Piezoelectric‐Effect‐Enhanced Full‐Spectrum Photoelectrocatalysis in p–n Heterojunction

Abstract 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 (TiO 2 /BTO/Ag 2 O) 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 BaTiO 3 (BTO) nanolayer at the p‐type Ag 2 O and n‐type TiO 2 interface created a polar charge‐stabilized electrical field. It maintains a sustainable driving force that attract the holes of TiO 2 and the electrons of Ag 2 O, resulting in greatly increased separation and inhibited recombination of the photogenerated carriers. Furthermore, Ag 2 O as a narrow bandgap semiconductor has a high ultraviolet–visible–near infrared (UV–vis–NIR) photoelectrocatalytic activity. The TiO 2 /BTO/Ag 2 O, 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 TiO 2 nanorod photoanode. It is the first time that piezoelectric BaTiO 3 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.