Synthesis of Se-doped ZnO nanoplates with enhanced photoelectrochemical and photocatalytic properties

In this work, we demonstrate a novel and facile two-step strategy for large scale synthesis of Se-doped ZnO nanoplates by combining mechanical alloying with annealing process, in which ZnSe nanocrystals were firstly prepared via a mechanical alloying method, and followed by annealing process in air to incorporate Se as a dopant in ZnO to form Se-doped ZnO nanoplates. X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) studies indicate that the as-fabricated Se-doped ZnO is the wurtzite ZnO structure. X-ray photoelectron spectroscope (XPS) and Raman results reveal that Se is successfully doped into ZnO. UV-vis absorption spectra of the Se-doped ZnO nanoplates reveal the significantly enhanced light absorbance compared with undoped ZnO nanocrystals. Room temperature photoluminescence (PL) spectra indicate that recombination of photogenerated charge carriers for Se-doped ZnO nanoplates is inhibited significantly. The achieved Se-doped ZnO nanoplates show remarkably enhanced photoelectrochemical (PEC) and photocatalytic degradation activity. The photocurrent density of Se-doped ZnO nanoplates reaches up to ∼0.2 mA/cm², which is significantly larger than that of undoped ZnO nanocrystals (∼0.015 mA/cm²). The photodegradation of methylene blue (MB) dye in 2.5 h over Se-doped ZnO nanoplates is about 94.5%, which is significantly enhanced to the undoped ZnO nanocrystals (59.4%). Furthermore, Se-doped ZnO nanoplates show high stability after being used for photocatalytic degradation organic dye during 4 cycles.