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.