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

Abstract

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 has unique and exploitable physical and chemical properties such as corrosion resistance, thermal stability and catalytic activity for various chemical reactions. This noble metal has been widely used in various fields, functioning as catalyst, especially in autocatalysis and fuel cells, as a sensor material and as an electrode material. Electroless deposition of nanostructured platinum for application as an electrocatalyst has also been studied.2,3 However, there are few reports in the scientific literature on the electroless plating bath itself. This may be because electroless deposition of platinum is more difficult to control than that of other noble metals such as gold or palladium. 4 Electroless plating has been used to functionalize the surface of a material and has the potential to enable fabrication of many kinds of device. Therefore a deeper understanding of electroless platinum plating may provide fabrication tools for applications not currently feasible.Studies on electroless platinum deposition or plating baths often utilize hydrazine as the reducing agent. 5,6 The platinum deposits obtained from hydrazine plating baths had excellent purity, however, aside from the discernable odor, hydrazine has been proven harmful to the human body.7 Alternatively, autocatalytic platinum plating with sodium borohydride (SBH) as a reducing agent has been reported. 8,9 In these studies, sulfur compounds such as rhodanine (Figure 1) 8 and thiols like trithiocyanuric acid 9 had been used as stabilizers of the plating bath. However, the stabilization mechanism of the sulfur compounds and identification of effective structures and optimal parameters remains unclear. ...

Green synthesis of gum arabic platinum nanoparticle: Electrochemical sensor application for glyphosate detection

“…The peak that appeared at 39.5° is characteristic of (111) peak of zerovalent Pt with a face centred cubic (fcc) structure. The other diffraction peaks with 2 θ values of 45.8 and 86.9 correspond to the major reflections of crystal planes (200) and (220), respectively, which were in consistence with the nanoscale features of the platinum nanowheels reported in the literature 25–27 …”

“…The other diffraction peaks with 2θ values of 45.8 and 86.9 correspond to the major reflections of crystal planes (200) and (220), respectively, which were in consistence with the nanoscale features of the platinum nanowheels reported in the literature. [25][26][27] The structural characterization of GA and platinum nanoparticles decorated inside the GA network confirm the formation of the GA-Pt nanoparticles. However, critical parameters in nanoparticle synthesis, which are the NPs shape and dispersion, should be determined.…”

Electroless Metallization of the Elements: Survey and Progress

“…Increased H 2 evolution in the BH 4 – bath leading to H 2 incorporation into the Pt suppresses crystal growth and promotes grain boundary formation that accounts for the differences. Additional work by the same group examines the effects of various sulfur compound additives on the EL Pt bath stability, as inhibitors of Pt deposition, and the nature of the Pt deposits. The sulfur compounds inhibit BH 4 – oxidation depending on their chemisorption and steric abilities, which correlates with bath stability and deposition rates.…”

Electrodeposition of High-Functional Metal Oxide on Noble Metal for MEMS Devices

“…The largest TiO 2 aggregate particle size was found at approximate 0.7 μm. When size of the TiO 2 aggregate (or the Ni 2+ -TiO 2 complex) particle reaches a critical size, a phenomenon named steric obstruction takes place to affect inclusion of the particles [46][47][48][49][50][51][52][53]. Steric obstruction is unfavorable for the inclusion as shown in Figure 12(c).…”