MOF-derived rose-like carbon-coated Ni-Co phosphide with phosphorus vacancies to enhance hydroxide-ion storage in hybrid supercapacitors

The low structural stability and sluggish charge-transfer kinetics of transition metal phosphides (TMPs) hinder their application in hybrid supercapacitors. The realization of advanced OH⁻ storage critically depends on the delicate TMP designs, particularly their chemical composition and structure. Herein, a synergistic engineering approach based on metal–organic framework (MOF)–derived C-coated bimetallic phosphides and P vacancies (Pv) was proposed. Using a Ni-Co based MOF, a one-step high-temperature carbonization and phosphidation method was employed as the precursor to prepare a rose-like Ni_1−xCo_xP composite (Ni_1−xCoₓP@NC), comprising a N-doped C (NC) coating and Pv. Physical characterization and theoretical calculations indicated that the open structure with porous Ni_1-xCo_xP@NC nanosheets originated from high-temperature pyrolysis of Ni-Co based MOF provides abundant redox-active sites, and the NC layer offers excellent mechanical support for persistent electron/OH⁻ transfer. The bimetallic phosphides, surface Pv, and NC coating synergistically enhance the electrical conductivity of TMPs, reduce the energy barriers for OH⁻ adsorption, and accelerate charge-transfer kinetics. The prepared Ni_1−xCo_xP @NC electrode possessing an open architecture exhibits a high specific capacitance (2108 F g⁻¹ at 1 A g⁻¹) and excellent rate capability (1710 F g⁻¹ at 10 A g⁻¹). Furthermore, the assembled active carbon (AC)// Ni_1−xCo_xP P@NC hybrid supercapacitor demonstrates an energy density of 37.7 Wh kg⁻¹ at a power density of 750 W kg⁻¹. Our study presents a promising strategy for modifying TMP electrodes to realize efficient and stable OH⁻ storage in hybrid supercapacitors.