Investigating carrier mobility in hollow and mesoporous ZnSe/ZnTe heterostructures: Microscopic observations of swift charge transfer and visible-light-driven dye decomposition

Abstract

We report herein a one-pot hydrothermal approach to synthesize zinc selenide (ZnSe)/zinc telluride (ZnTe) heterostructures - a set of common cation-based photocatalysts. The crystal structure and phase purity of the heterostructures were verified by powder X-ray diffraction (PXRD) analysis, while field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques were employed to study their morphology, microstructures, and surface electronic states, respectively. Notably, a detailed XPS analysis was conducted to discern the chemical species present on the surface of the photocatalyst, providing valuable insights into the compound's stability in an aqueous medium. Furthermore, the synthesized hybrid structures were utilized to fabricate Schottky barrier diodes, enabling a study of their electrical and dielectric properties using the Spatial-charge-limited conduction (SCLC) mechanism. The key charge transport parameters for all the photocatalysts, namely, carriers' mobility and transit time, influencing the photo response and consequently, dye degradation were estimated. Notably, the ZnSe/ZnTe heterostructure, comprising 50 % ZnSe and 50 % ZnTe, exhibited the highest mobility (3.36 × 10-6 S/m in the dark, increasing to 1.70 × 10-5 S/m in light) and proved to be the most effective photocatalyst for degrading Rhodamine B (with up to ∼ 78 % degradation over 60 min of solar light irradiation) - underscoring the pivotal role of carriers' mobility in governing the photocatalytic activity. Moreover, the ZnSe/ZnTe heterostructure demonstrated a remarkable reduction in the photo-corrosion process, a key challenge affecting the photocatalytic activity of numerous materials. Our discussion highlighted the efficient separation of photoinduced electron-hole pairs in the ZnSe/ZnTe heterostructure, facilitated by the synergistic effects of ZnSe and ZnTe, leading to the achievement of the highest photocatalytic performance.