Acid-treated Ti4+ doped hematite photoanode for efficient solar water oxidation—Insight into surface states and charge separation

Acid-treatment has been proved to be an efficient approach to improve the photoelectrochemical (PEC) performance of hematite . However, efforts to optimize hematite photoanode have been limited by an inadequate understanding of the semiconductor surface . Here we make efforts to understand the microscopic charge separation processes of Ti 4+ doped Fe 2 O 3 photoanode before and after acid-treatment. Surface photovoltage (SPV) transient and the work function measurements directly reveal that acid-treatment leads to passivation of the surface states . Surface photovoltage (SPV) spectroscopic studies coupled to open-circuit photovoltage (OPV) measurements indicate that the surface states of hematite photoanode before acid-treatment result in the pinning of the Fermi level , which reduce the intensity of interfacial electric field at the semiconductor-electrolyte interface.