Controlled solvothermal synthesis of Bi5O7I nanoparticles for enhanced photocatalytic degradation of paracetamol

A bismuth oxyiodide photocatalytic material was synthesized using a simple solvothermal method, followed by calcination at temperatures ranging from 340 °C to 500 °C. The multiform bismuth oxyiodides obtained via in situ phase transformation using BiOI as precursors were evaluated by the catalytic degradation of paracetamol under simulated sunlight irradiation in an aqueous solution. Several characterization tools were employed to study the phase structures, morphologies, and optical properties of the samples. The results showed that BiOI was completely transformed into Bi4O5I2 at 410 °C, which was further decomposed into Bi5O7I when the temperature was raised to 500 °C. These bismuth oxyiodides exhibited a distinct band structure that allowed for the adjustment of oxidation and reduction abilities of the band energy levels. The highest photocatalytic activity was achieved by Bi5O7I, which completely degraded paracetamol after 45 min of irradiation. The improvement in catalytic performance activity was attributed to the high ability of holes to oxidize bismuth-rich Bi5O7I, its specific surface area, and the introduction of I vacancies effectively lowers the recombination of photocarrier and changed the band structure of Bi5O7I. Moreover, the Bi5O7I catalyst showed excellent photostability in a five cycle photocatalytic experiment. This study provides a strategy for the development of highly efficient bismuth oxyhalides for the construction of a high performance photocatalyst material for environmental applications.