Electrochemical measurements were carried out in a three-electrode configuration using a Gamry electrochemical workstation (Interface 1000E) setup in PECC-2 cell from Zahner Elektrik GmbH & Co. KG. A platinum wire was used as a counter electrode and Hg/HgO (1 M KOH) as a reference electrode. All measurements werere carried out in purified 1 M KOH. Before measurements, the Hg/HgO was calibrated by an SHE (HydroFlex, Gaskatel). The cyclic voltammetry (CV) measurements were performed in 1 M KOH at a scan rate of 100 mV/s with the potential from +1.0 to +1.5 V (vs. RHE) were used to activate thin films. Each sample was subjected to four OER activation processes, namely 10 CV, 200 CV, 500 CV, and 1000 CV. After each activation process, we carried out additional 5 CVs between +1.0 V to +1.8 V vs RHE to obtain the OER performance of the film. Electrochemical impedance spectroscopy (EIS) tests were measured at a potential of +1.7 V (vs RHE) within the frequency range of 100 kHz to 1 Hz. The electrochemically active surface area (ECSA) was determined by double-layer capacitance measurements. Specifically, testing CV in the non-Faradaic region around +1.10 V vs at different scan rates (0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, and 0.30 V s -1 ).