Engineering Interfacial Built-in Electric Field in Polymetallic Phosphide Heterostructures for Superior Supercapacitors and Electrocatalytic Hydrogen Evolution

Herein, a patterned rod-like CoP@NiCoP core-shell heterostructure is designed to consist of CoP nanowires cross-linked with NiCoP nanosheets in tight strings. The interfacial interaction within the heterojunction between the two components generates a built-in electric field that adjusts the interfacial charge state and create more active sites, accelerating the charge transfer and improving supercapacitor and electrocatalytic performance. The unique core-shell structure suppresses the volume expansion during charging and discharging, achieving excellent stability. As a result, CoP@NiCoP exhibits a high specific capacitance of 2.9 F cm(-2) at a current density of 3 mA cm(-2) and a high ion diffusion rate (D-ion is 2.95 x 10(-14) cm(2) s(-1)) during charging/discharging. The assembled asymmetric supercapacitor CoP@NiCoP//AC exhibits a high energy density of 42.2 Wh kg(-1) at a power density of 126.5 W kg(-1) and excellent stability with a capacitance retention rate of 83.8% after 10 000 cycles. Furthermore, the modulated effect induced by the interfacial interaction also endows the self-supported electrode with excellent electrocatalytic HER performance with an overpotential of 71 mV at 10 mA cm(-2). This research may provide a new perspective on the generation of built-in electric field through the rational design of heterogeneous structures for improving the electrochemical and electrocatalytical performance.