Abstract: The kinetic data related respectively to Co~(3+) anodic formation and O_2 anodic evolution at PbO_2 anode in 3.4 mol·kg~(-1) H_2SO_4+x mol·dm~(-3) COSO_4 (x=0.0501-0.350) and 0.2 mol·dm~(-3) CoSO_4+x mol·kg~(-1) H_2SO_4 (x=1.556-9.110) solutions were obtained by method of resolving the steady-state polarization curve. Steady-state φ～lgi relationships for Co~(3+) anodic formation reaction Tafel slope is close to 2.303RT/βF, whereas for O_2 anodic evolution it is close to 2.303RT/2βF (with β(?)0.5).
It is shown by experiment that the anodic formation of Co~(3+) and O_2 anodic evolution at PbO_2 anode in H_2SO_4 solutions are described by the equations:
i_1(O_2)=k_1a_W~4[Co~(2+)]exp2βφF/RT
i_2(Co~(3+))=k_2a_W[Co~(2+)]~(1.5)expβφF/RT
The experimental results may be explained by adopting the following scheme of electrode reactions
M+Co(H_2O)_6~(2-)+4H_2O→MCo(OH)_4(H_2O)_(2,ad)+4H_3O~++2e
2MCo(OH)_4(H_2O)_(2,ad)+2H_2O→O_2+2MCoO(H_2O)_(5,ad)
MCoO(H_2O)_(5,ad)+2H~+=M+Co(H_2O)_6~(2+)
MCo(OH)_4(H_2O)_(2,ad)+Co(H_2O)_6~(2+)→2Co(OH)_2(H_2O)_4~++M
Co(OH)_2(H_2O)_4~++2H~+=Co(H_2O)_6~(3+)
where M is an adsorption site on the PbO_2 anode.

Key words: PbO₂ anode, Co(II) ion, Co(III) ion