Abstract: The surface compositions and valence band structures of RuO₂electrodes prepared at different sintering temperatures have been studied by means of XPS and UPS. It was shown that O/Ru atomic ratio, I (σ + π)/I(π^*) intensity ratio and the π^* binding energy increase with the increasing of the sintering temperature, indicating the decreasing of the density of d-electron beneath Fermi level and the difficulty of RuO₂to be oxidized to activation intermediate RuO₄.On the basis of the facts above we suggested that the active sites of RuO₂etectrode for oxygen evolution are oxygen-deficiency rather than RuO₃· The fact that the electrocatalytical activation of RuO₂electrode decreases as the sinterering temperature increasing was also explained.

Key words: RuO₂Electrode, Oxygen-deficiency, Electro-catalysis, XPS,UPS,Oxygen evolution