Electroreductive Formation of Di‐ and Polysilanes

Hengge, E.; Jammegg, Ch.

doi:10.1002/9783527620777.ch5

Cited by 1 publication

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“…This technique offers a number of advantages over the sacrificial metal anodes including mild electrode passivation, minimal physical damage to the anode function, easy removal of a useful gaseous byproduct ͑HCl͒, and simplified product purification. Hengge's group 9,13 had constructed a hydrogen anode in which H 2 is admitted through a porous graphite rod electrode coated with Pt or Pd, and reported on partial electropolymerization of Me 2 SiCl 2 into polydimethylsilane ͓͑SiMe 2 ͔ n ͒. However, this electrode uses a large amount of noble metals…”

Section: ͓1͔mentioning

confidence: 99%

Electrosynthesis of Oligo- and Polysilanes Using a Modified Gas Diffusion Hydrogen Anode

Wang

Yuan

Cabasso

2006

Electrochem. Solid-State Lett.

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A modified gas diffusion hydrogen anode ͑GDHA͒ was developed for electropolymerization of dichlorosilianes. This GDHA consists of three layers: an H 2 dispersion layer made of a fine glass frit, a Teflon-bound electrical conductive carbon layer, and a Pt/carbon catalyst layer. The performance of this H 2 electrode configuration, having different Pt loadings, was evaluated by electropolymerizing MePhSiCl 2 at different monomer concentrations, current densities, and supplied electricities. The modified hydrogen anode is reported to yield polymethylphenylsilane with Mw = ϳ11000. The product yield, using this hydrogen electrode, approaches 99% ͑i.e., oligomer + polymer͒.Electrosynthesis of polysilanes that are precursors to silicon carbide ceramics 1 and imaging materials for microlithography 2,3 is an alternative method to the conventional Wurtz-coupling polymerization that is catalyzed by molten alkali metals. Electropolymerization is initiated by the electroreduction of organodichlorosilanes, which was studied in detail using a variety of cyclic voltammetric techniques in this laboratory 4 and by Jouikov. 5 Electropolymerization involves electroreductive polymerization of dichlorosilanes on the cathode, with chloride ions released simultaneously. Commonly used anodes, 6-12 such as Mg, Al, Ag, Hg, and Cu, are electrochemically oxidized to the corresponding metal ions during electropolymerization. Thus, they are often referred to as sacrificial anodes. The resulting chloride salts, MCl n , have limited solubility in the organic reaction mixture ͓1͔Subsequently, the salt deposition on the electrodes leads to severe electrode passivation, although sonication and/or alternation of electrode polarity 7 can reduce the passivation, but adds to the complexity of electropolymerization system configuration. Additionally, the gradual consumption of the anode during the course of electropolymerization alters the uniformity of current density distribution.A hydrogen anode technique, where Pt/C electrode catalytically oxidizes hydrogen molecules to protons, was considered as a valuable method to replace the sacrificial metal anode ͑Eq. 2͒. This technique offers a number of advantages over the sacrificial metal anodes including mild electrode passivation, minimal physical damage to the anode function, easy removal of a useful gaseous byproduct ͑HCl͒, and simplified product purification. Hengge's group 9,13 had constructed a hydrogen anode in which H 2 is admitted through a porous graphite rod electrode coated with Pt or Pd, and reported on partial electropolymerization of Me 2 SiCl 2 into polydimethylsilane ͓͑SiMe 2 ͔ n ͒. However, this electrode uses a large amount of noble metals ͓2͔In preliminary electropolymerization with a hydrogen anode, we found that the low performance of a hydrogen electrode originates from the poor distribution of hydrogen in the Pt coated porous graphite surface. This call for modification of the hydrogen electrode led to the construction of an anode that has a low Pt loading, high electrode efficiency...

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Section: ͓1͔mentioning

confidence: 99%