Electroless Platinum Research Articles

Electroless platinum and palladium deposition over alumina coated stainless steel plates and their catalytic activity for hydrogen mitigation in severe nuclear accidents

This work focused on platinum and palladium-based autocatalytic plates, which used to remove hydrogen. The six sandblasted stainless steel plates were coated with platinum and palladium metals using the electroless coating method. The three plates A-01, A-02, A-03 were first coated with alumina using the sol-gel dip method, and after that, different ratios of platinum and palladium were deposited on them. The three other plates, B-01, B-02, B-03 (without alumina coated), were coated directly with different ratios of platinum and palladium. The platinum and palladium ratio used for coating these plates were Pt 80%: Pd 20%; Pt 90%: Pd 10%, and Pt 70%: Pd 30. The coating of these plates was characterized using Scanning Electron Microscopy, X-rays Fluorescence Spectroscopy, and their catalytic efficiency was measured by the Passive Autocatalytic Recombiner testing rig method. It was found that the plates coated with alumina using two dipping cycles are suitable for different coating of mixed metals by electroless coating method compared to three dipping cycles. It was observed that the alumina-coated catalytic plates (A-01, A-02, A-03) exhibited excellent catalytic efficiency as compared to those without alumina-coated plates (B-01, B-02, B-03). Furthermore, the catalytic efficiency of A-03 and B-03 is higher than other plates. It was also found that the catalytic efficiency of A-03 is higher than B-03. The best coating ratio is Pt 90%: Pd10%, and alumina-coated plates give excellent results.

Synthesis of nanoporous acicular-mullite ceramic and electroless platinum coating for particulate matter entrapment and catalytic combustion

Crystal-structured acicular-mullite ceramic with high porosity and interpenetrated networks was fabricated for diesel particulate filter (DPF), followed by electroless deposition of platinum (Pt) catalysis throughout ceramic surfaces from an aqueous Pt (IV) solution. The integrated material was characterized and compared with commercial cordierite particulate matter (PM) filter, exhibiting many excellent properties in surface area, porous ratio, and loading capacity for both soot and catalyst. The resulting surface density of Pt nanoparticles attained as high as 8.0 × 109/cm2 due to the 3-dimensional architecture, while maintaining a pore ratio, 63.72%, relative to 52.60% in its counterpart. Deposited Pt nanoparticles artfully serve as catalysis for combustion of carbon soot, potentially implemented for diesel engine filter, reducing the particulate matter emission for environmental protection. The catalytic performance was evaluated by a regular thermal gravity analysis (TGA) measurement, showing that the significant drop of soot conversion temperature, and soot convert rate could be further improved by co-precipitating CeO2 catalyst additive. This material, thereby, could readily adapt itself into large-scale production.

Electroless Platinum Deposition Using Co3+/Co2+ Redox Couple as a Reducing Agent.

In the present work, the kinetics of electroless deposition of Pt, using a cobalt ion redox system (Co3+/Co2+) as a reducing agent, has been investigated. The deposition rate of Pt depends on the pH, concentration of reactants, and temperature. The deaeration and bubbling of the plating solution with argon play an essential role. It was found that 0.11 mg cm−2 of Pt films could be deposited on the surface of a roughed glass sheet in one hour without replenishing the solution. Additional data have been obtained on the grounds of electrochemical quartz crystal microbalance experiments. The bubbling (agitation) of the electroless Pt plating solution with argon during the deposition of Pt results in a higher deposition rate and is ca. 3 µg cm−2 min−1. The Pt deposition rate is far less, and is as low as 0.14 µg cm−2 min−1 when the electroless Pt plating solution is not bubbled with argon during the deposition of Pt.

Comparative study on physical and electrochemical characteristics of thin films deposited from electroless platinum plating baths

Physical and electrochemical properties of deposits obtained from two types of electroless platinum plating bath were investigated. One bath contained hydrazine as the reducer and lead monoxide as the stabilizer (HYD bath), and the other contained sodium borohydride (SBH) as the reducer and sodium thiosulfate as the stabilizer (SBH bath). The deposit obtained from the SBH bath had a high electric resistivity (6.0×10−5Ωcm), large tensile stress (421MPa at 0.3μm thickness) and rough surface (Ra=19.2nm) compared to HYD bath. Approximately 5 times more gas emission from the SBH bath was confirmed during electroless plating than HYD bath. The hydrogen emission during plating affected the physical properties of the resulting deposit and explained the rougher surface of platinum films from the SBH bath. The CV measurement using the deposits as the working electrode also correlated with surface area. Less than 0.5wt% of sulfur inclusion deriving from the stabilizer into the SBH bath deposit did not affect the surface roughness or electrochemical properties.

Comparative Study of Electroless Platinum Deposition Using Multivalent Metal Ions or Hydrazine As Reducing Agents

Two new type electroless plating processes for deposition of continuous platinum layer are proposed and compared with known process of electroless platinum daeposition using hydrazine as reducing agent. In this study investigation of the kinetics of electroless Pt deposition, using reducing agents such as Co(II)/Co(III) and Ti(III)/Ti(IV) redox systems, is presented. The Pt layers were deposited on the copper or nickel surfaces. The morphology of Pt layers deposited using different reducing agents was investigated by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of deposition rate of Pt was investigated by means of the Electrochemical Quartz Crystal Microgravimetry (EQCM). It was found that the deaeration of the electroless Pt plating solutions with argon, using Co(II)/Co(III) or Ti(III)/Ti(IV) redox systems as reducing agents, results in higher deposition rates of Pt. When using Co(II)/Co(III) redox system as a reducing agent, the rate of electroless deposition of Pt is ca. 0.3 µg cm-2 min-1 when using Ar-deaerated plating solution, whereas the one in non-deaerated plating solution is significantly lower, e.g. 0.02 µg cm-2 min-1. When, using the Ti(III)/Ti(IV) redox system as reducing agent, the Pt deposition rate in Ar-deaerated plating solution is higher compared with that using CoII)/Co(III) redox couple. It should be noted that the obtained Pt layers deposited on the surface of Cu using Co(II)/Co(III) or Ti(III)/Ti(IV) redox pairs as reducing agents are continuous and compact. The kinetic data of the mentioned reactions is discussed and compared with that obtained using hydrazine as reducing agent. Acknowledgment This research was funded by a Grant (No. TEC-06/2015) from the Research Council of Lithuania.

Stabilization of an Electroless Platinum Plating Bath Using S-Bearing Additives

Moderation of an electroless platinum plating bath by thiol, thioether, disulfide, thiocarbonyl, thiosulfate and sulfide compounds was investigated. The inhibitory effect of stabilizers on catalyzed anodic oxidation of the reducing agent used, sodium borohydride, on platinum surfaces was electrochemically characterized by linear sweep voltammetry. Catalytic oxidation inhibition was found to correlate with chemisorption dynamics to catalytic sites on the platinum surface and the steric structure of the sulfur in the compound. Evaluation of the compounds as moderators in electroless plating revealed that the deposition rate and bath stability correlated with the sodium borohydride oxidation inhibition character. Tiopronin had a moderate inhibitory effect on catalytic sodium borohydride oxidation and functioned as an effective stabilizer in the electroless platinum plating bath. Based on the correlation, an inhibitor concentration optimization method using anodic polarization curves was established. The dynamics of the electroless plating reaction concurred with electrochemical analysis and was comprehensively described by the mixed potential theory. Using cyclic voltammetry, the deposits had similar electrochemical characteristic to that of pure polycrystalline platinum, although less than 0.5 wt% sulfur inclusion was confirmed by elemental analysis.

Platinum nanoparticle decorated silicon nanowire arrays for photoelectrochemical hydrogen production

Wafer-scale high density aligned p-type silicon nanowire (SiNW) arrays decorated with discrete platinum nanoparticles (PtNPs) have been fabricated by metal assisted electroless etching followed by an electroless platinum deposition process, and systematic investigations of photoelectrochemical behavior of Pt/SiNW were also reported in this study. Coating of PtNPs on SiNW sidewalls yielded a more positive onset potential (Vos), which enhances the photoelectrochemical hydrogen generation performance of the photoelectrodes, though excessive PtNPs deposition leads to a decreased photocurrent. Additionally, we have demonstrated that the photoelectrode consisting of longer SiNWs yielded a higher limiting current. However, when the length of SiNWs was increased further to >4 μm, the limiting current dramatically reduced, which is presumably because an increased interface recombination and scattering resulting from the increased surface area of SiNWs begin to play a dominant role. The results demonstrate Pt/SiNW to be a promising hybrid system for photoelectrochemical water splitting, and device performance may be further improved via optimal conditions of PtNPs deposition time and SiNWs length.

Electroless platinum counter electrodes with Pt-activated self-assembled monolayer on transparent conducting oxide

In this study, electroless Pt films deposited on transparent conducting oxide (TCO)-coated substrates were prepared using a Pt-activated self-assembled monolayer (SAM) and employed as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). First, the mechanism for the formation of Pt-activated SAM on TCO-coated substrate was examined using X-ray photoelectron spectroscopy analyses. Second, the effects of the pH value and bath composition on the surface morphology and electrocatalytic activity were also investigated. After the optimization with the pH and composition of deposition bath, the Pt CE prepared by the optimized bath composition of electroless deposition (ELD) was found to have a lower Pt loading (15.91μgcm−2), a higher specific active surface area (209.71m2g−1) and lower charge-transfer resistance (1.92Ω·cm2) than the sputtered-Pt CE. Thus, the cell efficiency of the DSSC based on the ELD-Pt CE achieved 7.65%, which represented an increase of 12.33% when compared to the sputtered-Pt CE, while the Pt loading was also remarkably reduced (being 14.82% of that of the sputtered-Pt CE).

Optimal Investigation of Electroless Platinum Counter Electrodes for Use in Dye-Sensitized Solar Cells

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Electroless Platinum Counter Electrode for Dye-Sensitized Solar Cells by Using Self-Assembly Monolayer Modification

In this study, a cost-effective and low temperature wet process has been developed for the fabrication of a Pt counter electrode in dye-sensitized solar cells (DSSCs) with superior coating selectivity by means of self-assembly monolayer modification and electroless deposition. Using such Pt counter electrode prepared by our method, it is easy to deposit a Pt thin film under ambient atmosphere and low temperature without a high vacuum chamber and the acceptable charge-transfer resistance of 1.24 Ω cm 2 is obtained. Moreover, the DSSC exhibited improved performance compared to the DSSC with a sputtered Pt counter electrode.

Platinum Nanoparticle Decorated Silicon Nanowires for Efficient Solar Energy Conversion

High-density aligned n-type silicon nanowire (SiNW) arrays decorated with discrete 5-10 nm platinum nanoparticles (PtNPs) have been fabricated by aqueous electroless Si etching followed by an electroless platinum deposition process. Coating of PtNPs on SiNW sidewalls yielded a substantial enhancement in photoconversion efficiency and an apparent energy conversion efficiency of up to 8.14% for the PtNP-decorated SiNW-based photoelectrochemical solar cell using a liquid electrolyte containing Br(-)/Br(2) redox couple. The results demonstrate PtNP-decorated SiNWs to be a promising hybrid system for solar energy conversion.

Depth profiling and stoichiometry of constituents in platinum electroless contacts on CdTe(111) under different pH values

Rutherford backscattering spectrometry was performed using 2 MeV alpha-particles, to characterize electroless platinum contacts on cadmium telluride CdTe(111) crystals, aiming to improve and to understand the structure of the metal electroless chemically deposited. In this paper we have studied the platinum metal contact as well as the interface material-contact. The thickness, the stoichiometry and the concentration profile of platinum, cadmium, tellurium and oxygen present in the surface layers were determined as a function of many parameters, especially the variation trend as function of the chloride solution pH. This work showed the important effect of the crystallographic direction on the growth of Pt on CdTe II–VI semiconductors. Furthermore, the process was more pH dependence at the metalloid Te face than the Cd one.

Morphological selection of electroless metal deposits on silicon in aqueous fluoride solution

Well-defined silver and gold dendrites are prepared on silicon substrates in aqueous fluoride acid solution containing AgNO3 and KAuCl4, respectively. In cases of electroless platinum and copper deposition in fluoride acid solution, no corresponding metal dendrites but platinum microcrystallines and copper granular-crystallines are formed. Our experiments found that the morphological selection of electroless metal deposits is related to the microstructure of etched silicon. A possible template mechanism and affecting factors for the morphological selection of electroless metal deposits are discussed.

Electroless deposition of platinum on titanium substrates

The use of an electroless platinum bath based on chloroplatinic acid and hydrazine for depositing adherent and uniform layers on titanium panels is demonstrated. The conditions were optimised for a new set of additives. The effect of concentrations of platinum metal in the bath on thickness of the deposit was studied. The deposition rates on titanium and gold-plated titanium are evaluated. Dispersed platinum coatings on titanium powder were successfully obtained.

A tin-free catalyst for electroless platinum deposition on polyethylene terephthalate

The metallization of polymer materials has many applications in a range of industries for decorative and=or functional purposes, e.g., nickel plating of ABS plastics in automotive parts [1] and copper plating of polyimides in printed-circuit boards [2]. Electroless deposition has attracted a great deal of interest as an economic means of metallization of polymers. Recently, this technique has been shown to have signi®cant potential for the fabrication of a new generation of electrodes used in implantable medical applications, such as de®brillation, pacing and cardiomyoplasty [3]. Since electroless deposition takes place only on conductors, it is necessary to use a catalyst to seed the insulator surface with catalytic metal particles [1]. Traditionally, a two-step treatment is used in which a SnCl2 solution acts as a sensitizer and a PdCl2 solution as an activator to provide catalytic metallic Pd sites [4]. More recently, a one-step treatment has been introduced using a mixed SnCl2 ± PdCl2 solution to yield Pd±Sn alloy as catalyst centres [5±9]. These activation treatments are normally followed by an acceleration treatment to remove excessive Sn ions which inhibit electroless deposition. Both these methods use tin which is known to be toxic and therefore they are not suitable for medical implants. A new method for the activation of a nonconductor which eliminates the use of tin has been invented by our research group [10]. In this letter, we report the use of this new catalyst for electroless platinum deposition on polyethylene terephthalate (PET) surfaces. Platinum and PET are chosen because of their proven suitability for use in implantable medical devices. The results to be discussed were mostly generated from experiments on PET ®lms which facilitates characterization and testing. Preliminary results from PET ®bres are also brie y discussesd. PET ®lms of 0.1 mm thickness were supplied by Goodfellow and PET ®bres of diameter approximately 22 im were supplied by Akzo Fibres. Unless otherwise stated, all chemicals were supplied by Aldrich or Sigma as laboratory reagents with no further puri®cation. A tin-free catalyst was prepared by dissolving 0.2% (w=v) PdCl2 into dimethylsulphoxide (DMSO), which is referred to as DMSO±Pd catalyst in this report. A reducer was formulated with 4% (v=v) hydrazine in aqueous solution. The electroless deposition bath was a proprietary formulation and it was used as recommended, except for some adjustment of the ammonia concentration. The electroless deposition of Pt on PET using the new catalyst method involved the following four steps, with thorough rinsing in de-ionized water between each step. As-received PET ®lms or ®bres were ®rstly washed in hot detergent solution (NewBon at a strength of 0.1%) for 30 min at 80 8C to remove wax and=or oil residues present on the surface. The cleaned samples were then etched in a hot alkaline bath which consisted of NaOH (100 g ly1) and 0.1% surfactant (proprietary product) for 30 min at 80 8C. The etching provided a rough PET surface for better adhesion through the mechanical interlocking of the Pt coating and the PET substrate. Catalysis was achieved by dipping the PET samples into the DMSO±Pd catalyst for a speci®c time and then dipping the samples into the reducer for 1 min, with both the catalyst and the reducer maintained at room temperature. The catalysed samples were immersed into a pre-heated electroless deposition bath at the recommended temperature of 60 8C for the required deposition time. The above cleaning and etching steps were carried out with vigorous mechanical agitation, whereas the catalysis and electroless deposition were conducted with gentle agitation. In addition, some selected ®bre samples, treated under slightly different etching conditions, were electrolessly plated using either the new catalyst or the traditional mixed Sn±Pd catalyst to give a comparative study on the adhesion between the Pt coatings and the PET substrate.

Atomic Force Microscopy Study of the Silicon Doping Influence on the First Stages of Platinum Electroless Deposition

The first stages of platinum electroless deposition on (100) Si from hydrogen fluoride solutions are studied by tapping mode atomic force microscopy (AFM), transmission electron microscopy (TEM), and x‐ray photoelectron spectroscopy (XPS). Tapping mode AFM and TEM provide a morphological characterization of the samples, while XPS accounts for the compounds present on the surface. During immersion in an aqueous HF solution containing a platinum salt, platinum nucleates on the silicon substrate while the surface is etched. The deposited nuclei are polycrystalline, highly pure, and strongly silicidated at room temperature. Metal deposition takes place by means of a redox reaction in which silicon atoms oxidize, supplying the electrons for the metal to reduce. For all substrates, platinum silicide is formed during deposition at room temperature, suggesting a competition between the deposition of pure metal by an electrochemical mechanism and the formation of the silicide by direct reaction. For equal deposition times, more platinum deposits on p‐type substrates than in n+. p‐Type substrates, moreover, undergo a general increase in roughness in the bare silicon areas, while n‐type substrates present a lower and more local etching. This seems to indicate that electroless platinum deposition is somehow hindered on n+ substrates.

小特集／無電解めっきの現状と将来 無電解白金めっき

小特集／無電解めっきの現状と将来 無電解白金めっき