Two Dimensional Oxygen-deficient Bismuth oxy-iodide Nanosheets with Enhanced Supercapacitor Performances
Huichao Wang, Zhengde Wang, Huadong Tian, Rongrong Cheng, Mohan Lin, Xueqin Sun, Songlin Ran, Yaohui Lv
Abstract
Introducing oxygen vacancy into oxides has become an effective strategy for enhancing the electrochemical performance. Herein, a series of identical two-dimensional BiOI nanosheets with various concentration of oxygen vacancies are rationally fabricated through a facile ion-exchange and annealing process under Ar atmosphere. The presence of oxygen vacancies has been identified by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to probe the evolution of crystal structure and morphology of the product. Electrochemical data show that reduced two-dimensional BiOI nanosheets electrodes with appropriate oxygen vacancies exhibit a significant improvement on capacitance compared to the pristine electrodes. The specific capacitance of the as-prepared BiOI-600 electrode reaches 620 F g -1 (at 0.5 A g -1 ), and 65 % capacitance retention after 1000 cycles at 2 A g -1 . The good electrochemical performances can be mainly ascribed to the convenient diffusion of electrolyte ions ( e.g. two dimensional nanosheets) and more surface active sites ( e.g. oxygen vacancies) for redox reactions. These findings provide new chance for the oxygen-vacancies-rich two-dimensional BiOI nanosheets as high-performance supercapacitor electrodes.