Revisiting electrode area accuracy in photoelectrochemical measurements

During photoelectrochemical measurements, the exposed area of the photoelectrodes is normally used to calculate the photocurrents. However, it is critical to ascertain what a reliable and accurate electrode area is. In this study, a highly stable TiO 2 nanorod photoanode has been prepared to clarify the effects of the illumination direction, exposed area size, lateral collection, and parasitic absorption. Different from previous explanations, we have found that the edge region of the exposed area can contribute additional carriers, resulting in a higher photocurrent under the back illumination. When the back illumination is used, the parasitic absorption of fluorine-doped tin oxide (FTO) glass can reduce the photocurrents. A large exposed area (e.g., >0.5 cm 2 for the TiO 2 photoanode) should be measured to minimize the determining error. This work will promote standardized measurement protocols and facilitate the steady progression of photoelectrochemistry toward practical applications.