Insight into the effect of pH on the ferroelectric polarization field applied in photoelectrochemical water oxidation

The polarization field of ferroelectric materials can increase the performance of a photoelectrode by manipulating the band bending at the solid-liquid interface. However, the effect of pH of an electrolyte to the ferroelectric polarization field when applied to photoelectrochemical water oxidation is still not clear. In this work, hematite and tetragonal barium titanate nanoparticles are synthesized to construct a ferroelectric-semiconductor hybrid photoanode. We find that the photocurrent density of the positive polarized photoanode is improved about 30% in the near neutral electrolyte. However, this effect is disappeared in the high pH electrolyte. The ferroelectric polarization field is beneficial to improve the surface states and the donor density in the space charge layer of the photoanode to enhance the hole collection ability and the water oxidation kinetics in a near neutral electrolyte. Through the molecular dynamic simulation, we find that the adsorption capacity of OH − groups on the polarized barium titanate is reduced at high pH value, thus weakens the impact of the ferroelectric polarization field. Our work can maximize the utilization of the ferroelectric materials by selecting the pH value of the electrolyte and provides a new insight into the mechanism of ferroelectrics on photoelectrochemical reactions.