Photoelectrochemical properties of TiO2 Nanotube Arrays Modified with BiOCl nanosheets

• BiOCl were deposited on TiO2 NTAs by sequential chemical bath deposition.
• BiOCl can decrease background photocurrent and increase current response.
• High sensitivity BiOCl/TiO2 is due to the direct oxidation of organics on BiOCl.

BiOCl nanosheets were deposited on anodized TiO2 nanotube arrays (NTAs) by sequential chemical bath deposition method to get BiOCl/TiO2 NTAs for photoelectrochemical detection of organic compounds (represented by glucose). The structures, elemental components and morphologies of TiO2 and BiOCl/TiO2 NTAs were characterized by using X-ray diffraction diffractometer, scanning electron microscope and transmission electron microscope. The photoelectrochemical behaviors of TiO2 and BiOCl/TiO2 NTAs in the buffer and glucose solutions were measured by cyclic votammetry and amperometry with different optical powers. The modification of BiOCl nanosheets on TiO2 NTAs decreases the photocurrents of TiO2 NTAs in the buffer solution and increases the current response to glucose. Both of the background photocurrent decrease and current response increase are benefit for photoelectrochemical detection of organic compounds. When glucose was used as the target organic compound, the optimized BiOCl/TiO2 NTAs sensor achieved a sensitivity of 0.327 μA/μM (0.417 μA·cm−2·μM−1), linear range from 0 to 1300 μM and calculated detection limit of 5.7 μM. Mechanisms of BiOCl modification were studied by measuring the optical absorption and hydroxyl radical HO· productivity. The transfer of holes from TiO2 to BiOCl and the direct oxidation of organic compounds on BiOCl nanosheets led to the decrease of background photocurrent (lower reaction rate of water splitting on BiOCl nanosheets) and the increase of current response to organic compounds (higher reaction rate of direct oxidation of organic compounds).