Piezoelectric-Effect-Enhanced Full-Spectrum Photoelectrocatalysis in p-n Heterojunction

Photoelectrochemical (PEC) water splitting offers a promising strategy for converting solar energy to chemical fuels. Herein, a piezoelectric-effect-enhanced full-spectrum photoelectrocatalysis with multilayered coaxial titanium dioxide/barium titanate/silver oxide (TiO2/BTO/Ag2O) nanorod array as the photoanode is reported. The vertically grown nanorods ensure good electron conductivity, which enables fast transport of the photogenerated electrons. Significantly, the insertion of a piezoelectric BaTiO3 (BTO) nanolayer at the p-type Ag2O and n-type TiO2 interface created a polar charge-stabilized electrical field. It maintains a sustainable driving force that attract the holes of TiO2 and the electrons of Ag2O, resulting in greatly increased separation and inhibited recombination of the photogenerated carriers. Furthermore, Ag2O as a narrow bandgap semiconductor has a high ultraviolet-visible-near infrared (UV-vis-NIR) photoelectrocatalytic activity. The TiO2/BTO/Ag2O, after poling, successfully achieves a prominent photocurrent density, as high as 1.8 mA cm(-2) at 0.8 V versus Ag/Cl, which is about 2.6 times the TiO2 nanorod photoanode. It is the first time that piezoelectric BaTiO3 is used for tuning the interface of p-type and n-type photoelectrocatalyst. With the enhanced light harvesting, efficient photogenerated electron-hole pairs' separation, and rapid charge transfer at the photoanode, an excellent photoelectrocatalytic activity is realized.