Catalytic oxide electrodes of Ru /Ti, Ru-Sn-/Ti, and Ru-Sn-Ti-/Ti effective in destroying refractory organics in aqueous waste were studied in terms of material and electrochemical properties. The portion of non-stochiometry, RnOx (0 < x < 2) and chloride-bonded Ru within the Ru-based oxide were evaluated by deconvolution of XPS of the oxide with a change of sintering temperature. RuOx mostly existed around 450 degreesC, and disappeared at 600 degreesC. The component of chloride-bonded Ru decreased nearly linearly from 350 to 600 degreesC. The non-stochiometry resulted from the incomplete decomposition of metal chloride in the precursor solution. The existence of non-stochiometry was confirmed to have a close relation to the electrochemical activity of the oxide electrode. The segregation phenomena of Sn and the existence of chloride in Ru Sn Ti-/Ti oxide after sintering were confirmed by AES, XPS, and EPMA. (C) 2001 Elsevier Science Ltd. All rights reserved.