pt(NH ₃ ) ₂ (NO ₂ ) ₂ + RuNO(NO ₃ ) ₂ 30% solution in nitric acid; ( h) H ₂ PtCl ₆ + RuCl ₃ aqueous solution.

It was then dried at 120°C and the salt was decomposed in flowing nitrogen at 400°C for 2 hours.

Example C An additional sheet of unfilled carbon fiber paper was heated to 900° C. for 2 hours in a drying chamber, then cooled to room temperature still in a dry nitrogen atmosphere, and then exposed to air. The support was then impregnated with a chloroplatinic acid solution, dried at 120°C and the salt decomposed at 400°C in flowing nitrogen.

In all the above cases the final reduction was carried out electrochemically in hydrogen at 400°C or in 3 molar sulfuric acid.

Example D Several sheets of unfilled carbon fiber paper are filled by pressing Saran powder (300-400 mesh) onto the surface using a pressure of 30 Kg/ ^cm2 , and the powder is heated to 200°C.
and the process was repeated. The filled carbon fiber paper was graphitized by heating at 950 °C for 1 h under nitrogen, and after graphitization at 100 °C with a potassium dichromate (K ₂ Cr ₂ O ₇ )/nitric acid mixture.
Oxidized for 0.5-20 hours and washed. Platinum is added to the activated support in anionic form by impregnation with an aqueous solution of H ₂ PtCl ₆ or in cationic form by impregnation with an acidic solution of Pt(NH ₃ ) ₂ (NO ₂ ) ₂ . was added and after drying the salt was decomposed in flowing nitrogen (hydrogen or air) for 2 hours at 400°C.

Example E A similar unfilled carbon fiber paper was filled with:

(a) polyphenylene resins that yield graphitizable carbon upon carbonization; and (b) bakelite resins that yield non-graphitizable carbon.

Bakelite resin was employed as a saturated solution of powder in methyl ethyl ketone.

The polyphenylene prepolymer, curing agent and catalyst were all dissolved in chloroform and the paper soaked and dried. The filled paper in both cases was heated to 800 °C in a nitrogen atmosphere through a planned cycle and then heated with nitric acid at 100 °C.
Treated for 20 hours. Pt on the paper after the treatment
(NH ₃ ) ₂ (NO ₂ ) ₂ impregnated with concentrated nitric acid solution and heated at 120℃.
and activated in nitrogen at 400° C. for 2 hours.

Example F A sample of pure amorphous carbon of the type used as a support in the production of industrial supported catalysts was heated to 100°C.
Pt was treated in concentrated nitric acid for 1 to 20 hours.
It was impregnated with an acidic solution of (NH ₃ ) ₂ (NO ₂ ) ₂ , dried at 120° C. and the salt was decomposed at 400° C. in flowing nitrogen for 2 hours. The final reduction was carried out in hydrogen at 400°C,
or electrochemically in sulfuric acid.

Example G A sample of the most commercially available supported catalyst suitable for use in methanol electrooxidation reactions was obtained for comparison. The following were selected:

(a) Platinum Adams catalyst; (b) Platinum/Ruthenium Adams catalyst; (c) Pore-activated [Engelhard] platinum catalyst on carbon; (d) Electroplated onto an inert support. (e) platinum/tin/electroplated on an inert support;
lead.

The unfilled carbon fiber paper used in all of the processes described in A, B, C, D, and E is a pyrographite-coated carbon fiber material manufactured by Union Carbide, and thus has a certain proportion of polycrystalline 1 is an example of a carrier material comprising graphite and according to the invention. The amorphous carbon used in the process according to point F does not contain any polycrystalline graphite, so it is not a support material according to the invention and likewise the industrially available catalyst according to point G. The carrier used in the process does not contain polycrystalline graphite material and is therefore outside the scope of the present invention.

The process described in Example A(a) uses a support material according to the invention, but omits the oxidation of the surface before impregnation with the solution of the noble metal salt. The preparation of Example A(b) is similar, but the entire method of the invention is used;
The surface is then oxidized with concentrated nitric acid to generate acidic oxide groups prior to solution impregnation. When tested for activity in the methanol electrooxidation reaction, the first material has some efficacy due to the presence of platinum and ruthenium metals on its surface, but the second material has significantly improved activity and surface oxidation. is shown to be a necessary step in the method of the invention.

The process described in Example B uses the same carrier material as described in Example A and fills the carrier material with pitches that form a polycrystalline graphite material when carbonized. After filling, the carrier material and its filler are
It was oxidized for various times and showed the effect of its oxidation to produce acidic groups. After the oxidation step, the support material is impregnated with certain noble metal salts, some of which are cationic and therefore reactive with acidic groups according to the invention, some of which are anionic and therefore reactive with acidic groups. even less reactive.

When the activity of the various catalysts formed was determined for the methanol electrooxidation reaction, it was found that by increasing the intensity of the oxidation step, i.e. increasing the contact time with concentrated nitric acid,
The suitability of the catalysts produced increases, but under selected conditions it is possible to determine the optimum time, which is up to about 20 hours, and any increase in time beyond this time will result in significant No effect was obtained.

Furthermore, in the case of the supports used in this example and having acidic oxide groups on the surface, the anionic solutions used, namely H ₂ PtCl ₆ and H ₂ PtCl ₆ +RuCl ₃
is a solution containing catalytic metal cations e.g. 30%
Pt(NH ₃ ) ₂ (NO ₂ ) + RuNO dissolved in HNO ₃
This resulted in a final product that was much inferior to that produced using a solution of ( _NO3 ) ₂ . The best platinum/tin/catalyst produced was with an aqueous solution of Pt(NH ₃ ) ₄ Cl ₄ , the next best was
It uses an aqueous solution of H ₂ PtCl ₆ +SnCl ₄ .

Example C describes a method of preparing a support material having basic oxide groups on its surface and then impregnating it with a solution containing an anion of the catalytic metal to decompose the salt formed.

The process described in Example D is a process using Saran powder as a filler according to the invention. Different oxidation times were used and different noble metal solutions were used to impregnate the loaded support. Again, the determination of the catalytic activity in the methanol electrooxidation reaction shows that it is important to carry out the oxidation step before impregnation and that it is optimal when the support material used has acidic oxide groups. It has been shown that it is important to use cationic salt solutions to obtain results. Catalysts prepared using solutions of Pt( _NH3 ) ₂ ( _NO2 ) ₂ or Pt( _NH3 ) ₄ (OH) ₂ are much more active than those obtained using solutions _{of H2PtCl6} . It was active. It was also found that the carbon filling obtained using Saran powder was very homogeneous and free of pinholes. Blow-out (in water) of filled carriers
Pressures were also measured to demonstrate that they are effective for use as liquid or gas diffusion electrodes, particularly as fully carbon-based substrates suitable for use in high temperature methanol vapor electrodes or air electrodes. found.

The process described in Example E shows the effect of adding a material that produces polycrystalline graphite upon carbonization compared to the addition of a material that does not.

In contrast to the highly active catalyst obtained from polyphenylene-filled paper, the catalyst based on Bakelite-filled substrate showed slightly higher activity after oxidation and impregnation with noble metal cation solution than the untreated substrate itself.

The catalyst prepared according to the method described in Example F is
It showed an activity equal to that of the materials listed in Example G as examples of commercially available catalysts. The substrate used did not contain any polycrystalline graphite, so treatment with concentrated nitric acid had no appreciable beneficial effect.

The various catalysts described above that were evaluated in methanol electrooxidation reactions prepared according to the method of the present invention all exhibited improved activity and utility over the commercially available catalysts listed in Example G. Ta.

The following more specific examples provide a more direct individual comparison of electrodes produced using the catalyst of the invention with those according to the prior art, and illustrate the importance of the various steps of the process of the invention. This shows that.

Example H (a) A sheet of unfilled pyrographite-coated carbon fiber paper is treated with platinum tetramine hydroxide, Pt(NH ₃ ) ₄ without any special pretreatment steps.
(OH) ₂ or an aqueous solution of platinum diamine dinitrate (5 mgPt/ml) was heated with an infrared lamp (substrate temperature 150
℃). A platinum charge of 0.35 mg/cm ² was obtained. The impregnated catalyst was activated at 400° C. for 1 hour in a nitrogen atmosphere. methanol 1
The activity at 60° C. in sulfuric acid 3 containing 10 A/g at 0.52 V with respect to the bubbling hydrogen electrode. Commercially available catalysts under the same conditions
It had an activity of 20A/g at 0.52V.

(b) A sheet of unfilled pyrographite-coated carbon fiber paper is exposed to a 30% nitric acid solution containing 5 mg/ml of platinum while being heated under an infrared lamp (substrate temperature 150°C) without any special pretreatment steps. It was simply impregnated with a solution of platinum diamine dinitrate. A platinum charge of 0.4 mg/cm ² was obtained. The impregnated catalyst was activated at 400° C. for 1 hour in a nitrogen atmosphere. The activity at 60° C. in sulfuric acid electrolyte 3 containing 1 methanol was 20 A/g at 0.47 V associated with a bubbling hydrogen electrode. The commercially available Pt Adams catalyst had an activity of 20 A/g at 0.52 V under the same conditions.

(c) A similar unfilled pyrographite-coated carbon fiber paper was treated with a solution of 40 g concentrated nitric acid, 5 g potassium dichromate and 6 g water at 70° C. for 2 hours. The oxidized paper was washed with distilled water until free of dichromate ions and then dried at 120°C. Impregnation was carried out using a 30% solution of platinum diamine dinitrate in nitric acid containing 5 mg/ml of cationic platinum. A platinum charge of 0.4 mg/cm ² was obtained. The impregnated material was dried at 120°C and then activated for 1 hour at 400°C in a nitrogen atmosphere. The activity at 80℃ in sulfuric acid electrolyte 3 containing 1 methanol is
It was 20A/g at 0.42V. The commercially available Pt Adams catalyst is 20 at 0.48V under the same conditions.
It had an activity of A/g.

(d) A sheet of unfilled pyrographite coated carbon fiber paper as described above was treated with the acid/dichromate solution described above at 70°C for 2 hours, washed and dried at 120°C. Impregnation was carried out with an aqueous solution of platinum tetramine hydroxide (5 mg Pt/ml). 0.1mg/ ^cm2
A platinum charge of . The impregnated material was dried at 120°C and then activated in air at 300°C for 1 hour. An activity of 20A/g was obtained at 60℃ at 0.48V,
On the other hand, the commercially available Pt Adams catalyst exhibited an activity of 20 A/g at 0.52 V under the same conditions.

(e) An additional piece of unfilled pyrographite-coated carbon fiber paper is treated with an acidic aqueous solution of platinum diamine dinitrate and ruthenium nitrate (70% by weight) without subjecting it to a separate pretreatment step.
Impregnated with Pt30wt% Ru5mg/ml), 0.45mg/
A metal charge of cm ² was obtained. The impregnated catalyst was dried at 120°C and then activated in air at 300°C for 1 hour.
An activity of 100A/g was obtained at 60°C and 0.4V. The industrial Pt/Ru Adams catalyst under the same conditions
It had an activity of 100A/g at 0.51V.

(f) A third unfilled pyrographite-coated carbon fiber paper was subjected to electrochemical oxidation as an anode in an electrolytic cell at 25°C against a carbon rod cathode using a trisulfuric acid electrolyte at a standard current density for 30 min. 10m
A/electrode surface cm ² was used. The oxidized paper was impregnated, washed, dried and activated as described above to obtain a platinum loading of 0.5 mg/cm ² . An activity of 10A/g was obtained at 0.42V at 80℃,
Industrial Pt Adams catalyst is 0.45V under the same conditions
showed an activity of 10A/g.

(g) A fourth identical unfilled carbon fiber paper was oxidized as in Example H(c) above and then anionic platinum 5
It was impregnated with an aqueous solution of chloroplatinic acid (H ₂ PtCl ₆ 6H ₂ O) containing mg/ml. A platinum charge of 0.7 mg/cm ² was obtained. The impregnated material was dried at 120°C and activated at 400°C in a nitrogen atmosphere. 20 at 0.57V at 60℃
An activity of A/g was obtained, while the commercially available Pt Adams catalyst showed an activity of 20 A/g at 0.52 V under the same conditions.

(h) A fifth unfilled pyrographite-coated carbon fiber paper was heated at 900° C. for 5 hours in a nitrogen atmosphere and cooled to room temperature in the same atmosphere. The substrate was then exposed to oxygen at room temperature. Impregnation was carried out using an aqueous solution of chloroplatinic acid containing 5 mg/ml of anionic platinum. A platinum charge of 0.9 mg/cm ² was obtained. The impregnated paper was then dried at 120°C and activated for 1 hour at 400°C in a nitrogen atmosphere. At 60℃
An activity of 20A/g was obtained at 0.50V.

(i) 6th similar carbon fiber paper with concentrated nitric acid 40%
g, 5 g of potassium dichromate and 6 g of water at 70°C for 2 hours, then washed and dried at 120°C. This substrate was then coated with a solution of platinum diamine dinitrate Pt(NH ₃ ) ₂ (NO ₂ ) ₂ and ruthenium nitrosyl nitrate RuNO(NO ₃ ) ₂ in 50% nitric acid solution (metal ratio: 80% by weight platinum, ruthenium 20% by weight), dried at 120°C and then activated at 400°C in a nitrogen atmosphere. The activity of the obtained catalyst was 50 A/g at 0.36 V at 80° C., and a commercially available platinum/ruthenium catalyst with a similar composition showed an activity of 50 A/g at 0.45 V.

(j) Another sheet of carbon fiber paper was subjected to ion bombardment treatment for 2 hours at a pressure of 0.2 mmHg and a current of 0.5 A. This substrate was then impregnated with the platinum/ruthenium solution described above, dried and activated.
An activity of 50 A/g was obtained at 0.36 V at 80°C.

(k) Commercially available activated carbon powder was diluted with concentrated nitric acid at 100℃ for 48 hours.
It was treated for some time, washed and dried. The substrate was then impregnated with an acidic aqueous solution of platinum diamine dinitrate to obtain a platinum loading of 0.5 mg/cm ² , dried at 120°C and activated at 400°C in a nitrogen atmosphere. This catalyst had an activity of 20 A/g at 0.55 V at 80°C, which was inferior to commercially available catalysts.

(l) The acid treated substrate as described above was impregnated with the platinum/ruthenium solution described above, dried at 120°C and then activated in nitrogen at 400°C. 80℃
The activity was 50A/g at 0.40V.

(m) A sheet of unfilled pyrographite-coated carbon fiber paper is heated to 200°C.
(topped) immersed in ethylene cracker residue;
Drained and dried. The fill material was then carbonized in an 8 hour temperature programmed cycle that included a gradual temperature increase from 300°C under nitrogen and a final heat treatment at 1500°C for 0.5 hour in an argon atmosphere. After filling and carbonizing the paper, it was treated with concentrated nitric acid at 80°C for 72 hours, then washed,
It was dried at 120°C. Impregnation was carried out using an acidic aqueous solution of platinum diamine dinitrate at 1 mg/cm ²
A platinum charge of . The catalyst was then dried at 120°C and activated at 400°C in a nitrogen atmosphere. 80
The activity obtained at °C was 20A/g at 0.44V.

(n) An additional sheet of unfilled carbon fiber paper is similarly filled with ethylene cracker residue, then carbonized and oxidized, and then impregnated with a solution containing platinum diamine dinitrate and ruthenium nitrosyl nitrate. A metal charge of 1 mg/cm ² was obtained, dried and activated. The activity at 80°C was 50A/g at 0.35V.

(o) Furthermore, the surface of a sheet of unfilled carbon fiber paper was pressed and filled with dry powder (300-400 mesh) at a pressure of 30 g/cm ² . The product was calcined at 200°C and the process was repeated. The filled carbon paper was graphitized by heating under a nitrogen atmosphere for 1 hour and then treated with nitric acid, potassium dichromate solution at 70° C. for 3 hours to generate acidic oxide groups. Impregnation was carried out using aqueous platinum tetramine hydroxide [Pt(NH ₃ ) ₄ (OH) ₂ ] to remove platinum.
Obtain a metal loading of 0.1mg/ ^cm2 and then heat the catalyst to 120℃
and activated at 300°C in air. An activity of 60 A/g at 0.50 V at 60° C. was obtained, which was superior to the activity of commercially available catalysts under the same conditions.

These examples show that:

(i) Comparing Examples H(a), (b) and (c), a cation-containing solution of a catalytic metal is applied to a polycrystalline graphite-containing support material in the presence and absence of acidic oxide groups. The effect of impregnation is shown. In (a) no acidic oxide groups are formed. In (c) an acid pretreatment of the substrate is carried out to generate acidic oxide groups before impregnation, and in (b) acidic oxides are formed by the action of the acid used as a solvent for the catalytic metal solution. groups are generated on the spot.

(ii) Example H(d) illustrates this feature. This is because in this case the substrate is pretreated with acid to produce acidic oxide groups, but the impregnating solution used itself is acid-free.

(iii) Example H(e) shows the preparation of a mixed metal catalyst according to the invention. The substrate is pretreated with acid and the solution used for impregnation is an acidic solution. The obtained catalyst is of very good quality.

(iv) Example H(f) shows an alternative method of generating acidic oxide groups using electrochemical oxidation. The catalysts obtained are equivalent to those obtained by chemical oxidation H(b), (c) and (d), and all without producing acidic oxide groups on the polycrystalline graphite substrate. Significantly better than the manufactured one.

(v) Example H(g) is a method of applying catalytic metals to a polycrystalline graphite-containing support that has been oxidized to form acidic oxide groups on the surface of the polycrystalline graphite, contrary to the requirements of the present invention. Figure 2 shows an attempt to produce a catalyst by impregnating a solution containing anions. The catalysts obtained were prepared using polycrystalline graphite-free support materials [Examples H(f), (k) and
(l)] is inferior to that obtained by impregnation.

Example H(h) shows a similar support material that has been oxidized in a manner that produces basic oxide groups on the polycrystalline graphite surface and then impregnated with the same anion-containing solution. This process according to the invention yields useful catalysts.

(vi) Examples H(i) and (j) illustrate the preparation of bimetallic electrodes according to the method of the invention, producing acidic oxide groups on the support and forming a solution containing cations of both these and the metal of interest. Two different ways of reacting are shown. The resulting catalyst was superior to commercially available carbon-supported bimetallic catalysts.

(vii) The activated carbon powder used as support material in Examples H(k) and (e) did not contain polycrystalline graphite and was subjected to subsequent oxidation with concentrated nitric acid and cation-containing solutions of the catalytic metals. By impregnation, the industrially available Only a catalyst with the same tactility was formed.

(viii) Examples H(m), (n) and (o) demonstrate the utility of materials convertible to polycrystalline graphite as fillers for porous supports resulting in the utility of catalysts formed. show. Such filling is likely necessary to change the physical properties of the electrode being formed. These examples demonstrate that the presence of polycrystalline graphite in the filler does indeed tend to enhance the activity of the resulting catalyst.

Claims (1)

Claims: 1. An improved method for preparing a supported catalyst by subjecting a carbon-containing support material to an oxidative treatment, contacting the treated support material with a metal-containing solution, and drying the support material, wherein the support material is polycrystalline graphite. producing acidic or alkaline oxide groups on the polycrystalline graphite by surface oxidation; containing cations of the catalytic metal in the acidic surface oxidized support material; impregnating the alkaline surface-oxidized support material with a solution containing an anion of the catalytic metal to form a salt therewith;
and drying and reducing the impregnated carrier material to form a layer of catalytic metal on its surface. 2. The method of claim 1, wherein the polycrystalline graphite is structurally incorporated into the carrier material. 3. Process according to claim 1, in which polycrystalline graphite is incorporated into the carrier material as a binder that binds the carrier material. 4. Process according to claim 1, in which polycrystalline graphite is incorporated into the carrier material as a filler. 5. Process according to claim 1, wherein the polycrystalline graphite is incorporated into the carrier material as a surface layer. 6. The manufacturing method according to any one of claims 1 to 5, wherein the carrier material contains carbon fibers. 7. The manufacturing method according to claim 6, wherein the carbon fiber is in the form of a pine. 8. The manufacturing method according to claim 6, wherein the carbon fiber is in the form of paper. 9 Claim 4, wherein the filler is pitch
Manufacturing method described in section. 10. The manufacturing method according to claim 4, wherein the filler is ethylene cracker residue. 11. The manufacturing method according to claim 4, wherein the filler is polyphenylene. 12 The filler is polyvinylidene chloride,
The manufacturing method according to claim 4. 13. The manufacturing method according to claim 4, wherein the filler is an epoxy resin composition. 14 Claim 1-1, in which acidic oxides are produced on polycrystalline graphite by surface oxidation
The manufacturing method described in any of Item 3. 15 Claim 1-- in which a basic oxide is formed on the polycrystalline graphite by surface oxidation.
The manufacturing method according to any one of Item 13. 16. The manufacturing method according to claim 14, wherein the surface oxidation is electrochemical oxidation. 17. The manufacturing method according to claim 14, wherein the surface oxidation is chemical oxidation. 18. The manufacturing method according to claim 14, wherein the surface oxidation is an ion bombardment treatment. 19. Claim 15, wherein the basic oxide groups are formed by heating the polycrystalline graphite-containing support material to an elevated temperature in a nitrogen atmosphere and then exposing it to oxygen at room temperature. Manufacturing method described in section. 20. A process according to any of claims 1-19, wherein the catalytic metal is a noble metal or a combination of such metals. 21. The method of claim 20, wherein the method is present with a metal or a noble metal or a combination of noble metals selected from metals of groups a or b of the periodic table of the elements. 22. The method of any of claims 1-14, 16-18, or 20-21, wherein the impregnating solution contains an anion of a catalytic metal. 23 Claims 1-13, 15 or 1, wherein the impregnating solution contains cations of the catalytic metal
The manufacturing method according to any one of Items 9-21. 24. A process according to any of claims 1 to 23, wherein the impregnated carrier material is heated in air to a temperature of 200°C to 500°C to partition the catalytic metal salts on the material. 25 Claim 2 in which the temperature is 300°C
The manufacturing method described in Section 4. 26. A process according to any of claims 1-23, wherein the impregnated support material is heated in nitrogen to a temperature of 200C to 550C to decompose the catalytic metal salt on the material. 27 Claim 2 where the temperature is 400°C
The manufacturing method described in Section 6. 28. A process according to any of claims 1-23, wherein the impregnated carrier material is heated in hydrogen to a temperature of 200C to 500C to decompose the metal salts on the material. 29. A process according to any of claims 24-28, wherein the impregnated support material is subsequently heated to 400<0>C in hydrogen to activate the catalytic metal on the material. 30. A process according to any of claims 24-28, wherein the impregnated support material is subsequently treated electrochemically in 3 molar sulfuric acid to activate the catalytic metal on the material.