Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/17—Metallic particles coated with metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/18—Non-metallic particles coated with metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/42—Coating with noble metals
  • C23C18/44—Coating with noble metals using reducing agents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/48—Coating with alloys
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• platinum and platinum alloys containing up to about 20% rhodium, up to about 10% iridium and up to about 10% ruthenium on an active surface wherein the bath is an alkaline platinum IV hydroxide solution containing about 2 to about grams per liter of platinum, an alkali metal hydroxide to give a minimum bath pH of about 8, up to about 1 mole per liter of a stabilized such as ethylamine, and up to about 1 gram per literof hydrazine.
• Platinum deposits produced in the absence of the stabilizer have catalytic properties whereas platinum and platinum alloy depositsproducedin the presence ofthe stabilizer are bright.
• the present invention relates to the production of composite powders and, more particularly, to the production' of powder and powder compacts having a platinum deposit on the powder particle surface. It also relates to the deposition of protective coatings of platinum and platinum alloys on a number of less noble metals.
• one metal can be coated with a layer of another metal by various processes, including welding, vapor deposition, soldering, chemical deposition, electroplating and the like.
• Composite products produced thereby have utility in numerous applications which are commonly encountered.
• platinum is commonly electrodeposited on various substrates for the purpose of providing'a corrosion resistant layer thereon.
• the choice of methods of deposition isseverely limited. For example, if a process involving even moderate heat is used, the product is like ly to exhibit poor catalytic activity.
• particulate materials such as nickel powder and graphite powder compacts can be provided with an advantageous catalytically active platinum deposit.
• Another object-of the invention is to provide a novel process for the production of catalytically active platinumnickel and platinum-graphite structures.
• the invention also contemplates providing catalytically active composite structures made by a novel process.
• the invention is also directed to a process for the deposition of platinum and of several platinum alloys which are useful as decorative surfaces or as protective coatings for less noble metals.
• the present invention contemplates a non-electrolytic process for depositing platinum and platinum alloys containing a metal from the group consisting of rhodium, iridium and ruthenium on surfaces, including nickel, copper and graphite surfaces, comprising chemically reducing the said platinum metals from a complex alkaline platinum IV hydroxide solution upon an active substrate material by the action of hydrazine.
• the reduction process as contemplated in accordance with the present invention is an autocatalytic reaction, that is, deposited platinum metal or alloy itself catalyzes additional deposition of the platinum metal or alloy.
• aqueous solutions or baths from which platinum can be deposited contain, in solution as the platinum IV hydroxide, about 2 to 20 grams per liter (g.p.l.), e.g., about 2.4 to about 10 g.p.l., of platinum, about 0.1 to about 1 g.p.l.
• a soluble alkali metal hydroxide suflicient to give a minimum pH of about 8, e.g., pH 9 or pH 10 or higher, and up to about 1 'mole per liter (-m.p.l.), e.g., about 0.01 to about 1 rn.p.l., of a bath-soluble and bath-compatible stabilizer characterized by a trivalent nitrogen integer and exemplified by compounds from the group consisting of ethylamine, the sodium salt of ethylene diamine tetraacetic acid (EDTA), quinoline and sulfamate ion (added to the bath, for example, as sulfamic acid).
• EDTA ethylene diamine tetraacetic acid
• Materials such as nickel and alloys thereof, graphite, iron, copper, molybdenum, silver, tantalum, and titanium can be coated with platinum merely by immersing them in the aforedescribed solutions and holding them therein while-maintaining the temperature of .the solution, at about 25. C. to about 35 C.
• Bath compositions contemplated in accordance with the invention are stable and can be stored. Generally, hydrazineis not added to the bath until plating is to bestarted.
• the "bath may readily be prepared by boiling a water solution of chloroplatinic acid with anexcess vof sodium hydroxide.
• the end point of the reaction is marked by a solution color change from the characteristic blood red of chloroplating acid to an orange characteristic of a water solution containing sodium platinum IV hydroxide [Na Pt(OH) Sodium chloride generated by the reaction is not harmful.
• the bath pH is maintained well over on the alkaline side, e.g., pH 8 or higher, to prevent undesired hydrolysis of the solution.
• bath-soluble salts of these metals are introduced into the bath.
• Suitable salts for this purpose include ammonium rhodium III chloride and the corresponding salts of iridium and ruthenium, rhodium III nitrate [Rh(NO diammonium sodium rhodium III chloride [(NH NaRhCl and ammonium rhodium III nitrite [(NH Rh(NO Rhodium can be introduced into the bath in amounts up to about 20%, by weight of the platinum content of the bath while iridium and ruthenium can be introduced into the ba h in amounts up to about 10%, by weight, of the platinum content of the bath.
• Hydrazine may be added to the bath as the hydrate solution or as hydrazine sulfate or hydrazine chloride dissolved in water or in solution with sodium or potassium hydroxide.
• platinum or platinum alloys upon the surface of nickel and carbon (graphite) particles and within the pores of porous nickel and graphite structures:
• Such deposits are of a finely divided nature, have an extended surface, have enhanced catalytic properties, and are useful in the production of fuel cell electrodes and other catalytic bodies.
• These finely divided catalytic deposits are advantageously produced from baths deV id of any stabilizer.
• An advantageous bath composition for providing catalytic deposits is set forth in Table I:
• a bath such as set forth in Table I can be used at a temperature of about 25 C. to about 30 C. When f rmulating such a bath it is necessary to avoid contaminants which may tend to inhibit the catalytic properties of the deposited platinum. Thus, elements such as lead, arsenic, and dimethylglyoximine should be carefully excluded from the bath. It is also contemplated in accordance with invention to employ baths wherein the hydrazine content at any given moment is low, e.g., about 0.1 g.p.l. to about 0.2 g.p.l. Hydrazine preferably can be added either continuously or in portions during a deposition run.
• a stabilizer such as ethylamine is also employed in the bath and a bath composition as set forth in Table II is quite suitable.
• Table II Pt (as sodium platinum IV hydroxide) about 10 g.p.l. NaOH to pH 10. Hydrazine 0.1 to 1 g.p.l. Ethylamine 0.5 to 45 g.p.l. Water Balance.
• Baths such as set forth in Table II can be used at temperatures of about 25 C. to about 35 C. and should be devoid of those aforelisted substances which interfere with deposition of the platinum.
• EXAMPLE I An aqueous bath containing about 5.2 g.p.l. of sodium platinum IV hydroxide (approximately 3 g.p.l. platinum) and about 10 g.p.l. of NaOH was prepared and a quantity of very finely divided carbonyl nickel powder was stirred into the bath. The bath was warmed to 30 C. and about 1 g.p.l. of hydrazine was added. After a time, the bath was found to be devoid of platinum which was deposited in finely divided form on the nickel powder. After washing and drying the metal powder, it was not possible to separate the platinum from the nickel by magnetic or flotation methods.
• Nickel powder was successfully coated with a catalytically active platinum deposit by barrel plating said nickel powder using a barrel made of a clear polymethylmethacrylate plastic material and a bath similar to the bath employed in Example I except that hydrazine was added in small increments during the run.
• Plating time was 150 minutes and the platinum content of the coated powder was about 5% by weight.
• EXAMPLE IV A water solution containing about 5 g.p.l. of platinum as sodium platinum IV hydroxide with sodium hydroxide to give a solution pH of about 8 was prepared. Porous graphite discs about 0.25 inch thick and about 2.5 inches in diameter, having a total porosity of about 0.33 cubic centimeter per gram with approximately 85% of the pores having a pore diameter of about 0.8 to 10 microns and a weight of about 13 grams were soaked in a hydrazine solution having a one molar hydrazine concentration for about 15 minutes. The sodium platinum IV hydroxide solution was passed through the graphite discs in calculated quantity until the platinum content of the solution was exhausted.
• the discs were washed with distilled water until free of alkali, dried with alcohol and acetone and oven dried at 120 C.
• the discs were found to contain about 6% platinum by weight.
• the thus-prepared discs are satisfactory when employed as anodes in a methanol-oxygen fuel cell.
• EXAMPLE V An aqueous bath containing 10 g.p.l. of platinum as sodium platinum IV hydroxide, about 5 g.p.l. of NaOH and about 10 g.p.l. of ethylamine was prepared. Two separate runs were made depositing platinum upon copper from this bath, one at 25 C. and the other at 35 C. Hydrazine was added in small increments to the bath to provide a concentration of about 1 g.p.l. therein. Bright, uniform, metallic appearing deposits of platinum were formed on copper under these conditions. Plating rate was about 300 microinches per hour at 25 C. and about 500 microinches per hour at 35 C.
• Deposits of platinum-rhodium alloys may be produced on metallic surfaces according to the compositions set forth in Table III.
• Baths as set forth in Table III may be operated in the temperature range of from 25 C. to 35 C.
• EXAMPLE VI active metal surfaces It is also particularly advantageous in the production of platinum plates on surfaces such as printed circuits elements which cannot conveniently be coated by electrodeposition.
• Alloys containing ratios up to 80 platinum to 20 rhodium using baths containing rhodium in amounts up to about 20% of the platinum content on a weight basis can be produced.
• Other alloys of platinum such as platinumiridium alloys containing up to about iridium, e.g., up'to about 5% iridium, and platinum-ruthenium alloys containing up to about 10% ruthenium, e.g., up to about 5% ruthenium, can be produced.
• a stabilizer e.g., ethylamine
• alloys are produced to substantially constant compositions in about the weight ratio of metals present in the bath.
• Palladium cannot be plated from baths containing a strong alkali such as sodium hydroxide or potassium hydroxide because palladium precipitates from the baths. Accordingly, palladium may not be present in the bath in any appreciable amount and, most advantageously, is absent. While either sodium hydroxide or potassium hydroxide may be employed in preparing the bath, sodium carbonate and potassium carbonate may not be employed for the purpose because the carbonates cause slud-ging of the bath. Furthermore, ammonium hydroxide may not be employed in amounts exceeding about 1 g.p.l. calculated as ammonia (NH because greater amounts of ammonia cause precipitation of platinum from solution and also creates difficulties in plating upon a copper substrate.
• a strong alkali such as sodium hydroxide or potassium hydroxide
• the special bath provided in accordance with the invention may be considered, particularly with reference to platinum, as a solution in aqueous sodium (or potassium) hydroxide of a platinum salt.
• Sodium and/or potassium hydroxide may be present in the bath in amounts up to saturation.
• the stabilizer e.g., ethylamine
• ethylamine is characterized by a trivalent nitrogen integer and is bath-soluble and bath-compatible.
• immiscible, oily, tarry and otherwise physically undesirable compounds are not to be employed in the bath as otherwise the results achieved in accordance with the invention are not achieved.
• platinum and platinum alloy deposits can be produced upon any clean active metal, alloy or carbon surface.
• Surfaces of materials such as glass, plastics and ceramics which are not active can be rendered active by depositing an active preliminary coat of a material such as platinum, palladium, etc.
• Surfaces made of copper, nickel, nickel alloys, iron, titanium, tantalum, carbon, molybdenum, etc., can be plated with platinum and platinum alloy deposits in accordance with the invention.
• a bath for depositing platinum consisting essentially of water, about 2 to about grams per liter of platinum as a platinum IX hydroxide, an alkali from the group consisting of sodium hydroxide and potassium hydroxide to provide a minimum bath pH of about 8, up to about 1 gram per liter of hydrazone, and up to about 1 mole per liter of a bath-soluble and bath-compatible stabilizer containing a trivalent nitrogen integer.
• a bath for depositing platinum consisting essentially of water, about 2.4 to about 10 grams per liter of platinum as a platinum IV hydroxide, an alkali from the group consisting of sodium hydroxideand potassium hydroxide to provide a minimum bath pH of about 10, up to about 1 gram per liter of hydrazine, and up to about 1 mole per liter of a bath-soluble and bath-compatible stabilizer containing a trivalent nitrogen integer.
• a bath according to claim 4 wherein the stabilizer is selected from the group consisting of ethylamine, the sodium salt of EDTA, quinoline and sulfamate ion.
• a bath for depositing platinum consisting essentially of water, about 5.2 to about 7.2 grams per liter of platinum as sodium platinum IV hydroxide, an amount of sodium hydroxide to provide a bath pH of about 12.5, up to about 1 mole per liter of a bath-soluble and bathcompatible stabilizer containing a trivalent nitrogen integer, and hydrazine in an amount up to about 1 gram per liter.
• a process for depositing platinum in a form comprising an extended surface and having enhanced catalytic properties which comprises immersing an active surface into a bath containing about 2 to about 20 grams per liter of platinum as a platinum IV hydroxide, an alkali from group consisting of sodium hydroxide and potassium hydroxide to provide a bath pH of at least about 8, and the balance essentially water, and introducing into said bath hydrazine in an amount up to about 1 gram per liter to deposit platinum upon said. active surface.
• a process for depositing platinum which comprises immersing an active surface into a bath containing about 2 to about 20 grams per liter of platinum as a platinum IV hydroxide, an alkali from the group consisting of sodium hydroxide and potassium hydroxide to provide a bath pH of at least about 8, up to about 1 mole per liter of a bath-soluble and bath-compatible stabilizer containing a trivalent nitrogen integer, and the balance essentially water, and introducing into said bathhydrazine in an amount up to about 1 gram per liter to deposit platinum upon said active surface.
• a process according to claim 8 wherein the active surface is made of a material from the group consisting of copper, nickel, nickel alloys, iron, titanium, tantalum, carbon, and molybdenum.
• the process for depositing platinum and platinum alloys with rhodium, iridium and ruthenium which comprises establishing a bath containing about 2 to about 20 grams per liter of platinum as a platinum IV hydroxide, a metal from the group consisting of rhodium, iridium and ruthenium as a bath-soluble salt in an amount such that rhodium is up to about 20% by weight of platinum present and iridium and ruthenium are in amounts up to about 10% each by weight of platinum present, an alkali from the group consisting of potassium hydroxide and sodium hydroxide to provide a minimum bath pH of about 8, about 0.01 to about 1 mole per liter of a bathsoluble and bath-compatible stabilizer containing a trivalent nitrogen integer, and the balance essentially water, introducing into said bath hydrazine in an amount up to about 1 gram per liter, and introducing an active surface into said bath to deposit a metal from the group consisting of platinum and platinum alloys with rhodium, i
• a process according to claim 10 wherein the platinum content in the bath is about 10 to about 20 grams per liter.
• a process for depositing platinum which comprises establishing a bath containing about 2.4 to about 10 grams per liter of platinum as sodium platinum IV hydroxide to provide a bath pH of about 10, up to about 1 mole per liter of a bath soluble and bath-compatible stabilizer containing a trivalent nitrogen integer, introducing into said bath hydrazine in an amount up to about 1 gram per liter, introducing into said bath an active surface, and depositing platinum upon said surface.
• a process for depositing platinum which comprises establishing a bath containing about 5.2 to about 7.2 grams per liter of platinum as sodium platinum IV hydroxide, an amount of sodium hydroxide to provide a bath pH of about 12.5, up to about 1 mole per liter of a bath-soluble and bath-compatible stabilizer containing References Cited UNITED STATES PATENTS 2,872,359 2/1959 Saubestre 117l30 X 3,105,772 10/1963 Loiseleur 117--54 X 3,147,154 9/1964 Cole et a1 117130 X ALFRED L. LEAVITT, Primary Examiner T. E. BOKAN, Assistant Examiner US. Cl. X.R.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Electrochemistry (AREA)
• Catalysts (AREA)
• Chemically Coating (AREA)
• Inert Electrodes (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Cited By (18)

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Citations (3)

• 1965
  • 1965-10-21 US US500212A patent/US3486928A/en not_active Expired - Lifetime
• 1966
  • 1966-10-11 GB GB45445/66A patent/GB1097010A/en not_active Expired
  • 1966-10-20 DE DE19661521339 patent/DE1521339A1/de active Pending
  • 1966-10-20 NL NL6614828A patent/NL6614828A/xx unknown
  • 1966-10-21 BE BE688701D patent/BE688701A/xx unknown
  • 1966-10-21 CH CH1527266A patent/CH466665A/fr unknown
  • 1966-10-21 SE SE14403/66A patent/SE327877B/xx unknown

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