Tuning spontaneous polarization to alter water oxidation/reduction activities of LiNbO3

Abstract

Here, we investigated the effects of spontaneous polarization on photoreactivities by using a ferroelectric material n-type congruent LiNbO3 single crystal as a model. It was found that c+ LiNbO3 was superior to c− LiNbO3 in photocatalytic water reduction, while c− LiNbO3 exhibited better performances for photoelectrochemical water oxidation than c+ LiNbO3. Using Kelvin probe force microscopy and open circuit potential methods, we observed that c− LiNbO3 generated a higher photovoltage and had a slower charge-recombination rate than c+ LiNbO3. The results of electrochemical impedance spectroscopy measurements indicated that c− LiNbO3 may favor the hole transport from the bulk to the surface compared with c+ LiNbO3, leading to the anisotropic performances of c+ and c− LiNbO3 in water oxidation/reduction. Therefore, tuning the direction of the polarization may be a strategy to dramatically prompt the photoreactivities of water oxidation or reduction.