Selective electrocatalysis of anodic oxygen-transfer reactions at chemically modified, thin-film lead dioxide electrodes.

摘要

The strategy to modify PbO(sub 2) electrodes for electrocatalysis of oxygen-transfer (O-t) reactions is to incorporate spatially separated catalytic sites into the PbO(sub 2) surface. The rate of OH radical formation is promoted at these sites, as is the rate of the O-t reaction, for the latter was demonstrated to be proportional to the former. Chemically modified PbO(sub 2) is electrodeposited by addition of Bi(sup 3+), As(III), or Cl(sup (minus)) to the Pb(sup 2+) plating bath. The electrochemical stability and catalytic activity of the Bi-doped PbO(sub 2) (Bi-PbO(sub 2)) increase with increased Bi/Pb atomic ratio in the mixed oxide which were determined with x-ray photoelectron spectroscopy. Microcracked, ultra-thin films of Bi-PbO(sub 2) were found at Au, Pt, GC, and Ti electrodes after consecutive deposition and stripping of the thick oxide films. The surface of pure PbO(sub 2) can be modified by Bi(sup 3+), As(V), and Cl(sup (minus)) by electroadsorption. The adsorption method to modify PbO(sub 2) is fast and efficient for screening new catalysts. An O-t mediation mechanism was proposed for the electrocatalysis observed at the chemically modified PbO(sub 2). 31 refs., 12 figs.