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A METHOD OF ELECTROLESS DEPOSITION OF PLATINUM GROUP METALS AND THEIR ALLOYS AND A PLATING BATH USED THEREIN

20200095686 ยท 2020-03-26

    Inventors

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    Abstract

    The invention relates to a method of electroless deposition of platinum group metals and their alloys from a plating bath onto a substrate, comprising a reduction step of one or more platinum group metal precursors with a reducing agent, wherein the reducing agent is a primary or secondary monohydroxyalcohol or a mixture of primary or secondary monohydroxyalcohols. The invention also provides a plating bath suitable for use in said method.

    Claims

    1. A method of electroless deposition of platinum group metals and their alloys from a plating bath onto a substrate, comprising a reduction step of one or more platinum group metal precursors with a reducing agent, wherein the reducing agent is a primary or secondary monohydroxyalcohol or a mixture of primary or secondary monohydroxyalcohols.

    2. The method of claim 1, wherein the monohydroxyalcohol has a general formula ##STR00002## wherein R.sub.1 and R.sub.2 are the same or different and each of them is independently selected from a group comprising hydrogen atom, a straight or branched C.sub.1-7-alkyl group, C.sub.3-8-aryl group, C.sub.4-8-aralkyl group and C.sub.4-8-alkaryl group.

    3. The method of claim 1, wherein R.sub.1 and R.sub.2 are independently selected from a group comprising H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, CH(CH.sub.3).sub.2, C.sub.4H.sub.9, CH.sub.2CH(CH.sub.3).sub.2, CH(CH.sub.3)C.sub.2H.sub.5, C(CH.sub.3).sub.3, C.sub.5H.sub.11, CH(CH.sub.3)C.sub.3H.sub.7, CH.sub.2CH(CH.sub.3)C.sub.2H.sub.5, C.sub.2H.sub.4CH(CH.sub.3).sub.2, C(CH.sub.3).sub.2C.sub.2H.sub.5, CH(CH.sub.3)CH(CH.sub.3).sub.2, CH.sub.2C(CH.sub.3).sub.3, CH(C.sub.2H.sub.5).sub.2, C.sub.6H.sub.13, C.sub.7H.sub.15, and CH(C.sub.2H.sub.5)(C.sub.4H.sub.9).

    4. The method of claims 1, wherein the monohydroxyalcohol is selected from a group comprising methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 2,2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3-dimethylbutan-2-ol, 2-ethylbutan-1-ol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol and 2-ethylhexan-1-ol.

    5. The method of claim 1, wherein the monohydroxyalcohol is selected from the group comprising methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 1-heptanol and 1-octanol.

    6. The method of claim 1, wherein the concentration of the monohydroxyalcohol in the plating bath is in the range from 0.02 to 12 M.

    7. The method of claim 6, wherein concentration of the monohydroxyalcohol in the plating bath is in the range from 0.1 to 5 M.

    8. The method of claim 1, wherein the platinum group metal precursor is selected from a group comprising H.sub.2PtCl.sub.6, H.sub.6Cl.sub.2N.sub.2Pt, PtCl.sub.2, PtBr.sub.2, K.sub.2[PtCl.sub.4], Na.sub.2[PtCl.sub.4], Li.sub.2[PtCl.sub.4], H.sub.2Pt(OH).sub.6, Pt(NO.sub.3).sub.2, [Pt(NH.sub.3).sub.4]Cl.sub.2, [Pt(NH.sub.3).sub.4](HCO.sub.3).sub.2, [Pt(NH.sub.3).sub.4](OAc).sub.2, (NH.sub.3).sub.4Pt(NO.sub.3).sub.2, (NH.sub.4).sub.2PtBr.sub.6, K.sub.2PtCl.sub.6, PtSO.sub.4, Pt(HSO.sub.4).sub.2, Pt(ClO.sub.4).sub.2, K.sub.2PtI.sub.6, K.sub.2[Pt(CN).sub.4], cis-[Pt(NH.sub.3).sub.2Cl.sub.2], H.sub.2PdCl.sub.6, H.sub.6Cl.sub.2N.sub.2Pd, PdCl.sub.2, PdBr.sub.2, K.sub.2[PdCl.sub.4], Na.sub.2[PdCl.sub.4], Li.sub.2[PdCl.sub.4], H.sub.2Pd(OH).sub.6, Pd(NO.sub.3).sub.2, [Pd(NH.sub.3).sub.4]Cl.sub.2, [Pd(NH.sub.3).sub.4](HCO.sub.3).sub.2, [Pd(NH.sub.3).sub.4](OAc).sub.2, (NH.sub.4).sub.2PdBr.sub.6, (NH.sub.3).sub.2PdCl.sub.6, PdSO.sub.4, Pd(HSO.sub.4).sub.2, Pd(ClO.sub.4).sub.2, Pd(OAc).sub.2, RuCl.sub.2 ((CH3).sub.2SO).sub.4, RuCl.sub.3, [Ru(NH.sub.3).sub.5(N.sub.2)]Cl.sub.2, Ru(NO.sub.3).sub.3, RuBr.sub.3, RuF.sub.3, Ru(ClO.sub.4).sub.3, K.sub.2RuCl.sub.6, OsI, OsI.sub.2, OsBr.sub.3, OsCl.sub.4, OsF.sub.5, OsF.sub.6, OsOF.sub.5, OsF.sub.7, IrF.sub.6, IrCl.sub.3, IrF.sub.4, IrF.sub.5, Ir(ClO.sub.4).sub.3, K.sub.3[IrCl.sub.6], K.sub.2[IrCl.sub.6], Na.sub.3[IrCl.sub.6], Na.sub.2[IrCl.sub.6], Li.sub.3[IrCl.sub.6], Li.sub.2[IrCl.sub.6], [Ir(NH.sub.3).sub.4Cl.sub.2]Cl, RhF.sub.3, RhF.sub.4, RhCl.sub.3, [Rh(NH.sub.3).sub.5Cl]Cl.sub.2, RhCl[P(C.sub.6H.sub.5).sub.3].sub.3, K[Rh(CO).sub.2Cl.sub.2], Na[Rh(CO).sub.2Cl.sub.2]Li[Rh(CO).sub.2Cl.sub.2], Rh.sub.2(SO.sub.4).sub.3, Rh(HSO.sub.4).sub.3, Rh(ClO.sub.4).sub.3, their hydrates and mixtures of these salts and/or hydrates.

    9. The method of claim 1, wherein the reduction step of one or more platinum group metal precursors is carried out in the presence of a precursor or precursors of different metals, thus forming of alloy comprising one or more platinum group metal and a different metal.

    10. The method of claim 9, wherein the formed alloy comprises two or more metals selected from a group comprising: platinum, palladium, rhodium, iridium, ruthenium, osmium, gold, nickel and copper

    11. The method of claim 1, wherein the precursor concentration in the plating bath is in the range from 1 mM to 1 M, preferably 5 mM to 100 mM, and more preferably from 10 mM to 50 mM.

    12. The method of claim 1, wherein the reduction step is carried out in the temperature between the freezing point and the boiling point of the plating bath.

    13. The method of claim 12, wherein the reduction step is carried out in the temperature from 10 to 80 C., preferably from 0 to 40 C., and more preferably from 10 to 25 C.

    14. The method of claim 1, wherein the plating bath further comprises pH buffer.

    15. The method of claim 1, wherein the pH of the plating bath is below 7.

    16. The method of claim 15, wherein the pH of the plating bath is between 3 and 5.

    17. The method of claim 16, wherein the pH of the plating bath is about 4.

    18. The method of claim 1, wherein the substrate is selected from a group comprising metals, metal alloys, polymeric materials, carbon and silicon.

    19. The method of claim 18, wherein the substrate is selected from the group comprising platinum, palladium, nickel, gold, steel, iron-chromium-aluminum alloys, Nafion, polyethylene, polypropylene, polyethylene terephthalate, graphite and silicon.

    20. The method of claim 1, wherein prior to the reduction step of platinum group metal precursors the surface of the substrate is seeded.

    21. The method of claim 1, wherein after the plating process is completed, the plated substrate undergoes a high temperature treatment.

    22. The method of claim 1, wherein the plating bath further comprises brighteners.

    23. The method of claim 1, wherein the plating bath further comprises an additional reducing agent, preferably a reducing agent selected from a group comprising hydrazine and its derivatives, borohydride or hydrogen hypophosphite

    24. The method of claim 1, wherein the plating bath further comprises 2-methylpropan-2-ol.

    25. A plating bath for electroless deposition of platinum group metals and their alloys, wherein said bath is an aqueous solution comprising a primary or secondary monohydroxyalcohol, or a mixture of primary or secondary monohydroxyalcohols, as the reducing agent and one or more platinum group precursors.

    26. The bath of claim 25, wherein the monohydroxyalcohol has a general formula ##STR00003## wherein R.sub.1 and R.sub.2 are the same or different and each of them independently is selected from a group comprising hydrogen atom, a straight or branched C.sub.1-7-alkyl group, C.sub.3-8-aryl group, C.sub.4-8-aralkyl group and C.sub.4-8-alkaryl group.

    27. The bath of claim 26, wherein R.sub.1 and R.sub.2 are independently selected from a group comprising H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, CH(CH.sub.3).sub.2, C.sub.4H.sub.9, CH.sub.2CH(CH.sub.3).sub.2, CH(CH.sub.3)C.sub.2H.sub.5, C(CH.sub.3).sub.3, C.sub.5H.sub.11, CH(CH.sub.3)C.sub.3H.sub.7, CH.sub.2CH(CH.sub.3)C.sub.2H.sub.5, C.sub.2H.sub.4CH(CH.sub.3).sub.2, C(CH.sub.3).sub.2C.sub.2H.sub.5, CH(CH.sub.3)CH(CH.sub.3).sub.2, CH.sub.2C(CH.sub.3).sub.3, CH(C.sub.2H.sub.5).sub.2, C.sub.6H.sub.13, C.sub.7H.sub.15, and CH(C.sub.2H.sub.5)(C.sub.4H.sub.9).

    28. The bath of claim 27, wherein the monohydroxyalcohol is selected from the group comprising methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 2,2-dimethylbutan-1-ol, 2,3-dimethylbutan-1-ol, 3,3-dimethylbutan-1-ol, 3,3- dimethylbutan-2-ol, 2-ethylbutan-1-ol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol and 2-ethylhexan-1-ol.

    29. The bath of claim 28, wherein the monohydroxyalcohol is selected from the group comprising methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, 1-pentanol, 3-methylbutan-1-ol, 2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, 3-pentanol, 2-pentanol, 3-methyl-2-butanol, 1-hexanol, 1-heptanol and 1-octanol.

    30. The bath of claim 25, wherein the concentration of the monohydroxyalcohol is in the range from 0.02 to 12 M, preferably in the range from 0.1 to 5 M.

    31. The bath of claim 25, wherein it further comprises an additional reducing agent, preferably a reducing agent selected from a group comprising hydrazine and its derivatives, borohydride or hydrogen hypophosphite

    32. The bath of claim 25, wherein the platinum group metal precursor is selected from a group comprising H.sub.2PtCl.sub.6, H.sub.6Cl.sub.2N.sub.2Pt, PtCl.sub.2, PtBr.sub.2, K.sub.2[PtCl.sub.4], Na.sub.2[PtCl.sub.4], Li.sub.2[PtCl.sub.4], H.sub.2Pt(OH).sub.6, Pt(NO.sub.3).sub.2, [Pt(NH.sub.3).sub.4]Cl.sub.2, [Pt(NH.sub.3).sub.4](HCO.sub.3).sub.2, [Pt(NH.sub.3).sub.4](OAc).sub.2, (NH.sub.3).sub.4Pt(NO.sub.3).sub.2, (NH.sub.4).sub.2PtBr.sub.6, K.sub.2PtCl.sub.6, PtSO.sub.4, Pt(HSO.sub.4).sub.2, Pt(ClO.sub.4).sub.2, K.sub.2PtI.sub.6, K.sub.2[Pt(CN).sub.4], cis-[Pt(NH.sub.3).sub.2Cl.sub.2], H.sub.2PdCl.sub.6, H.sub.6Cl.sub.2N.sub.2Pd, PdCl.sub.2, PdBr.sub.2, K.sub.2[PdCl.sub.4], Na.sub.2[PdCl.sub.4], Li.sub.2[PdCl.sub.4], H.sub.2Pd(OH).sub.6, Pd(NO.sub.3).sub.2, [Pd(NH.sub.3).sub.4]Cl.sub.2, [Pd(NH.sub.3).sub.4](HCO.sub.3).sub.2, [Pd(NH.sub.3).sub.4](OAc).sub.2, (NH.sub.4).sub.2PdBr.sub.6, (NH.sub.3).sub.2PdCl.sub.6, PdSO.sub.4, Pd(HSO.sub.4).sub.2, Pd(ClO.sub.4).sub.2, Pd(OAc).sub.2, RuCl.sub.2((CH3).sub.2SO).sub.4, RuCl.sub.3, [Ru(NH.sub.3).sub.5(N.sub.2)]Cl.sub.2, Ru(NO.sub.3).sub.3, RuBr.sub.3, RuF.sub.3, Ru(ClO.sub.4).sub.3, K.sub.2RuCl.sub.6, OsI, OsI.sub.2, OsBr.sub.3, OsCl.sub.4, OsF.sub.5, OsF.sub.6, OsOF.sub.5, OsF.sub.7, IrF.sub.6, IrCl.sub.3, IrF.sub.4, IrF.sub.5, Ir(ClO.sub.4).sub.3, K.sub.3[IrCl.sub.6], K.sub.2[IrCl.sub.6], Na.sub.3[IrCl.sub.6], Na.sub.2[IrCl.sub.6], Li.sub.3[IrCl.sub.6], Li.sub.2[IrCl.sub.6], [Ir(NH.sub.3).sub.4Cl.sub.2]Cl, RhF.sub.3, RhF.sub.4, RhCl.sub.3, [Rh(NH.sub.3).sub.5Cl]Cl.sub.2, RhCl[P(C.sub.6H.sub.5).sub.3].sub.3, K[Rh(CO).sub.2Cl.sub.2], Na[Rh(CO).sub.2Cl.sub.2]Li[Rh(CO).sub.2Cl.sub.2], Rh.sub.2(SO.sub.4).sub.3, Rh(HSO.sub.4).sub.3 and Rh(ClO.sub.4).sub.3, their hydrates or mixtures of these salts and/or hydrates.

    33. The bath of claim 25 wherein the precursor concentration is in the range from 1 mM to 1 M.

    34. The bath of claim 33, wherein the precursor concentration is in the range from 5 mM to 100 mM.

    35. The bath of claim 34, wherein the precursor concentration is in the range from 10 mM to 50 mM.

    36. The bath of claim 25, wherein the pH of the plating bath is below 7.

    37. The bath of claim 36, wherein the pH is between 3 and 5.

    38. The bath of claim 37, wherein the pH of the plating bath is about 4.

    39. The bath of claim 25, wherein it further comprises pH buffer.

    40. The bath of claim 25, wherein it further comprises brighteners.

    41. The bath of claim 25, wherein it further comprises 2-methylpropan-2-ol.

    43. A method for electroless deposition of platinum group metals, comprising electroless depositing of platinum group metals and their alloys, the improvement wherein the electroless deposition of platinum group metals and their alloys is from the plating bath as defined in claim 25.

    Description

    BRIEF DESCRIPTION OF DRAWINGS

    [0048] The subject of the invention is illustrated in a drawing, in which:

    [0049] FIG. 1 presents a photograph of Pt-plated platinum foil, obtained as described in Example 1.

    [0050] FIGS. 2A-2D present a photograph of Pt plated Kanthal (a), Nafion (b), PP (c) and PET (d), obtained as described in Example 2.

    [0051] FIGS. 3A-3B present (a) a photograph of platinum-coated gold plate obtained as described in Example 3 and (b) a SEM micrograph of platinum layer thus obtained.

    [0052] FIGS. 4A-4B present (a) a photograph of a platinum coated graphite disc and (b) a photograph of a platinum coated steel plate obtained as described in Example 4.

    [0053] FIG. 5 presents a photograph of platinum deposited on palladium-coated copper rod obtained as described in Example 5.

    [0054] FIG. 6 presents XP spectrum in Pt 4f/Ir 4f region for alloy deposit prepared as described in Example 7.

    [0055] FIGS. 7A-7O present SEM micrographs of alloy layers obtained on gold substrate as described in Example 8: (a) alloy RhPt (MeOH); (b) Ru (MeOH) (magnification 2.50K); (c) Ru (MeOH) (magnification 100.00K); (d) alloy PtIr (MeOH) (magnification 50.00 K) (e) alloy PtIr (MeOH) (magnification 1.00 K); (f) alloy RhPt (EtOH); (g) alloy RuPt (EtOH); (h) alloy IrPt (EtOH); (i) alloy RhPt (isopropanol) (magnification 1K); (j) alloy IrPt (isopropanol) (magnification 1.00 K); (k) Ru (isopropanol) (magnification 5.00 K); (1) Ru (isopropanol) (magnification 50.00 K); (m) alloy PdPt (isopropanol); (n) alloy IrPt (isopropanol) (magnification 1.00 K); (o) IrPt (isopropanol) (magnification 50.00 K).

    [0056] FIGS. 8A-8C present micrographs of alloy layers obtained on gold substrate in Example 9: (a) alloy RuPt 1:2 (EtOH) (magnification 2.50 K); (b) alloy RuPt 1:6 (EtOH) (magnification 25.00 K); (c) alloy PtIr (BuOH) (magnification 1.00 K); (d) alloy PtIr (BuOH) (magnification 50.00 K).

    [0057] FIG. 9 presents a photograph of platinum deposits on PET and PP substrates obtained as described in Example 10.

    [0058] FIGS. 10A-10D presents data for platinum deposits obtained using different reducing agents, as described in Example 11: (a) Cyclic voltammogram recorded for platinum layers plated on Pt by electroless deposition according to the invention using different reducing agents. Cyclic voltammograms were recorded in 0.5 M sulfuric acid at scan rate v=1 mVs.sup.1; (b) Scanning electron micrograph of a platinum layer deposited on platinum from a methanol containing bath; (c) Scanning electron micrograph of a platinum layer deposited on platinum from a 2-propoanol containing bath; (d) Scanning electron micrograph of a platinum layer deposited on platinum from a 2-butanol containing bath.

    [0059] FIG. 11 presents voltammograms recorded in 0.5 mol dm.sup.3 H.sub.2SO.sub.4 and 0.5 mol dm.sup.3 ethanol at PtIr alloy deposits obtained using different reducing agents as described in Example 13.

    EXAMPLES

    Example 1. Platinum Deposition on Platinum Foil

    [0060] Platinum foil 0.70.70.01 cm in diameter was hydrogen flame annealed and quenched in deionized water. The substrate was subsequently immersed in a solution containing 2.2 M 2-propanol; 0.01 M [PtCl.sub.4].sup.2+Britton-Robins buffer prepared from aqueous solution containing 0.04 M H.sub.3BO.sub.3, 0.04 M H.sub.3PO.sub.4 and 0.04 M CH.sub.3COOH adjusted to pH=4.06 with sodium hydroxide. The plating bath was kept at room temperature for 10 hours. Metallic silver shine coating of 2 m in thickness was thus obtained with the 98% yield. The thickness of the deposited layer and deposition yield was determined based on a weight change of the substrate. FIG. 1 presents a photograph of the Pt-plated platinum foil.

    Example 2. Platinum Deposition on Kanthal, PET, PP, Nafion and Silicon Substrates

    [0061] A Kanthal plate was immersed in a solution containing 2.2 M 2-propanol, 0.01 M [PtCl.sub.4].sup.2+Britton-Robins buffer prepared from aqueous solution containing 0.04 M H.sub.3BO.sub.3, 0.04 M H.sub.3PO.sub.4 and 0.04 M CH.sub.3COOH adjusted to pH=4.06 with sodium hydroxide. The plating bath was kept at room temperature for 12 hours. Metallic silver shine coating was obtained on Kanthal surface. FIG. 2(a) presents a photograph of a platinum plated Kanthal plate.

    [0062] The above method was also used for platinum deposition on polypropylene (PP), polyethylene terephthalate (PET), Nafion and silicon. Metallic silver shine coating was obtained on silicon, PP i PET substrate, whereas grey-black coating on Nafion. Photographs of platinum coated Nafion, PP and PET are presented on FIG. 2 b-d, respectively.

    [0063] In a corresponding manner platinum a metallic silver shine layer was obtained on PP substrate using 2.5 M 1-propanol from the solution having pH 4 and containing 7.5 mM of [PtCl.sub.4].sup.2.

    Example 3. Platinum Deposition on a Gold Substrate

    [0064] A gold plate 0.70.70.05 cm in diameter was seeded using a zincating method (in an aqueous solution containing 1 M of Na.sub.2[Zn(OH).sub.4] in the presence of metallic zinc, the mass of deposited Zn was equal to 50 g). The substrate was subsequently immersed in a solution containing 2.2 M 2-propanol; 0.01 M [PtCl.sub.4].sup.2+Britton-Robins buffer prepared from aqueous solution containing 0.04 M H.sub.3BO.sub.3, 0.04 M H.sub.3PO.sub.4 and 0.04 M CH.sub.3COOH adjusted to pH=4.06 with sodium hydroxide. The plating bath was kept at room temperature for 12 hours. Metallic silver shine coating of 2.4 m in thickness was thus obtained with the 95% yield. FIG. 3a presents a photograph of platinum-coated gold plate. A SEM micrograph of the deposit is shown in FIG. 3b.

    Example 4. Platinum Deposition on Nickel, Steel and Graphite Substrates

    [0065] Platinum deposits on nickel, steel and graphite substrates were obtained as described in Example 3. Metallic silver shine platinum coating was obtained on all substrates. FIG. 4 presents a photograph of a platinum-coated graphite disc (a) and a photograph of a platinum-coated steel plate (b).

    Example 5. Platinum Deposition on Silver, Palladium, PET, PP and Nafion Substrates

    [0066] Platinum deposits on silver, palladium, PET, PP and Nafion substrates were obtained as described in Example 3, with that difference that instead of Na.sub.2[Zn(OH).sub.4], tin (II) chloride (SnCl.sub.2) was used for seeding of the substrate surface. Metallic silver shine platinum coating was obtained on all substrates. FIG. 5 presents a photograph of a platinum deposit on a palladium-coated copper rod with 200 nm of palladium.

    Example 6. Preparation of Rough Platinum Layers for Catalytic Applications

    [0067] Platinum foil 0.70.70.01 cm in diameter was hydrogen flame annealed and quenched in deionized water. The substrate was subsequently immersed in a solution containing 2.85 M of ethanol; 0.01 M [PtCl.sub.4].sup.2+Britton-Robins buffer prepared from aqueous solution containing 0.04 M H.sub.3BO.sub.3, 0.04 M H.sub.3PO.sub.4 and 0.04 M CH.sub.3COOH adjusted to pH=4.06 with sodium hydroxide. The plating bath was kept at room temperature for 1 hour. An adherent grey-black coating of 0.4 m in thickness was thus obtained with the specific roughness factor, R.sub.f=A.sub.specific/A.sub.geometric=130, where A.sub.specific and A.sub.geometric is the specific and geometric surface area of the deposit, respectively. Taking into account the mass of the deposit m=1.63 mg, this correspond to 16.3 m.sup.2/g of mass specific surface area.

    [0068] This type of platinum deposit is particularly suitable for use in catalytic applications.

    Example 7. Preparation of Platinum-Iridium Alloy on a Gold Substrate

    [0069] Gold disc 0.20.05 cm in diameter was seeded using a zincating method (in an aqueous solution containing 1 M of Na.sub.2[Zn(OH).sub.4] in the presence of metallic zinc, the mass of deposited Zn was equal to 20 g). The substrate was subsequently immersed in a solution containing 4 M methanol; 0.01 M [PtCl.sub.4].sup.2+0.01 M [IrCl.sub.4].sup.2+Britton-Robins buffer prepared from aqueous solution containing 0.04 M H.sub.3BO.sub.3, 0.04 M H.sub.3PO.sub.4 and 0.04 M CH.sub.3COOH adjusted to pH=4.06 with sodium hydroxide. The plating bath was kept at room temperature for 24 hours. Metallic silver shine coating of 1 m in thickness was obtained with the 95% yield.

    [0070] The chemical composition and chemical characteristics of the deposit was investigated by X-ray photoelectron spectroscopy. This method was used to confirm the metallic characteristics of the iridium. XP spectrum in Pt 4f/Ir 4f region reveals two doublets. The doublet with components at 60.71 eV and 63.69 eV can be attributed to metallic Ir (Ir 4f.sub.7/2 and Ir 4f.sub.5/2 signals, respectively), whereas signals at 71.34 eV and 74.67 eV can be attributed to metallic Pt (Pt 4f.sub.7/2 and Pt 4f.sub.5/2 signals, respectively). Literature positions for metallic Ir and Pt: 60.81 eV and 63.76 eV for Ir 4f.sub.7/2 and Ir 4f.sub.5/2 signals, respectively and 71.09 eV and 74.42 eV for Pt 4f.sub.7/2 and Pt 4f.sub.5/2 signals, respectively (NIST X-ray Photoelectron Spectroscopy Database, Version 4.1 [National Institute of Standards and Technology, Gaithersburg, 2012); http://srdata.nist.gov/xps/.]) were marked with vertical lines. Small difference between the measured and literature peak positions are most probably caused by alloy formation [Adam Lewera et al.: Core-level Binding Energy Shifts in PtRu nanoparticles: A puzzle resolved. Chem. Phys. Lett. 2007, 44: 39-43). Small doublet at ca. 76.69 eV and 80.02 eV is probably associated with presence of small amount of unreduced Pt, most probably in the form of Pt(IV) compounds. Pt to Ir ratio, determined from XPS data, is equal to 75:25 atomic percent (Pt:Ir). FIG. 6 presents XP spectrum in Pt 4f/Ir 4f region. Two signal doublets, one for Pt and second for Ir can be clearly seen. Reference position of Pt and Ir signals for completely reduced metals are marked with vertical lines.

    Example 8. Preparation of Platinum-Rhodium, -Ruthenium, -Palladium and -Iridium Alloys on a Gold Substrate

    [0071] A possibility of alloy formation was investigated further for different alcohols used as reducing agents and for that purpose the following alloy layers on gold substrate were prepared: platinum-rhodium, platinum-ruthenium, platinum-palladium and platinum-iridium. The process of plating was carried out in a corresponding manner as described in Example 7, however 3 mM K.sub.2PtCl.sub.6 was used as platinum precursor, in consecutive examples 5 M MeOH, 3.5 M EtOH and 2.6 M isopropanol were used as reducing agents, and 6 mM Rh.sup.2+, 6 mM Ru.sup.2+, 7 mM Pd.sup.2+, and 6 mM Ir(IV) were used as precursors of the second PGM in an alloy. The table below summarizes the conditions used for alloy plating of the substrate, as well as the properties of the obtained layer. The alloy formation and composition thereof was determined by EDS (data included in the table).

    TABLE-US-00001 TABLE 1 Precursor Alloy PtRh Alloy PtRu Alloy PtPd Alloy PtIr Reducing 3 mM PtCl.sub.6.sup.2 3 mM PtCl.sub.6.sup.2 3 mM PtCl.sub.6.sup.2 3 mM PtCl.sub.6.sup.2 agent 6 mM Rh.sup.2+ 6 mM Ru.sup.2+ 7 mM Pd.sup.2+ 6 mM Ir(IV) 5M MeOH Alloy RhPt 3:1 Ru Alloy IrPt 5:1 A layer of smooth A rough, cracked A peeling, smooth microparticles with layer layer (FIG. 7d and e) 0.5-2 m diameter (FIG. 7b and c) (FIG. 7a) 3.5M EtOH Alloy RhPt 1:4 Alloy RuPt 1:1 Alloy IrPt 1:1 A layer of A smooth layer A layer of microparticles with ZnSO.sub.4 blocked microstructures 1-4 m diameter (FIG. 7g) ZnSO.sub.4 blocked having slightly rough (FIG. 7h) surface (FIG. 7f) 2.6M isopropanol Alloy RhPt 2:1 Ru Alloy PdPt 3.5:1 Alloy IrPt 10:1 A layer of smooth A thin layer or Ru; A rough layer A layer of microparticles with cracked; ZnSO.sub.4 (FIG. 7m) microstructures; 2-6 m diameter blocked (FIG. 7k and l) smooth (FIG. 7n and o) (FIG. 7i and j)

    Example 9. Preparation of Platinum-Rhodium, -Ruthenium, -Palladium and -Iridium Alloys on a Kanthal Substrate

    [0072] Alloy platinum-ruthenium and platinum-iridium layers were formed using procedure described in Examples 8 and 9, with a difference that a Kanthal substrate was used as a solid support for the formed layer and different alcoholsethanol and sec-butanolwere used as reducing agents. The table below summarizes the conditions used for alloy plating of the substrate, as well as the properties of the obtained layer. The alloy formation and composition thereof was determined by EDS (data presented in the table).

    TABLE-US-00002 TABLE 2 Precursor Alloy PtRu Alloy PtRu Alloy PtIr Reducing 2 mM PtCl.sub.6.sup.2 5 mM PtCl.sub.6.sup.2 3 mM PtCl.sub.6.sup.2 agent 2 mM Ru.sup.2+ 3 mM Ru.sup.2+ 6 mM Ir(IV) 2M EtOH RuPt 1:2 RuPt 1:6 A smooth layer A smooth layer (FIG. 8a and b) 1.5M sec-ButOH Alloy IrPt 1:1 A layer having a rough surface (FIG. 8c and d)

    Example 10. Platinum Layers on PET and PP Substrates Obtained Using Ethanol

    [0073] Platinum layers were obtained on PET and PP substrates, as described in Example 2. However, ethanol was used as a reducing agent instead of 2-propanol. Metallic silver shine coating of was obtained. FIG. 9 presents a photograph of platinum deposits on PET and PP substrates.

    Example 11. Deposition of Platinum Layers on Platinum Substrates Using Different Reducing Agents

    [0074] The influence of different reducing agent on the deposit properties was investigated. Therefore, platinum layers on platinum substrates using different reducing agents were obtained. Prior to deposition, platinum electrodes were flame annealed and quenched in deionized water. Platinum was deposited from plating bath as in Example 1 but different reducing agents were used in concentration 2 M. After 12 hours of deposition cyclic voltammograms have been recorded in 0.5 H.sub.2SO.sub.4.

    [0075] The roughest deposit was obtained in methanol containing bath, which corresponds to the highest current densities at cyclic voltammograms (FIG. 10a).

    [0076] Scanning electron micrographs of the surface of selected deposits are shown in FIGS. 10b, c and d. The material has typical cauliflower-like surface composed of spherical structures of micrometers size. High magnifications recorded for obtained layers show nanocrystalline/amorphous like structuration of the material. On the lower magnification a tendency to stress fractures of the material can be seen (not shown here). Also some tendency to dendrite-like growth of the coating can be observed. The cross-fracture exhibit some internal fibrous structuration of the coating (FIG. 10b) in the growth direction.

    [0077] The sample obtained from a 2-propanol containing bath is much smoother in comparison to other samples. High magnification micrographs exhibit structuration material on the nanometer scale. Some tendency to fracture can be seen, however their number is much smaller. Also, their shape suggest higher plasticity of this coating. Most likely, some of fractures that can be seen are related to the stresses in the base (substrate) material. Cross-fracture of the sample exhibits no tendency to internal structuration of the coating.

    [0078] Morphology of the sample obtained from 2-buthanol is shown in FIG. 10c. The surface of the deposit is rather smooth. Alike the sample obtained with methanol, some nodular structures of micrometer scale can be seen, but with much lower number. The cross-fracture exhibit no internal structuration of the material. All three samples highly mimic the morphology of the base support. Moreover, even when fractured, the deposits remain adhesive to the substrate material (FIG. 10b). The defects of the coatings can be eliminated by use of additives in the process of metallization or slight changes of physical parameters of the process (i.e. temperature).

    Example 12. Mechanical Properties of Platinum Layers on PET, PP and Nafion Substrates

    [0079] Platinum coated substrates of PET, PP and Nafion obtained in Examples 2 and 5 have undergone a mechanical stress test. All the platinum coated substrates were bent, stretched and twisted manually. After the test all substrates were examined with respect to platinum coating integrity. No changes, such as cracks or peeling, of the deposited layers were observed. The fact that the platinum layers remained intact during the mechanical stress test shows a significant integrity and a very good adherence of the deposited platinum layer to the polymer material substrate.

    Example 13. Electrochemical Properties of PGM Deposit Layers on Gold, Kanthal, and Platinum Substrates

    [0080] Electrochemical properties of PGM deposit layers on gold, Kanthal and platinum substrates were investigated. In one of the experiments oxidation of ethanol was carried out using the deposit-substrate assemblies obtained in Examples 1-11.

    [0081] Exemplary results are shown in FIG. 11, which presents voltammograms recorded in 0.5 mol dm.sup.3 H.sub.2SO.sub.4 and 0.5 mol dm.sup.3 ethanol at PtIr alloy deposits obtained using different reducing agents: greyethanol; blackbutanol. The voltammograms were recorded at the scan rate of 5 mV s1 and the currents were normalized to geometric area. As shown in FIG. 11, the electroless deposited layers have been found to be very active towards ethanol oxidation in terms of both the onset potential of ethanol oxidation and the overall voltamperometric current. The most active layers were deposited by using ethanol and butanol as reducing agents. These reducing agents, as described above, enhance significantly surface roughness, which in turn increases the oxidation currents.