Elucidating the Mechanism of Oxygen Evolution Reaction on Nanostructured Copper-Based Catalysts

In water splitting processes, the oxygen evolution reaction (OER) is one of the main kinetic control steps that should be triggered by high-efficiency catalysts. A series of Cu-based catalysts are considered potential candidates. This work provides a simple and effective strategy for fabricating large-scale copper-based catalysts by anodization on a copper foil at room temperature in a KOH solution. The representative petal-shaped CuO and Cu(OH)₂ nanorods are obtained. The corresponding surface areas are 0.0197 and 1.966 m²/g, respectively. The surface wettability of Cu(OH)₂ is lower than that of CuO. The catalytic performance is studied by linear sweep voltammetry (LSV). The results show that the potential of the OER for CuO at 10 mA/cm² is 1.67 V, which reduces by 130 mV compared to Cu(OH)₂. The CuO could keep 10 mA/cm² after a 1 h chronoamperometry test, which is about 3 times higher than that of Cu(OH)₂. To verify the distinguishing catalytic difference between CuO and Cu(OH)₂, in situ Raman spectra have been recorded. Inspiringly, the Cu^III active specie at 603 cm^–1 is captured during the OER process on CuO instead of Cu(OH)₂. The related mechanism has been discussed in detail.