Abstract: Ti/RuO_2+TiO_2 and Ti/SnO_2+CuCo_2O_4 anodes were used to study oxygen evolution in alkaline solutions and to compare the kinetics on both electrodes.On both electrodes the existence of two Tafel regions are confirmed. At low cd's ψ/lgi=2.303RT/(1+β)F and at high cd's it is 2.303RT/βF.On Ti/SnO_2+CuCo_2O_4 electrodes the reaction order with respect to α_(OH)- is 1 in the/low cd region. For the high cd region the reaction orders are 0.33 and 1 in concentrated alkaline and dilute alkaline solutions respectively.
On Ti/RuO_2+TiO_2 electrodes, the reaction order with respect to a_W a_(OH~-) is 1 in the low cd region. For the high cd region, the reaction order with respect to a_W is 1 in concentrated alkaline solutions, and the reaction order with respect to a_(OH~-) is 0.1~0.5 in dilute alkaline solutions.
The kinetic data obtained show that the rate determing stept of anodic evolution of oxygen are
RuO_2·OH_(ads)+H_2O→RuO(OH)~+_3+e
and (SOH)~(n+)_(ads)→(SOH)~((n+1)+)_(ads)+e
on Ti/RuO_2+TiO_2 electrode and Ti/SnO_2+CuCo_2O_4 electrode, respectively.