Preparation and Photoelectrochemical Performance of Visible-Light Active Agl/TiO2-NTs Composite with Rich β-Agl

AgI sensitized TiO2 nanotube arrays (AgI/TiO2-NTs) with adjustable beta/gamma ratio of AgI were prepared by a simple dissolution-precipitation-calcination process. The samples were characterized by various techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, linear sweep voltammetry, electrochemical impedance spectroscopy, and Mott-Schottky plots. We found that calcination temperature (100-500 degrees C) had significant effect on regulating the phase of AgI. After calcination at 350 degrees C, the highest beta/gamma ratio of AgI was achieved. Moreover, greatly enhanced photocurrent response and reduced charge transfer resistance were also observed, which together led to easier generation and separation of photogenerated electron-hole pairs. Thus, for the reduction of Cr(VI) under visible light, significantly enhanced photoelectrocatalytic (PEC) performance was observed using AgI/TiO2-NTs calcined at 350 degrees C (denoted as AgI/TiO2-NTs350) as photoanode and Ti foil as cathode, respectively. At very low content of AgI (1.25%), the estimated k(Cr(VI)) (0.0155 min(-1)) was nearly 5 times that of pure TiO2-NTs350.