Vanadium doping and phosphorus vacancy co-regulation of biotemplate derived three-dimensional cobalt phosphide to enhance pseudocapacitance performance

Abstract

Poor rate performance and low cycling stability are both considered as two major disadvantages when choosing cobalt phosphide as the electrode material of supercapacitor. Herein, we developed an effective strategy to ameliorate above disadvantages by introducing of phosphorus vacancies and doping of vanadium simultaneously (the products labelled as V-CoPx-1). Besides, diatomite was selected as a template to synthesize cobalt phosphide with a diatomite morphology by a mild etching method using KOH aqueous alcohol solution as etching agent. The average oxidation state of Co ions in V-CoPx-1 decreases after the P vacancies are introduced, which can improve the electrical conductivity and provide more active sites for electrochemical reactions. Meanwhile, after the introduction of P vacancies and V heteroatoms, more point defects and unpaired electrons are generated, thus improving the ionic conductivity of the material. The diatomite morphology of V-CoPx-1 and the morphological transformation after the reduction by NaBH4 make the materials have larger specific surface area and higher porosity. The as-synthesized V-CoPx-1 possesses a superior 829 F g−1 at 1 A g−1 and improved cycling life maintaining 80.84% of its original value after 10,000 cycles. Moreover, a fabricated device with V-CoPx-1 (anode) and commercial active carbon (cathode) exhibits 43.3 Wh kg−1 at 800 W kg−1. This supercapacitor also delivers a superior rate performance maintaining 60% retention of specific capacitance from 1 A g−1 to 20 A g−1. This work provides an efficient strategy of defects regulation to boost the electrochemical performance, which hoped to offer insights for the improvement of cobalt phosphide.