In this investigation crystalline ruthenium dioxide square nanorods have been grown on a variety of substrate surfaces and were used as the cathodes in a system to electrolyze an aqueous solution of KOH. Gaseous hydrogen was produced at the cathode and oxygen at the anode. The voltage measured at the cathode relative to the solution, and that across both electrodes was found to be dependent on the cathode material used, specifically the substrate material and the density and nature of a RuO2 nanorod coating. The formation of a double layer on the nanorod surface was proposed to render the production rate of hydrogen, dependent on total interfacial area alone and not on the geometric shape of the nanorods themselves. At a current density of 20 mA/cm(2), the operating efficiency of the RuO2 nanorod cathode cell was found to be 1.7 times that obtained for a cathode electrode fabricated with a simple thin film of RuO2. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.