Phosphorization Engineering on a MOF-Derived Metal Phosphide Heterostructure (Cu/Cu3P@NC) as an Electrode for Enhanced Supercapacitor Performance

Abstract

A highly conductive and rationally constructed metal-organic framework (MOF)-derived metal phosphide with a carbonaceous nanostructure is a meticulous architecture toward the development of electrode materials for energy storage devices. Herein, we report a facile strategy to design and construct a new three-dimensional (3D) Cu-MOF via a solvent diffusion method at ambient temperature, which was authenticated by a single-crystal X-ray diffraction study, revealing a novel topology of (2,4,7)-connected three-nodal net named smm4. Nevertheless, the poor conductivity of pristine MOFs is a major bottleneck hindering their capacitance. To overcome this, we demonstrated an MOF-derived Cu₃P/Cu@NC heterostructure via low-temperature phosphorization of Cu-MOF. The electronic and ionic diffusion kinetics in Cu₃P/Cu@NC were improved due to the synergistic effects of the heterostructure. The as-prepared Cu₃P/Cu@NC heterostructure electrode delivers a specific capacity of 540 C g^-1 at 1 A g^-1 with outstanding rate performance (190 C g^-1 at 20 A g^-1) and cycle stability (91% capacity retention after 10,000 cycles). Moreover, the assembled asymmetric solid-state supercapacitor (ASC) achieved a high energy density/power density of 45.5 Wh kg^-1/7.98 kW kg^-1 with a wide operating voltage (1.6 V). Long-term stable capacity retention (87.2%) was accomplished after 5000 cycles. These robust electrochemical performances suggest that the Cu₃P/Cu@NC heterostructure is a suitable electrode material for supercapacitor applications.