Hierarchical MOF-Derived Cu/Cu3P@C Nanocomposites via Sequential Carbonization–Phosphorization for Enhanced Supercapacitor Performance

Abstract Rational design of metal–organic framework (MOF)-derived nanocomposites with abundant active sites and high electrical conductivity is critical for enhancing the supercapacitor performance. In this study, Cu-based MOFs (Cu-BTC) were converted to Cu/Cu3P@C (Cu/C–P) nanocomposites through a sequential carbonization–phosphorization strategy. A hierarchical octahedral carbon skeleton was initially constructed via carbothermal reduction, followed by phosphorization to generate highly active Cu and Cu3P nanoparticles. Density functional theory (DFT) calculations and electrochemical impedance spectroscopy (EIS) results revealed that the optimized Cu/C–P-10 electrode exhibited higher electrical conductivity and minimal charge transfer resistance, demonstrating accelerated charge transfer kinetics. In a three-electrode system, the optimal Cu/C–P-10 electrode achieved a specific capacitance of 745.86 F/g at 0.5 A/g, representing a 1.97-fold enhancement compared with the solely carbonized Cu/C–P-0 electrode and 1.51-fold enhancement compared with the directly phosphated Cu–P-10 electrode. Subsequently, an asymmetric supercapacitor (Cu/C–P-10//AC ASC) was assembled by using the Cu/C–P-10 electrode as the positive electrode and commercial activated carbon (AC) as the negative electrode. This device exhibited good electrochemical performance, delivering an energy density of 41.67 Wh/kg and a power density of 375 W/kg. The exceptional energy storage performance can be attributed to three key factors: (i) enhanced electrical conductivity from metal phosphides, which facilitates charge transfer within the electrodes; (ii) Cu/Cu3P nanoparticles significantly boosting energy storage capacity through pseudocapacitive mechanisms; and (iii) a hierarchical pore structure promoting electrolyte ion diffusion and interfacial contact. This study provides a versatile strategy for the rational design of MOF-derived electrode materials for advanced energy storage applications.