Band gap engineering design for construction of energy-levels well-matched semiconductor heterojunction with enhanced visible-light-driven photocatalytic activity

Abstract

Energy-levels well-matched Mg_1−xCu_xWO₄ (0.1 < x < 0.5)/Bi₂WO₆ heterojunctions with Type II staggered conduction bands and valence bands have been successfully constructed by band gap engineering based on solid-solution design and synthesized by a facile one-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS) were utilized to characterize the crystal structures, morphologies and optical properties of the as-prepared products. The as-designed Mg_0.7Cu_0.3WO₄/Bi₂WO₆ heterojunctions consisting of nanocube and nanoplate structures exhibit much higher visible-light-driven (VLD) photocatalytic activity than the two individual components for the degradation of RhB and photocurrent generation. The photoluminescence (PL) spectra, photoelectrochemical measurement, active-species trapping and quantification experiments all indicated that the fabrication of energy-levels well-matched overlapping band structures can greatly facilitate the separation and easy transfer of photogenerated electrons and holes, thus resulting in remarkably enhanced photocatalytic activity. This work provides a novel strategy for semiconductor heterojunction construction and energy band structure regulation.