Preparation of Rod-shaped Bi5O7I as Bifunctional Material for Supercapacitors and Photcatalysts

The preparation of new functional materials is one of the most effective, yet difficult methods for solving both energy shortage and environmental pollution problems. Bismuth iodide series oxides have been increasingly studied and favored in the field of supercapacitors and photocatalysts due to their unique morphological characteristics and excellent electrochemical performance. In this study, 3D rod-shaped Bi5O7I rich in bismuth and oxygen was synthesized from BiOI by adjusting the pH. A variety of advanced characterization techniques were used to systematically study the chemical composition, structural characteristics, surface properties, morphological characteristics and electrochemical and photocatalytic performance. Results showed that flaky BiOI and 3D rod-shaped Bi5O7I were successfully prepared with good crystal structure and high phase purity. The electrochemical impedance spectroscopy (EIS) of rod-shaped Bi5O7I were lower than BiOI because Bi3+ could easily migrate in Bi5O7I to reach a higher specific capacitance value (363 F/g). The high capacitance retention rate (72.9%) of rod-shaped Bi5O7I electrode indicated its high-rate capability. In addition, because of the large forbidden band width and suitable conduction and valence band positions of Bi5O7I, an increased number of holes could be generated under visible light radiation while the recombination of electrons and holes could be effectively hindered, thereby improving the photocatalytic performance. Carbamazepine (CBZ) anticonvulsant wastewater was degraded efficiently with a degradation rate of 97.1%, and K (degradation rate constant) of 0.021/min. In addition, recycling performance was also satisfactory, and the degradation efficiency of CBZ still remained above 85% after 6 cycles. This study provides a new way to develop new efficient supercapacitor electrodes for degrading organic pollutants in the environment.