Microwave-assisted interfacial oxygen-bridge bonding for enhanced performance of MnO2/CNT heterostructures in asymmetric supercapacitors

Abstract

Manganese dioxide, as a typical electrode material for supercapacitors, has been extensively studied. However, its actual capacity, which falls far below the theoretical value, along with sluggish kinetics and unsatisfactory stability, still necessitate the development of convenient and effective improvement strategies. Herein, an interfacial oxygen-bridge chemical bonding constrained MnO₂/carbon nanotube (CNT) heterojunction has been prepared via a microwave-assisted hydrothermal process. The strong interfacial reaction induced by microwave-assistance generates abundant heterointerfaces and interfacial Mn–O–C bonds, which enhance electrical conductivity, accelerate reaction kinetics, and improve structural stability. As a result, the MnO₂/CNT heterojunction exhibits enhanced electrochemical performance in terms of specific capacitance (352.6 F g⁻¹ at 1 A g⁻¹), rate capability (172.6 F g⁻¹ at 20 A g⁻¹) and cyclability (93.6% of initial capacitance retained after 5000 cycles at 10 A g⁻¹). Moreover, the assembled MnO₂/CNT//AC shows a high energy density of 29.5 W h kg⁻¹ at a power density of 900 W kg⁻¹ and outstanding cycling stability with 91.2% capacitance retention after 5000 cycles at 3 A g⁻¹. This work highlights the potential of microwave-assisted interface engineering to enhance the performance of MnO₂-based electrode materials for practical applications.