Spinel-type ternary ferrites with composition NiFe2-xCrxO4 (0 <= x <= 1) were synthesized by a precipitation method and their physicochemical and electrocatalytic properties have been investigated using IR, XRD, BET surface area, XPS, impedance and Tafel polarization techniques. The study indicated that substitution of Cr from 0.2 to 1.0 mol in the spinel matrix increased the apparent electrocatalytic activity of the base oxide towards the O-2 evolution reaction in 1 M KOH at 25 degrees C. The apparent electrocatalytic activity of the oxide with 0.8-1.0 mol Cr was found to be the greatest among the present series of oxides investigated. It is noteworthy that the electrocatalytic activity of the oxide with x = 0.8-1.0 was also greater than those of other spinel/perovskite O-2 evolving electrocatalysts reported in literature. (c) 2006 Elsevier Ltd. All rights reserved.