Wojciech Grochala
University of Warsaw, Poland
Title: Efficient electrosynthesis of silver(II) salts
Biography
Biography: Wojciech Grochala
Abstract
The standard redox potential of the Ag(II)/Ag(I) redox pair reaches some 2 V vs. NHE, which renders Ag(I) notoriously difficult to oxidize in aqueous environment due to preceding oxidation of water. However, Ag(II) species may easily be obtained in non-aqueous media, and in some they may be sufficiently short-lived to enable preparation of genuine Ag(II) salts. Here we will discuss our recent attempts to understand electrochemistry of Ag(II) in anhydrous H2SO4 [1,2] and HF [3]. It turns out that oxidation of Ag(I) in H2SO4 leads to [Ag(II)(HSO4)2(H2SO4)2] complex partly soluble in the solvent; the formal redox potential in 30% oleum reaches +2.9 V vs. NHE, which is the largest experimentally determined value for fluorine-free system. Upon prolonged electrolysis black residue of Ag(II)(SO4) semiconductor precipitates from the solution.
Similar experiments carried out in anhydrous HF lead to formation of AgF2. This compound is currently considered to be the only known analogue of parent compounds of oxocuprate superconductors and intense research is carried out worldwide in attempts to dope this system. Success of preparative elecrosynthesis of AgF2 opens new route towards doped and mixed-valence systems which are of immense important for solid state physics. Further efforts in this direction might lead to expansion of the family of the Ag(II)/F systems known to date.