Figure 4. (a) Double layer charge capacitance in CO2-saturated 0.1 M KHCO3 electrolyte and (b) OHadspeaks from LSV curves obtained in Ar-saturated 0.1 M KOH electrolyte of commercial Cu NP, pristine CuO NS, Cu-30, and Cu-100. The inset image shows a magnified section of the (111) shoulder peak between 0.42-0.53 VRHE.