Importance of Cobalt-Doping for the Preparation of Hollow CuBr/Co@CuO Nanocorals on Copper Foils with Enhanced Electrocatalytic Activity and Stability for Oxygen Evolution Reaction

In this work, we demonstrate a simple electrochemical approach to convert copper foil into a cost-effective and stable cobalt-doped hollow-structured CuBr@CuO electrocatalyst with high surface porosity for oxygen evolution reaction (OER). First, a thin layer of surface copper atoms of the foil was converted to γ-CuBr nanocorals (NCs) by dissolution and in situ deposition in a bromide medium. Then, the CuBr NCs were doped with Co utilizing the high ionic mobility of Cu+ in the γ-CuBr structure through cation exchange and dissolution reactions. During the Co-doping process, the surface γ-CuBr was converted to Cu2O, leading to the formation of CuBr/Co@Cu2O NCs. CuBr/Co@Cu2O NCs were then converted to CuBr/Co@CuO hollow NCs (h-NCs), with high surface roughness and high stability by three linear sweep voltammetry (LSV) scans in O2-saturated KOH solution (0.1 M) over a potential range of 1.2-1.7 V (vs RHE). The h-NC was not formed without Co-doping of γ-CuBr. The as-formed CuBr/Co@CuO h-NCs exhibit an overpotential of 270 mV with a current density of 10 mA cm-2 and a Tafel slope of 66 mV dec-1 for OER as a result of having high electrochemically active surface area and synergistic catalytic Co and CuBr@CuO nanostructures.