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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 Codoping process, the surface γ-CuBr was converted to Cu 2 O, leading to the formation of CuBr/Co@Cu 2 O NCs. CuBr/Co@Cu 2 O 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 O 2 -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.

The electrochemical behavior of arsenic(III) and indium(III) is investigated in the ethaline deep eutectic solvent (a mixture of 1 mol eq. of choline chloride and 2 mol eq. of ethylene glycol) using As 2 O 3 and InCl 3 as precursors. Cyclic voltammetry of ethaline solutions containing individual As(III) and In(III) reveals that the thermodynamic deposition potential of As is more negative than that of In in ethaline, in contrast to what has been observed in aqueous solutions. When In(III) is mixed with As(III), the reduction of In(III) shifts positively while the reduction of As(III) shifts negatively with respect to that of individual solutions. Co-deposition of In-As is attempted using potentiostatic electrolysis on Cu and Ni substrates, respectively. The electrodeposited films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and X-ray powder diffraction (XRD). The As/In atom ratio in the obtained deposits increases as the deposition potential gets more negative. Crystalline InAs film can be obtained from the ethaline solution contains a As(III) concentration higher than that of In(III). However, the co-deposits turn into amorphous once the As content in the deposits exceeds that of In.