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A novel nitrogen removal strategy, the combined photoelectrocatalytic oxidation and autotrophic biofilm denitrification, was developed to achieve simultaneous NH 4

AgI sensitized TiO2 nanotube arrays (AgI/TiO2-NTs) with adjustable β/γ 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 °C) had significant effect on regulating the phase of AgI. After calcination at 350 °C, the highest β/γ 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 °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.