Construction of heterojunction photoelectrode via atomic layer deposition of Fe2O3 on Bi2WO6 for highly efficient photoelectrochemical sensing and degradation of tetracycline

The present paper describes the fabrication of a heterojunction photoelectrode by combining the wet chemical synthesis of Bi2WO6 with the formation of Fe2O3 layer by atomic layer deposition (ALD) technique. Fe2O3 with different atomic thicknesses was layered onto spin-coated Bi2WO6 nanoflakes by controlling the number of deposition cycles. The influence of the thickness of the Fe2O3 layers on photoelectrocatalytic detection and remediation was also studied. The deposition of a 15-nm layer of Fe2O3 on Bi2WO6 led to the best photoelectrochemical response under visible light activation. The performance of 15-nm Fe2O3–Bi2WO6 (4.3 μA/cm2) was 3.6 times higher than that of pristine Bi2WO6 (1.2 μA/cm2) at an external bias of 0.6 V. The enhanced performance was due to the increased spectral breadth of light absorption and efficient transfer of photogenerated charge carriers by the suppression of electron–hole pairs. The optimized photoelectrode detected tetracycline antibiotic in aqueous solution with a 0.3 μM limit of detection and photoelectrocatalytically degraded around 95% tetracycline. The heterojunction photoelectrode structure prepared using ALD enables inexpensive, non-enzymatic, amperometric determination and degradation of tetracycline in a stable and reproducible manner via a deduced mechanism. Our strategy can be used to fabricate photoelectrodes for a wide range of applications.