Carbon black modified with silver and low concentration of palladium as effective catalysts for electroreduction of oxygen in alkaline solutions

The properties of catalysts for the electrochemical reduction of oxygen synthesized using Vulcan XC-72 carbon black, modified with silver and palladium using the borohydride method, were studied. The palladium content was in the range from 1 to 4% by the mass. The catalytic properties of the following catalyst samples were studied: Ag(10%)/C, Pd(4%)–Ag(10%)/C, Pd(2%)–Ag(10%)/C and Pd (1%)–Ag(10%)/C. Their electrocatalytic activity in the oxygen reduction reaction was studied by linear voltammetry using a rotating disk electrode ( RDE ) in a 0.1 M KOH solution air-saturated. The main kinetic parameters of the reaction (limiting currents, number of electrons) were calculated using the Koutecky-Levich equation, also the effect of the palladium concentration on the catalyst activity is shown. The presence of active sites on the catalyst surface was estimated by cyclic voltammetry in a de-aerated 0.1 M KOH solution. A synergistic effect of palladium and silver has been observed for the Pd(2%)–Ag(10%)/C catalyst, which enhances the efficiency of the oxygen reduction process.