Catalytic activity of silver colloids on polarographic reduction of oxygen

The catalytic electroreduction of O₂ at DME in the presence of colloidal silver has been studied. Two colloids, characterized by different catalytic activity, have been prepared and tested. The influence of the height of the mercury head, pH, and temperature on both the first and the second wave of the polarographic reduction of O₂ have been investigated. A mechanism, which takes into account the possible adsorption of OH^? ions on the silver catalyst, is proposed for the H₂O₂ decomposition: the experimental points fit the calculated curve of log k_s vs. pH well. Thermodynamic parameters are also derived.