Two-step hydrothermal synthesis of hydrangea-like Bi2O2Se with high performance for supercapacitors

The hydrangea-like structure of Bi2O2Se, 2 O 2 Se, composed of ultra-thin nanosheets, was prepared by a 2-step hydro- thermal method for supercapacitor applications. The unique hydrangea-like structure of Bi2O2Se, 2 O 2 Se, characterized by a substantial specific surface area and abundant pore morphologies, facilitated the infiltration of electrolyte. The presence of bismuth vacancies not only enhanced the conductivity, but also increased the spacing between [Bi2O2]n2n+ 2 O 2 ]n 2n+ and [Se]n2n- 2n- layers, creating room for K+ + insertion/extraction and augmenting the surface- controlled pseudo-capacitance. Consequently, the hydrangea-like Bi2O2Se 2 O 2 Se exhibited a high specific capacitance of 650 F/g at 1 A/g, excellent rate capability of 62 % from 1-20 A/g, and retained 80 % of its initial capacitance after 2000 cycles.