Insight into the influence of high temperature annealing on the onset potential of Ti-doped hematite photoanodes for solar water splitting

For Ti-doped hematite photoanodes, high temperature annealing drastically increases the water oxidation plateau photocurrent, but also induces an anodic shift of onset potential by about 100mV, thus hindering the performance under low applied bias. To the best of our knowledge, the effects of high temperature annealing on the onset potential have been rarely studied. Herein, both X-ray photoelectron spectroscopy (XPS) measurements and theoretical calculations indicated that the increase of surface Ti/Fe atomic ratio after high temperature annealing decreased the adsorption capacity of hydroxide ions on the hematite surface. Subsequently, the flatband potential (i.e., the theoretical onset potential) of Ti doped hematite photoanodes positively shifted, which was supported by the Mott-Schottky measurements.