Hydrogen Evolution-Directed Electrodeposition of a Cobalt Selenide/Cobalt Oxide Electrocatalyst for the Hydrogen and Oxygen Evolution Reactions

As more emphasis is placed on renewable energy worldwide, the electrochemical splitting of water has attracted considerable attention. Herein, a simple and cost-effective electrocatalyst was studied for both the hydrogen and oxygen evolution reactions. The electrocatalyst consisted of an electrodeposited cobalt diselenide/cobalt oxide composite, which was fabricated from an aqueous solution containing cobalt and selenium salts on a glassy carbon substrate. The optimal deposition conditions were found to be a fixed potential at -1.2 V vs Ag/AgCl for 400 s. At this relatively low potential, the electrodeposition process is accompanied by the hydrogen evolution reaction, resulting in a hierarchical, flower-like morphology. The electrochemical active surface area was calculated to be 89 cm2 in 1.0 M KOH and 72 cm2 in 0.5 M H2SO4. This electrocatalyst facilitated the hydrogen evolution reaction in both KOH and H2SO4 solutions, with overpotentials of 305 and 205 mV at 10 mA cm-2, respectively. Similarly, good oxygen evolution activity was achieved in KOH. The electrocatalyst demonstrated good stability over a 24 h period, with evidence of improved oxygen evolution activity following the stability studies.