Preparation of a p-n heterojunction 2D BiOI nanosheet/1DBiPO4 nanorod composite electrode for enhanced visible light photoelectrocatalysis

ABSTRACT In this study, a 2D BiOI nanosheet/1D BiPO 4 nanorod/fluorine-doped tin oxide (FTO) composite electrode with a p-n heterojunction structure was prepared by a two-step electrodeposition method. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible diffuse reflectance spectroscopy, and electrochemical testing were used to characterize its composition, crystal morphology, and optical properties. The BiOI/BiPO 4 /FTO composite electrode has higher photoelectrocatalytic (PEC) activity for the degradation of tetracycline than pure BiPO 4 and BiOI. The PEC activity of the composite was 1.98 times and 2.46 times higher than those of the BiOI/FTO and BiPO 4 /FTO electrodes, respectively. The effects of the working voltage and BiOI deposition time on the degradation of tetracycline were investigated. The optimum BiOI deposition time was found to be 150 s and the optimum working voltage is 1.2 V. Trapping experiments showed that hydroxyl radicals (•OH) and superoxide radicals (•O 2 − ) are the major reactive species in the PEC degradation process. The BiOI/BiPO 4 /FTO composite electrode has good stability, and the tetracycline removal efficiency remains substantially unchanged after four cycles in a static system. The reason for the PEC efficiency enhancement in the BiOI/BiPO 4 /FTO composite electrode is the increased visible light absorption range and the p-n heterojunction structure, which promotes the separation and migration of the photogenerated electrons and holes.