MXene/Bi12O17Cl2/Bi2S3 Ternary Schottky-Type II Heterojunction: Photothermal Boosted Interfacial Charge Transfer for Ultrasensitive Photoelectrochemical Sensing of Tetracycline

Constructing multicomponent heterojunctions to extend carrier lifetime is a common strategy to improve the sensitivity of photoelectrochemical (PEC) sensing. However, sluggish interfacial charge-transfer kinetics still limit the utilization efficiency of photogenerated carriers. Herein, an MXene/Bi12O17Cl2/Bi2S3 (MXene/BOC/BS) ternary heterojunction is successfully constructed via an in situ growth strategy for ultrasensitive PEC sensing of tetracycline (TC). Benefiting from the Schottky junction between MXene and BOC together with the type-II heterojunction between BOC and BS, built-in electric fields are established within the ternary heterojunction, effectively promoting the spatial separation and directional migration of photogenerated charge carriers. Meanwhile, the excellent photothermal conversion capabilities of MXene and BS accelerate interfacial charge-transfer kinetics and facilitate carrier migration during PEC sensing. Under the synergistic effect of prolonged carrier lifetime and photothermal-enhanced charge transfer, photogenerated holes accumulated on the BS surface efficiently oxidize TC molecules, resulting in a significantly enhanced photocurrent response. Consequently, the fabricated PEC sensor achieves ultrasensitive TC detection with a low detection limit down to 4.98 pM, together with excellent selectivity, stability, and satisfactory performance in real-sample analysis. This work provides a new strategy for improving PEC sensing performance through photothermal-accelerated interfacial charge transfer.