Cobalt and Nitrogen Co-Doped Tungsten Carbide Catalyst for Oxygen Reduction and Hydrogen Evolution Reactions

We have serendipitously facile developed a dual-performing electrocatalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) by co-doped cobalt and nitrogen on tungsten carbide matrix. Its improved ORR and HER activities in 0.1 M KOH were confirmed using a thin-film rotating ring-disk electrode (TF-RRDE) and electrochemical impedance spectroscopy (EIS). The exchange current density and Tafel slope obtained from EIS data for HER are 1.6 x 10 (2) mAcm (2). and similar to 43 mV dec (1) respectively, suggesting Volmer-Heyrovsky mechanism for HER. In addition to its good durability for both cathodic processes, catalyst shows a 4-electron transfer process for ORR, excellent tolerance towards methanol oxidation, and low H2O2 formation (similar to 3.0%). At half-wave potential of 0.8 V, no significant degradation was observed after 10,000 (0.65 - 1.0V) potential cycles in oxygen saturated medium. A catalyst of such benign properties is highly indispensable for energy conversion systems. (C) 2015 Elsevier Ltd. All rights reserved.