Phosphorus vacancy regulation and interfacial coupling of biotemplate derived CoP@FeP2 heterostructure to boost pseudocapacitive reaction kinetics

Transition metal phosphide (TMP) is an attractive candidate for asymmetric supercapacitors (ASCs), but their low electric conductivity, limited redox active sites and sluggish charge transfer kinetics are still challenging. Herein, various phosphorus vacancy modified CP/FP heterostructures are successfully acquired via general three-step approach. Benefiting from their natural hierarchical heterostructure, these materials can access more active sites ions for redox reaction and boost their charge transfer kinetics. The formed phosphorus vacancy in lattice structure can provide plentiful lone pair electrons to facilitate electric conductivity. As a result, the pV-CP/FP2 electrode material achieves the best electrochemical performances, which delivers a specific capacitance (1028.8F/g at 5 mV s−1), outstanding rate capability and good cycling performance. Furthermore, the ASCs matched with pV-CP/FP2 and FeOOH electrode yields an exceptional cycling stability (85.7 % retention after 10,000 cycles), good Coulombic efficiency of 73.9 % from 1 to 8 A/g, a high energy density of 45.5 Wh kg−1 at a power density of 700 W kg−1, and as well maintains 36.0 Wh kg−1 at 5600 W kg−1. This work could supply original insights into the defect regulation and interfacial coupling of diatomite derivate heterojunctions for ASCs, and the Coscinodiscus-like pV-CP/FP2 electrode shows great potential for energy storage devices.