Improving photoelectrochemical water oxidation activity of BiFeO3 photoanode via surface passivation

Bismuth iron oxide (BiFeO3) has attracted widespread attention in the field of photoelectrochemistry due to its special ferroelectric properties. However, its high charge recombination from defects and sluggish water oxidation kinetics limit the potential application. Herein, oxygen vacancies are first introduced in BiFeO3 thin films by Ar annealing to improve the bulk charge transfer efficiency. Subsequently, a p-type conductive poly(3, 4-ethylenedioxythiophene) (PEDOT) is employed to suppress the surface-defect-related recombination of photogenerated carriers and to form a p–n junction to increase the charge extraction efficiency. As a result, the photocurrent density of the optimized NiCoFe-Bi/PEDOT/BiFeO3 photoanode reaches 0.17 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE) under simulated 1 sun irradiation for water oxidation, which is enhanced by six times compared with that of the photoanode without PEDOT modification. The photocurrent density is further improved to 0.23 mA cm−2 at 1.23 V vs RHE through polarization of the ferroelectric material. This study strongly suggests that surface passivation is an effective way to improve the activity of the BiFeO3 photoanode for solar water splitting.