Enhanced Energy Storage Properties of Red Phosphorus/Black Phosphorus Hybrid Nanostructures

Abstract

The systematic investigation of the synthesis and characterisation of black phosphorus (BP) and red phosphorus (RP) hybrids was conducted to delve into their structural, morphological, and electrochemical properties. A solvothermal approach facilitated the phase transition from amorphous red phosphorus to crystalline orthorhombic black phosphorus, as evidenced by X-ray diffraction (XRD) and Raman spectroscopy analyses. The XRD analysis demonstrated the emergence of layered BP structures when subjected to temperatures exceeding 160 °C, with a complete phase transition occurring at 200 °C with lattice parameters a = 3.311 Å, b = 10.421 Å, and c = 4.373 Å. The Raman spectra provided additional confirmation of the structural transformation, revealing distinct BP modes at 361.62 cm⁻¹ (A_g^1), 443.22 cm⁻¹ (B_2g), and 468.56 cm⁻¹ (A_g^2).Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) validated the crystalline characteristics of BP, revealing lattice fringes that align with the (111) plane and an interplanar spacing measured at 0.245 nm. The application of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) has elucidated a hierarchical layered morphology for BP, devoid of any detectable impurities. The Brunauer–Emmett–Teller (BET) analysis revealed that the BP/RP hybrid possesses a superior specific surface area of 29.30 m²/g, in contrast to pristine BP at 16.27 m²/g and RP at 3.86 m²/g, thereby improving its electrochemical performance. The electrochemical characterisation conducted for supercapacitor application through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) demonstrated that the BP/RP hybrid displayed exceptional pseudocapacitive behaviour, achieving a specific capacitance of 87 F/g at a current density of 0.5 A/g, which is markedly greater than the capacitance values reported in previous literature.