Interface engineering of a hollow core-shell sulfur-doped Co2P@Ni2P heterojunction for efficient charge storage of hybrid supercapacitors

Transition metal phosphides (TMPs) are widely used as supercapacitor energy storage materials due to their abundant valence and high theoretical capacity, but their poor electrical conductivity and low active ma-terial utilization lead to low actual capacity and slow kinetics. Herein, we demonstrate the excellent electrochemical properties of sulfur-doped Co2P@Ni2P heterojunction materials prepared using a combi-nation of hydrothermal, ion-exchange and low-temperature annealing approaches. For sulfur-doped Co2P@ Ni2P, hollow core-shell microstructures increase the number of electroactive sites and provides a shortcut for electron transport, while sulfur doping promotes the transfer and rearrangement of interfacial charge from Co2P to Ni2P, optimizing the redox ability of the active component. In addition, the S doping and the highly electrochemically active nickel-cobalt phosphide synergistically accelerate the charge transfer, which leads to fast reaction kinetics. Therefore, the obtained S-Co2P@Ni2P exhibits an optimal specific capacity of 1200 C g-1 at 1 A g-1 and excellent rate performance. Furthermore, when combined with activated carbon (AC) for hybrid supercapacitor (HSC), the S-Co2P@Ni2P//AC device shows an excellent energy density of 41.5 Wh kg-1 and a high-capacity retention of 93 % after 15,000 cycles. This work provides a novel approach for the exploration of high-performance and stable phosphorus-based battery-like supercapacitor mate-rials.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrates the excellent electrochemical properties of sulfur-doped Co2P@Ni2P heterojunction materials. The hollow core-shell microstructures of sulfur-doped Co2P@Ni2P increase the number of electroactive sites and provide a shortcut for electron transport. Sulfur doping promotes the transfer and rearrangement of interfacial charge, optimizing the redox ability of the active component. Additionally, the sulfur doping and the highly electrochemically active nickel-cobalt phosphide synergistically accelerate the charge transfer, resulting in fast reaction kinetics. The obtained S-Co2P@Ni2P exhibits an optimal specific capacity of 1200 C g-1 at 1 A g-1 and excellent rate performance. Furthermore, when combined with activated carbon (AC) for hybrid supercapacitor (HSC), the S-Co2P@Ni2P//AC device shows an excellent energy density of 41.5 Wh kg-1 and a high-capacity retention of 93% after 15,000 cycles.