Controlled Selenium Infiltration of Cobalt Phosphide Nanostructure Arrays from a Two-Dimensional Cobalt Metal-Organic Framework: A Self-Supported Electrode for Flexible Quasi-Solid-State Asymmetric Supercapacitors

Various hybrid materials containing transitional metals (TMs) with selenium (Se) have been widely studied, but the controlled infiltration of Se in a cobalt phosphide nanostructured array (CPNA) derived from a two-dimensional cobalt metal-organic Framework (2D Co-MOF) is the different approach of material design for energy storage applications. In this work, 2D Co-MOF arrays are successfully grown on an activated carbon fiber textile (ACFT) and converted into Se-x@CPNA-ACFT through successive phosphidization and selenium infiltration processes under the optimized conditions. In the three-electrode system, Se-0.6@CPNA-ACFT shows a higher specific capacity of similar to 302 mAh g(-1) and excellent cycling stability with a capacity retention of similar to 93.8% after 10,000 cycles. The flexible quasi-solid-state asymmetric supercapacitor (ASC) based on Se-0.6@CPNA-ACFT as a positive electrode and FeS2 decorated reduced graphene oxide at etched CFT (FeS2@rGO-ECFT) as a negative electrode exhibits a maximum energy density of similar to 70.6 Wh kg(-1) (volumetric energy density of similar to 1.81 mWh cm(-3)) and a maximum power density of 8.163 kW kg(-1) with remarkable stability. This work provides a good example of the rational modification of a 2D Co-MOF into an efficient Se-0.6@CPNA-ACFT electrode material for a high-performance quasi-solid-state flexible ASC for future energy storage applications.