PEC characterization was performed using an SP-200 Bio-Logic potentiostat in a threeelectrode configuration consisting of a photoanode, platinum wire, and Ag/AgCl as working, counter, and reference electrodes, respectively. A 150 W Xe lamp (LOT Oriel) equipped with an AM 1.5 G filter was used as the light source for PEC measurements (calibrated to 1 sun illumination using a standardized Si solar cell). For PEC measurement, 1 M KOH (pH 14) and 0.5 M KPi (pH 7) were used as electrolytes. The produced oxygen of the photoanode was measured by an Inficon Fusion Micro gas chromatograph (Chemlys) with a molecular sieve column (10 m) and a TCD detector. Argon was used as the carrier gas. The operation pressure was between 1.020 and 1.030 bar and kept constant with a pressure control system. The one compartment cell was degassed for 30 min and it was crosschecked by a GC measurement that no O2 and N2 were detectable. The calibration of the measured counts of produced mol O2 was done by two-electrode configuration with 2 platinum wires in the single compartment cell at different currents (10, 20, 50, 100, 200, 300, 500, 1000, 2000 and 5000 A), followed by a determination of the related mol per count. A three-electrode configuration was used for the GC measurement and the sample was illuminated by a white light LED (Ultra High Power Lightguide Coupled LED, HCRI 5700K from Prizmatix) to reach a similar current as with "one sun" from our solar simulator. Monochromatic light for IPCE measurement was produced using a home-built double monochromator with a halogen light source. The light intensity of the monochromator was calibrated using a Si diode. EIS measurements were performed using an SP-300 Bio-Logic potentiostat with an AC amplitude of 10 mV and a frequency range from 0.2 Hz to 1 MHz. The bias potential steps were approximately 50 mV, with an equilibrium time of 30 s at each step. For the measurement, a white light bias was applied using LEDs (SP-12-W5, cool white Luxeon Rebel). The EIS data were fitted using Zview software.