Electrochemical oxidation of brass in electrolytes with different viscosities

The effect of the glycerol addition to 1 M NaOH aqueous electrolyte used for the passivation of copper on the morphology, crystalline structure as well as composition was explored for the first time. It was revealed that the morphology of the obtained material depends strongly on the content of the glycerol in the electrolyte, the duration of the passivation, and to a lesser extent on the applied potential in the studied range. Moreover, even a small addition (5 vol.%) of glycerol changed significantly the composition of the obtained passive layer. In the absence of glycerol, barrel-like structures composed mostly of crystalline Cu(OH)2 were observed. After the addition of glycerol, the formation of the passive layer with spiked petals, composed mainly of crystalline ZnO and amorphous Cu2O, was detected. Moreover, the used potential had an influence on the macroscopic behavior of the samples - for samples prepared at 100 mV vs. Hg|HgO - poor adhesion to the substrate surface after sample drying was noted. Significantly improved macroscopic stability of passive layers obtained at the applied potential of 300 mV was observed. Such samples, prepared at selected glycerol concentrations were used for electrochemical carbon oxide reduction reaction studies to explore one possible application of the presented material.