Piezoelectric-effect-enhanced photocatalytic performance in Cr/Nb modified Bi4Ti3O12/g-C3N4 Z-scheme system

Abstract

Polarizations within ferroelectric or pizeoelectric materials are conducive to improve photocatalytic activity by promoting interior photogenerated carriers separation. However, the photocatalytic activity of pristine ferroelectric or pizeoelectric semiconductor is generally limited by its insufficient polarization and spectral absorption. Herein, Bi4Ti3-2nCrnNbnO12/x-g-C3N4 (BTCNO-n/x-CN) heterojunctions was prepared by loading ultrathin g-C3N4 on ferroelectric BTCNO synthesized by co-doping Cr3+-Nb5+ pairs into Bi4Ti3O12 (BTO). The Cr3+-Nb5+ pairs co-doping not only endows the heterojunctions stronger pizeoelectric performance but also further promotes the spectral absorption, which were confirmed through the hysteresis loop, piezoelectric potential, density functional theory calculations and UV–vis diffuse reflectance spectra (DRS). The piezo-photocatalytic performance of BTCNO-n/x-CN was investigated in detail by RhB degradation and H2 evolution under light and ultrasound. According to these results, the optimal loading content of g-C3N4 and doping concentration of Cr3+-Nb5+ pairs were determined as n = 0.1 and x = 5 %, and BTCNO-0.1/5%-CN showed an optimal photocatalytic activity for 98.7 % RhB removal ratio after 45 min, and 696 µmol·g−1·h−1 of H2 production rates. The possible Z-scheme charge transfer mechanism in BTCNO-n/x-CN heterojunction was proposed based on the results of capture experiments, which improves photocatalytic performance through enhancing the separation of photogenerated carriers and promotes the generation of O2− and OH. This work utilizes the piezoelectric effect and heterojunctions to enhance interior and surface carriers separation to improve the catalytic activity, which offers a new scheme to design excellent photocatalysts.