Direct construction of cobalt selenate-cobalt phosphide composite with exalted energy storage for hybrid supercapacitor cells

Abstract

Recently, metal selenides/phosphides have attracted increasing interest as electrode candidates for energy storage devices due to their high conductivity, redox activity, and specific capacity. Herein, we report the cobalt selenate-cobalt phosphide (CoSeO3-CoP3) composite materials by a two-step synthesis method. Initially, the CoSeO3 was rapidly synthesized via a facile single-step hydrothermal method for 30 min (CSO-30). Benefitting from rich redox-activity and morphological advantages, the CSO-30 electrode exhibited a higher areal capacity (CA) of 351 µAh cm−2 (specific capacity (CS) of 159.5 mAh g−1) at 2 mA cm−2 than those of the CSO electrodes obtained for 15 and 45 min. In the next step, the phosphorization process was performed to modify/alter the CSO-30 crystal structure by incorporating the phosphorus element, which leads to the formation of CoSeO3-CoP3 (CSO-CP) composite. The resultant CSO-CP electrode delivered an improved CA of 627.7 µAh cm−2 (CS of 179.3 mAh g−1) at 2 mA cm−2 compared to the CSO-30 electrode. Furthermore, a hybrid supercapacitor (HSC) cell was fabricated with CSO-CP and activated carbon electrodes. The HSC revealed a maximum energy density of 0.43 mWh cm−2 and a maximum power density of 18.1 mW cm−2. Moreover, the feasibility of the HSC was verified by powering various electronic devices.