Rutile-type Ru1-xVxO2 nanoparticles possessing high surface area were prepared by a polymerizable-complex method and its electrochemical supercapacitor behavior was studied. X-ray diffractometry, energy-dispersive X-ray analysis, and N-2 adsorption/desorption measurements were used to characterize the structure of the products. The electrochemical supercapacitor behavior of thick and thin films was studied by cyclic voltammetry in various acidic, neutral, and alkaline electrolytes. Ru1-xVxO2 exhibited extremely enhanced supercapacitive properties compared to pure RuO2. The highest surface redox activity was achieved with an acidic electrolyte. Ru1-xVxO2 showed negligible surface redox activity in neutral electrolytes. (c) 2006 Elsevier B.V. All rights reserved.