A more accurate, reliable method to evaluate the photoelectrochemical performance of semiconductor electrode without under/over estimation

A more accurate and reliable method is proposed to evaluate the photoelectrochemical (PEC) performance of semiconductor toward water splitting. Conventionally, I-t measurements are conducted at a fixed potential relative to the reference electrode, e.g., 0 V vs. Ag/AgCl, to monitor the photocurrent, which has been regarded as a direct indicator for performance comparison among different electrodes. Considering that the open-circuit potential (OCP) varies from electrode to electrode, the photocurrent comparison at a fixed potential may misrepresent the actual differences between samples. Here, we study the PEC performance by applying two distinct external bias values, one at 0 V vs. Ag/AgCl deriving from the conventional practice and the other at 0.1 V vs. OCP representing the exactly fixed applied overpotential. Two experimental groups are designed to address the arguments, including the influence of heat treatment for ZnO nanorod arrays and the global comparison among ZnO, TiO ₂ , Au particle-decorated TiO ₂ , and CdS electrodes. Different trends in photocurrent are observed at the two distinct biases, with the results from 0.1 V vs. OCP conforming to the general considerations. The results suggest that application of a fixed potential relative to the OCP will provide a more fair comparison for accurate PEC performance evaluation without under- or over-estimation.