CN1913962A - Synthesis of noble metal sulphide catalysts in a sulphide ion-free aqueous environment - Google Patents

Synthesis of noble metal sulphide catalysts in a sulphide ion-free aqueous environment Download PDF

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CN1913962A
CN1913962A CNA2005800035175A CN200580003517A CN1913962A CN 1913962 A CN1913962 A CN 1913962A CN A2005800035175 A CNA2005800035175 A CN A2005800035175A CN 200580003517 A CN200580003517 A CN 200580003517A CN 1913962 A CN1913962 A CN 1913962A
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noble metal
catalyst
sulphide
solution
metal precursor
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CN100428988C (en
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R·J·艾伦
A·F·古拉
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Industrie de Nora SpA
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De Nora Elettrodi SpA
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    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
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    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
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    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/04—Sulfides
    • B01J27/043—Sulfides with iron group metals or platinum group metals
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    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/04—Sulfides
    • B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
    • B01J27/051—Molybdenum
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/20—Sulfiding
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    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
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    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
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    • H01M4/88—Processes of manufacture
    • H01M4/8803—Supports for the deposition of the catalytic active composition
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    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
    • H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B01J27/04—Sulfides
    • B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
    • B01J27/051—Molybdenum
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Abstract

The invention relates to a catalyst, in particular to a noble metal sulphide electrocatalyst, obtained by reacting the precursor of at least one noble metal with a thionic species in an aqueous environment essentially free of sulphide ions, and to a method for producing the same.

Description

Synthesis of noble metal sulphide catalysts in aqueous environment free of sulphide ions
Technical Field
The invention relates to a catalyst, in particular to a noble metal sulfide electrocatalyst and a preparation method thereof.
Background
Noble metal chalcogenides are widely known in the electrocatalytic field; in particular, electrocatalysts based on sulphides of rhodium and ruthenium are commonly incorporated into gas diffusion electrodes for use as oxidation-reduction cathodes in highly corrosive environments, for example in depolarised electrolysis of hydrochloric acid.
Noble metal sulphides for electrocatalysis are prepared by spraying hydrogen sulphide in an aqueous solution of a corresponding noble metal precursor, typically a chloride, as disclosed for example in US6,149,782 which relates to a rhodium sulphide catalyst. The synthesis of noble metal sulphide catalysts with hydrogen sulphide in aqueous solution is conventionally carried out in the presence of a conductive support, which in most cases consists of carbon particles. In this way, the noble metal sulphide is selectively precipitated on the surface of the carbon particles, and the resulting product is a carbon supported catalyst which is particularly suitable for incorporation into gas diffusion electrode structures characterised by high efficiency at reduced noble metal loading. High surface area carbon blacks, such as Vulcan XC-72, available from Cabot corp./USA, are particularly suitable in this range.
A different process for preparing a carbon-supported noble metal sulphide catalyst comprises: the carbon support is initially moisture impregnated with a noble metal precursor salt, such as a noble metal chloride, followed by evaporation of the solvent and gas phase reaction in a dilute hydrogen sulfide atmosphere at ambient or elevated temperature to form sulfides in a stable phase. For example, it is disclosed in co-pending provisional application 60/473,543, which relates to sulfiding ruthenium catalysts.
In the case where the noble metal is rhodium, the noble metal sulphide catalyst thus obtained should be subjected to an appropriate stabilising heat treatment at a temperature generally in the range 300-700 ℃ before use. In other cases, temperatures as low as 150 ℃ may be sufficient for proper heat treatment.
Although these catalysts show good performance in terms of redox activity and stability in highly corrosive environments, which makes them practically the only usable substance for redox catalysis in hydrochloric acid electrolysis, some inconveniences have affected their production route via hydrogen sulphide.
First, the use of highly dangerous substances in their synthesis, such as hydrogen sulfide, which is a flammable and toxic gas, raises serious environmental and human health concerns. The disposal of hydrogen sulphide is a very delicate matter and one can only dispose of it by means of expensive safety checks.
Secondly, precipitation in the presence of free sulfide ions (sulfoxides) can lead to the formation of compounds in variable stoichiometry and this can hinder the reproducibility of the desired catalysts, especially in the case of reaction with certain noble metals; furthermore, divalent sulfur ions are toxic and environmentally unfriendly substances.
Other common reactants for sulphide precipitation, such as polysulphides, thioacetic acids or thioacetamides, are not as hazardous as hydrogen sulphide, but the reaction path in an aqueous environment is still followed by pre-ionisation or hydrolysis of these compounds to provide the undesirable free sulphide ions.
Due to the presence of free sulfide ions and especially highly flammable and highly toxic hydrogen sulfide species, there is an urgent need for an alternative route for the synthesis of noble metal sulfides for use in redox catalysis for the successful scale-up of noble metal sulfide catalyst production and indeed for the commercialization of potentially large electrochemical processes such as the depolarised electrolysis of hydrochloric acid.
Object of the Invention
It is an object of the present invention to provide a noble metal sulphide catalyst, optionally supported on carbon particles, by precipitation in an aqueous environment free of hydrogen sulphide and substantially free of sulphide ion species.
It is another object of the present invention to provide a process for the preparation of noble metal sulphide catalysts in an aqueous environment avoiding the use of highly flammable and highly toxic substances.
Description of the invention
In one aspect, the present invention relates to a noble metal sulphide catalyst, preferably supported on high surface area carbon black, obtained by reacting the corresponding noble metal precursor, preferably the chloride, with a sulphur-containing species (thionic species) in aqueous solution. By high surface area carbon black is meant a surface area in excess of 50m2Carbon black per gram. By sulfur-containing species is meant any chemical species containing a sulfur functional group, such as thiosulfate, thioacid (thionic acid), and acid derivatives thereof. In a preferred embodiment, the reaction is carried out in an aqueous solution substantially free of divalent sulfur ions. The catalyst of the invention can be a sulfide of any noble metal or even a mixed sulfide of at least one noble metal with one or more common elements (co-elements); in a preferred embodiment, such noble metals are selected from the group consisting of ruthenium, rhodium, platinum, iridium and palladium.
In the most preferred embodiment, the catalyst of the invention is heat treated at a temperature of 150 ℃ to 700 ℃ prior to use.
The catalysts of the invention are particularly suitable for incorporation into gas diffusion electrode structures produced on conductive webs such as carbon cloths or metal meshes, in particular gas diffusion cathodes for oxygen-depolarised electrolysis of hydrochloric acid or other oxygen-consuming cathodes in highly corrosive environments.
In another aspect, the present invention relates to a method of preparing a noble metal sulfide catalyst in the absence of hydrogen sulfide and in an environment substantially free of free sulfide ions, the method comprising: a solution of a noble metal precursor, optionally a chloride, is reacted with an aqueous solution containing a sulfur-containing species, preferably a sodium or ammonium thiosulfate or tetrathionate solution. The noble metal sulphide catalyst of the invention may comprise sulphides of the noble metal alone or mixed sulphides of one noble metal with one other noble or non-noble metal. Thus, the noble metal precursor solution may contain other noble or non-noble metal precursors. Alternatively, the mixed sulfide catalyst may be prepared by reacting a noble metal precursor solution with a sulfur species containing a second noble or non-noble metal.
It is known that, in general, thiosulfate anions can be disproportionated to give a sulfide ion and a sulfate ion as products, with the formation of the sulfide:
however, the inventors have found that under certain conditions the synthesis of sulfide of noble metals (e.g. ruthenium, rhodium, platinum, iridium or palladium) starting from thiosulfates does not release any detectable free sulfide ions on the way.
Without wishing the invention to be bound to any particular theory, it can be assumed that the process proceeds by direct reaction of the metal ion with one of the two sulfur atoms, causing the remainder to decompose.
In the examples described hereinafter, the inventors have more specifically observed that the preferred path is a partially disproportionated path, which is also known as S2O3 -2Metathesis of a substance in which two S atoms are non-equivalent according to the following stoichiometry:
the inventors have found, inter alia, that thiosulfates react with some transition metals to form metal sulfides at a pH between 0.1 and 4.0 when an aqueous solution containing the reactants is brought to boiling or at a temperature in the range of 50 ℃ to 100 ℃.
When thiosulfate is used for the precipitation of sulfide, the order of addition of the reactants is critical in order to provide the desired sulfide catalyst. In fact, if the thiosulfate is first added to an acidic solution free of the metal to be precipitated, the following disproportionation reaction will occur:
2H++S2O3 -2→S0+SO2+H2O
conversely, if the metal ions are present in solution prior to the addition of thiosulfate, the latter will appear to be stabilized to retard the disproportionation reaction and thus cause metathesis of the sulfide. For other types of sulfur species, the order of addition of the reactants is less important. For example, tetrathionate is very stable in acidic solution and does not undergo disproportionation reactions of the type seen above.
No mention is made in the prior art of other thioacid derivatives such as dithionate (S)2O6 -2) Dithionite salt (S)3O6 -2) Tetrathionate (S)4O6 -2) Pentasulfate (S)5O6 -2) Or heptasulfate (S)7O6 -2) Precipitation of the sulphide takes place and its route is not fully understood. However, the inventors could obtain various noble metal chalcogenides from all these species under the same conditions as the precipitation conditions of thiosulfate, and no free sulfide ions were detected at any step of the process. The precipitation of noble metal or mixed metal sulfides using tetrathionate species (e.g., sodium tetrathionate) is particularly preferred because sodium tetrathionate is a popular and inexpensive commercial product. In this case, the reaction with the transition metal also takes place in a pH range of between 0.1 and 4.0 (most preferably 1.0 and 4.0), and in a temperature range of between 50 ℃ and the boiling temperature.
In a preferred embodiment, the reaction is carried out in the presence of high surface area carbon particles or other inert and preferably electrically conductive particles to obtain a supported noble metal sulphide catalyst. In a preferred embodiment, the solution of the sulfur-containing reactant is added in discrete aliquots, for example, 2 to 10 equal aliquots at 15 second to 10 minute intervals. In a preferred embodiment, after the sulfur-containing reactant solution is added to the noble metal precursor solution, the resulting solution is heated to boiling temperature until the reaction is complete (which may last from 5 minutes to two hours, depending on the precursor and reaction conditions selected). It is preferable that the color of the supernatant after the reaction changes so that the completion of the reaction can be easily detected.
In a most preferred embodiment, the method of the present invention further comprises: the obtained product was subjected to a heat treatment at 150-700 ℃ before use.
The following examples are intended to better illustrate the invention without limiting its scope, which is defined solely by the appended claims.
Example 1
Described herein is a process for precipitating rhodium sulphide on carbon from an acidic aqueous solution that does not contain sulphide ions. The precipitation reaction of other noble metal sulphide catalysts, such as sulphides of ruthenium, platinum, palladium or iridium, requires only minor adjustments which are readily available to the skilled person.
7.62g of RhCl3·H2O was dissolved in 1 liter of deionized water, and the solution was refluxed (preparation of noble metal precursor solution).
7g of Vulcan XC72-R high surface area carbon black from Cabot Corporation was added to the solution and the mixture was sonicated at 40 ℃ for 1 hour (preparation of noble metal precursor solution further containing carbon particles).
8.64g (NH)4)2S2O3After dilution in 60ml of deionized water, the pH was measured to be 7.64 (preparation of an aqueous solution containing a sulfur-containing substance).
The rhodium/Vulcan solution was heated to 70 ℃ while stirring and monitoring the pH. Once 70 ℃ was reached, the thiosulfate solution was added in 4 aliquots (15ml each) every two minutes. Between each addition, the stability of the pH, temperature and color of the solution was checked.
After the last aliquot of thiosulfate solution was added, the resulting solution was heated to 100 ℃ and held at temperature for 1 hour. The reaction was monitored by detecting the change in color: an initial dark pink/orange colour which gradually turned brown as the reaction proceeded and finally turned colourless as the reaction was complete, indicating that the product was fully adsorbed on the carbon. Sampling tests were also performed at this stage at various times using lead acetate paper, which confirmed the absence of free sulfide ions at any time in the reaction environment. The precipitate was allowed to settle and then filtered; the filtrate was washed with 1000ml of deionized water to remove any remaining reactants, then the filter cake was collected and air dried at 110 ℃ overnight.
The dried product was finally heat treated at 650 ℃ for 1 hour under flowing argon, resulting in a weight loss of 22.15%.
The performance of the resulting carbon-supported catalyst was first tested in a corrosion test to test its stability in a hydrochloric acid electrolysis environment.
To achieve this, a portion of the sample was heated to boiling in a chlorine saturated HCl solution under the same conditions as disclosed in example 4 of US6,149,782. The color of the resulting solution was a characteristic pinkish color of the more stable form of rhodium sulfide.
The actual performance of the catalyst prepared according to the process of the invention and incorporated into a gas diffusion structure on a conductive mesh known in the art in hydrochloric acid electrolysis was also examined. ELAT carbon cloth based gas diffusers produced by De Nora North America/USA at 1mg/cm2The noble metal loading of (a) yields a catalyst/binder layer; PTFE in aqueous suspension is used as a binder. The gas diffusion electrode thus obtained was sintered at 340 ℃ under forced ventilation and then used as an oxygen-reducing cathode in a hydrochloric acid electrolysis laboratory cell. Recorded at 4kA/m during two weeks of operation2A stable voltage of less than 1.2V was sustained, which is a proof of excellent electrochemical performance.
Example 2
A rhodium sulphide catalyst equivalent to that of the previous example was prepared in the same way, except that: sodium tetrathionate was used as the sulfur-containing species instead of ammonium thiosulfate.
7.62g of RhCl3·H2O was dissolved in 1 liter of deionized water, and the solution was refluxed (preparation of noble metal precursor solution).
7g of Vulcan XC72-R high surface area carbon black from Cabot Corporation was added to the solution and the mixture was sonicated at 40 ℃ for 1 hour (preparation of noble metal precursor solution further containing carbon particles).
17.86g of Na2S4O6·2H2The pH of the O solution was measured to be 7.72 after dilution in 100ml of deionized water (preparation of an aqueous solution containing a sulfur-containing substance).
The rhodium/Vulcan solution was heated to 70 ℃ while stirring and monitoring the pH. Once 70 ℃ was reached, tetrathionate solution was added in 4 aliquots (25ml each) every two minutes. Between each addition, the stability of the pH, temperature and color of the solution was checked.
After the last aliquot of tetrathionate solution was added, the resulting solution was heated to boiling for 1 hour. The reaction was monitored by detecting the change in color: the initial yellow color, which gradually turns brown as the reaction proceeds, eventually turns colorless as the reaction is complete, indicating that the product is fully adsorbed on the carbon. Sampling tests were also performed at this stage at various times using lead acetate paper, which confirmed the absence of free sulfide ions at any time in the reaction environment. The precipitate was allowed to settle and then filtered; the filtrate was washed with 1000ml of deionized water to remove any remaining reactants, then the filter cake was collected and air dried at 110 ℃ overnight.
The dried product was finally heat treated at 650 ℃ for 2 hours under flowing nitrogen, resulting in a weight loss of 24.65%.
The obtained carbon-supported catalyst was subjected to the same corrosion and electrochemical tests as in the previous examples, showing the same results.
The same rhodium sulphide catalyst is obtained by using the sodium tetrathionate, sodium heptathionate and sodium tetrathionate precursors previously prepared according to known procedures in the presence of minor adjustments readily available to the skilled person. Similar corrosion and electrochemical results were obtained in these cases.
Example 3
Rhodium-molybdenum sulfideA catalyst prepared by the following process: to a 500ml beaker was added 250ml of previously refluxed 3g/l RhCl3·H2O solution (ca. 0.75g rhodium, corresponding to 0.0073 moles).
3.37g of Vulcan XC72-R high surface area carbon black from Cabot Corporation was added to the solution and the mixture was sonicated at 40 ℃ for 1 hour (preparation of noble metal precursor solution further containing carbon particles).
1.9g of tetrathiomolybdate (NH)4)MoS4Diluted in 70ml of deionised water (preparation of the second metal containing sulphur species, in this case a non-noble metal thioate).
The rhodium-Vulcan precursor solution was heated to 70 ℃ while stirring and monitoring the pH. Once 70 ℃ was reached, the tetrathiomolybdate solution was added in 4 aliquots, once every two minutes. Between each addition, the stability of the pH, temperature and color of the solution was checked.
After the last aliquot of tetrathiomolybdate solution was added, the resulting solution was heated to boiling for 1 hour. The reaction was monitored by detecting the change in color: the initial yellow color, which gradually changed to pale yellow as the reaction proceeded, eventually became colorless as the reaction was completed, indicating that the product was fully adsorbed on the carbon. Sampling tests were also performed at this stage at various times using lead acetate paper, which confirmed the absence of free sulfide ions at any time in the reaction environment. The precipitate was allowed to settle and then filtered; the filtrate was washed with 500ml of warm (80 ℃) deionised water to remove any remaining reactants, then the filter cake was collected and air dried at 110 ℃ overnight.
Example 4
A ruthenium sulphide-rhodium catalyst prepared by the process of: into a 500ml beaker, 100ml of previously refluxed 12g/l RuCl was added in the resulting weight ratio of about 80% Ru and 20% Rh3·H2O solution (about 1.2g Ru)+3) And 100ml of 3g/l RhCl previously refluxed3·H2O solution (about 0.75g Rh).
To bring the solution to 350ml with deionized water, 3.5g of Vulcan XC72-R high surface area carbon black from Cabot Corporation was added to the solution. The mixture was sonicated at 40 ℃ for 1 hour (preparation of two different noble metal precursor solutions further containing carbon particles).
4.35g (NH)4)2S2O3After dilution in 20ml of deionized water, the pH was determined to be 7.64 (preparation of an aqueous solution containing a sulfur-containing substance).
The rhodium-ruthenium/Vulcan solution was heated to 70 ℃ while stirring and monitoring the pH. Once 70 ℃ was reached, the thiosulfate solution was added in 4 aliquots (5 ml each) every two minutes. Between each addition, the stability of the pH, temperature and color of the solution was checked.
After the last aliquot of thiosulfate solution was added, the resulting solution was heated to 100 ℃ and incubated for 1 hour. The reaction was monitored by detecting the change in color: an initial dark pink/orange colour which gradually turned brown as the reaction proceeded and finally turned colourless as the reaction was complete, indicating that the product was fully adsorbed on the carbon. Sampling tests were also performed at this stage at various times using lead acetate paper, which confirmed the absence of free sulfide ions at any time in the reaction environment. The precipitate was allowed to settle and then filtered; the filtrate was washed with 700ml warm deionized water to remove any remaining reactants, then the filter cake was collected and air dried at 110 ℃ overnight.
The above description should not be taken as limiting the invention, which may be embodied differently without departing from its scope, and its extension is defined only by the appended claims.
In the description and claims of this application, the word "comprise" and variations such as "comprises" and "comprising" are not intended to exclude the presence of other elements or additional components.

Claims (18)

1. A noble metal sulphide catalyst obtained by reacting at least one noble metal precursor with a sulphur-containing species in an aqueous environment substantially free of sulphide ions.
2. A carbon-supported noble metal sulphide catalyst obtained by reacting at least one noble metal precursor with a sulphur-containing species in an aqueous environment containing suspended carbon particles substantially free of sulphide ions.
3. The catalyst of claim 2 wherein said carbon particles are of surface area in excess of 50m2Carbon black particles per gram.
4. A catalyst as claimed in any one of claims 1 to 3 wherein the pH of the aqueous environment is between 0.1 and 4.
5. The catalyst of any of claims 1-4, wherein the at least one noble metal precursor is a noble metal chloride.
6. The catalyst of any one of claims 1-4, wherein the at least one noble metal is selected from the group consisting of ruthenium, rhodium, platinum, iridium, and palladium.
7. The catalyst of any one of claims 1 to 6, wherein the sulfur species is selected from the group consisting of thiosulfate, dithionate, trithionate, tetrathionate, pentathionate, heptathionate, and noble or non-noble metal thioate.
8. The catalyst of claim 7, further heat treated at a temperature between 150 ℃ and 700 ℃.
9. A gas diffusion electrode comprising a catalyst according to any preceding claim on a conductive mesh.
10. A method of preparing a noble metal sulfide catalyst, the method comprising: reacting a solution of at least one noble metal precursor, optionally a chloride, with an aqueous solution containing a sulfur species in a substantially sulfide-free environment.
11. The method of claim 10 wherein the pH of the solution of the at least one precious metal precursor and the aqueous solution containing the sulfur species is between 0.1 and 4.
12. The method of claim 11, wherein the solution of the at least one noble metal precursor further comprises carbon particles, optionally with a surface area of more than 50m2Carbon black per gram.
13. The process of any one of claims 10 to 12, wherein the sulphur-containing species is selected from thiosulphates, dithionates, tetrathionates, pentathionates, heptathionates and noble or non-noble metal thionates, optionally as sodium or ammonium salts.
14. The method of claim 10 wherein the aqueous solution containing the sulfur species is added to the aqueous solution of the noble metal precursor in discrete aliquots, optionally 2 to 10 equal aliquots, at time intervals ranging from 15 seconds to 10 minutes.
15. The process of any one of claims 10 to 14, wherein the aqueous solution containing the sulfur species is added to the at least one noble metal precursor solution and the resulting solution is brought to the boiling temperature for 5 to 120 minutes until the reaction is complete.
16. The method of claim 15, wherein completion of the reaction is determined by detecting a color change.
17. The process as recited in claim 15, further comprising separating the resulting noble metal sulfide catalyst and heat treating it at a temperature between 150 ℃ and 700 ℃.
18. The process of any of claims 10-17, wherein the at least one noble metal is selected from the group consisting of ruthenium, rhodium, platinum, iridium, and palladium.
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CN105013512A (en) * 2015-06-08 2015-11-04 中国科学院长春应用化学研究所 Self-supporting transitional metal sulfide catalyst and preparation methods and applications thereof
CN108823602A (en) * 2018-07-12 2018-11-16 北京化工大学 A kind of vulcanization ruthenium particulate composite, preparation method and the usage

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DE3884451T2 (en) * 1987-04-22 1994-02-03 Sumitomo Metal Mining Co Catalysts for the hydrogenating treatment of hydrocarbons and their activation.
JP3368179B2 (en) * 1997-08-01 2003-01-20 松下電器産業株式会社 Preparation of electrode catalyst powder
US6149782A (en) * 1999-05-27 2000-11-21 De Nora S.P.A Rhodium electrocatalyst and method of preparation
CN1133728C (en) * 2001-01-05 2004-01-07 中国石油化工股份有限公司 Sulfurizing process of catalyst for hydroprocessing of heavy oil

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Publication number Priority date Publication date Assignee Title
CN105013512A (en) * 2015-06-08 2015-11-04 中国科学院长春应用化学研究所 Self-supporting transitional metal sulfide catalyst and preparation methods and applications thereof
CN108823602A (en) * 2018-07-12 2018-11-16 北京化工大学 A kind of vulcanization ruthenium particulate composite, preparation method and the usage

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