A multifunctional gold doped Co(OH)2 electrocatalyst tailored for water oxidation, oxygen reduction, hydrogen evolution and glucose detection

Abstract

Electrocatalytic reactions are central to many energy and sensing applications and therefore the development of materials that show functionality for more than one reaction are of significant interest. The synthesis of affordable electrocatalysts for the oxygen evolution reaction (OER) involved in electrochemical water splitting, the oxygen reduction reaction (ORR) for fuel cells in energy research and the detection of glucose in the sensor field are of high importance. Herein, we demonstrate the single step electrochemical formation of a gold doped-Co(OH)₂ electrocatalyst on a carbon support which is highly active for the three aforementioned electrocatalytic reactions. The distribution of gold within the Co(OH)₂ film can be controlled by electrochemical potential cycling and was measured by depth-profiling X-ray photoelectron spectroscopy. The optimised Au–Co(OH)₂ films showed enhanced OER/ORR activity in alkaline conditions due to synergy between the materials. This resulted in excellent bifunctional activity for oxygen electrochemistry where a current density of 10 mA cm⁻² for the OER was reached at a potential of 1.55 V and −3 mA cm⁻² was achieved for the ORR via a 4 electron pathway at 0.69 V giving a combined overpotential η_total = η_OER + η_ORR of only 0.86 V in 0.1 M NaOH. In addition, due to the distribution of gold active sites within a Co(OH)₂ framework, the material was also active for the hydrogen evolution reaction as well as being sensitive and selective to glucose detection in the presence of common interfering species.