Fig. 3
a J-V curves of the hematite photoanodes with different doping levels in the dark (dashed line) and under one-sun irradiation (solid curves). b Photoelectrochemical impedance spectra measured at 1.23 VRHE. c Mott-Schottky plots. d The change of open circuit potential under the light-on/light-off circle. e Schematic diagram of the equilibrium state of energy band bending in the dark