Hydrothermal engineering of polyethylene glycol-assisted boron nitride/hematite nanohybrid composites for high-performance supercapacitors

Abstract

Developing high-performance energy storage materials is essential to meet the increasing global demand for sustainable energy solutions. In this study, a novel strategy is employed to synthesize polyethylene glycol-assisted boron nitride/hematite (PEG-BN/α-Fe₂O₃) hybrid composites through a hydrothermal process. Polyethylene glycol(PEG) serves as both a dispersant and a non-covalent linker that bridges hematite nanoparticles and BN sheets. With a combination of van der Waals interaction and hydrogen bonding with the component materials, PEG enables stable and homogeneous dispersion of hematite on the otherwise inert and agglomeration-prone BN surface. This dual interaction approach enables controlled interface engineering, solving one of the major challenges commonly faced in the synthesis of BN-based composites. It also acts as a functional modifier that modulates the interfacial interactions and regulates the nucleation and dispersion of α-Fe₂O₃ nanoparticles within the BN matrix. The incorporation of PEG enhanced the electrochemical and structural properties of the hybrid composite. Structural and morphological characterizations confirmed the uniform dispersion of α-Fe₂O₃ within the BN matrix, with PEG enhancing the interfacial interactions and overall material stability. TGA demonstrated that PEG incorporation significantly improved the thermal stability of the composites, delaying degradation and preserving structural integrity under high-temperature conditions. Electrochemical measurements, including CV and GCD analysis in a 6 M KOH electrolyte, revealed superior charge storage capabilities for PEG-BN/α-Fe₂O₃ compared to BN/α-Fe₂O₃. This hybrid composite exhibited a remarkable specific capacitance of 361.6 F g⁻¹ at a current density of 3 A g⁻¹, significantly outperforming the individual components. The GCD studies display an enhanced charge retention capability of the hybrid composite with a coulombic efficiency of 83%, indicating reduced internal resistance and improved kinetics. Additionally, electrochemical impedance spectroscopy indicated a lower charge transfer resistance and enhanced conductivity in PEG-modified composites. The composite also retained 85% of its initial capacitance after 5000 cycles, demonstrating excellent cyclic stability. The improved electrochemical performance of PEG-BN/α-Fe₂O₃ hybrid composites is attributed to the synergistic effects of BN and α-Fe₂O₃, facilitated by PEG, which acts as a thermal buffer, prevents agglomeration, and enhances electrolyte–electrode interactions. These findings underscore the potential of PEG-assisted BN/α-Fe₂O₃ composites as advanced electrode materials for next-generation supercapacitors and other electrochemical storage devices.