Synergistic Enhancement of PEC Activity in Heterojunction Assisted by Oxygen Vacancies and Ferroelectric Polarization at Zero Bias: Mechanism Study and Achievement of Ultrasensitive Detection

The utilization of ferroelectric polarization-assisted photoelectrochemical (PEC) systems holds huge promise for solving the issue of high recombination of photogenerated electron–hole pairs. Monitoring their intricate charge-transfer process can offer profound insights into the advancement of highly active photoelectrodes. In this work, the hydrothermally synthesized titanium dioxide nanorod arrays (TiO2 NRAs) are subjected to in situ etching to introduce oxygen vacancies (Ov), and subsequently loaded with barium titanate (BaTiO3, BTO) nanoparticles to form a ferroelectric polarization effect-assisted type-II heterojunction. The resulting Ov-TiO2/BTO demonstrates an ultrahigh photocurrent of 102 μA and outstanding stability over 7200 s, far surpassing majority of recently reported PEC photoanodes operating at a bias voltage of 0 V (vs Ag/AgCl). Notably, the photoinduced charge transfer in ferroelectric Ov-TiO2/BTO was monitored at the microscale by advanced scanning photoelectrochemical microscopy (SPECM). As a showcase, the aptamer-coupled self-powered PEC biosensor for kanamycin presents excellent sensitivity and good anti-interference ability. This study not only elucidates the intrinsic mechanism of the synergistic amplification of photoelectric signals by oxygen vacancies and ferroelectric heterojunctions but also provides a reliable platform for the ultrasensitive detection of biological molecules.