Nanoporous molybdenum oxynitride has been synthesized and studied for the first time as an oxygen reduction catalyst in a 0.1 M KCl aqueous solution (pH 5.6). Modified electrodes containing the oxynitride catalyst, TIMCAL Super P (TM) Li carbon as a conducting carbon additive and polyvinylidene fluoride as a binder were prepared, and the ratios of the different components were studied in detail to yield the optimum composition. The oxygen reduction reaction mechanism has been analyzed by the Koutecky-Levich equation using a rotating disk electrode and is in concordance with a four-electron pathway for the molybdenum oxynitride catalyst. Rotating ring-disk electrode experiments have further confirmed the electrocatalytic performance of such oxynitrides toward oxygen reduction, determining an average production of H2O2 of just 2.35%. Finally, we have also compared the performance of vanadium and tungsten oxynitrides under the same conditions as the optimal molybdenum oxynitride. (C) 2013 Elsevier Ltd. All rights reserved.