General solution-processed formation of porous transition-metal oxides on exfoliated molybdenum disulfides for high-performance asymmetric supercapacitors

Abstract

The combination of hierarchical porous transition-metal oxides with ultrathin two-dimensional (2D) transition-metal dichalcogenides (TMDs) with a favorable electrochemical performance beyond single-component materials is still very challenging. The present work demonstrates the general and targeted synthesis of hybrid heterostructures by the integration of porous transition-metal oxides (TMOs, e.g. NiO, Co₃O₄ and Fe₂O₃) and 2D MoS₂ nanosheets. The as-prepared vertically aligned MoS₂–NiO hybrids exhibit an excellent pseudocapacitive performance, such as a high specific capacitance of 1080.6 at 1 A g⁻¹ and long cycling durability with 101.9% capacitance retention after 9000 cycles at 2 A g⁻¹. This facile strategy using low-cost precursors is regarded as a general method to hybridize 2D MoS₂ with other porous TMOs, such as Co₃O₄ and Fe₂O₃, with largely improved pseudocapacitive performances due to a favorable synergistic effect between MoS₂ and TMOs with an enhanced electronic/ionic transport. Asymmetric supercapacitors using MoS₂–TMO hybrids as both positive and negative electrodes are also demonstrated. As a proof-of-concept, the as-assembled MoS₂–NiO//MoS₂–Fe₂O₃ asymmetric supercapacitor operating within the potential window of 0–1.8 V delivers a high energy density of 39.6 W h kg⁻¹ with a long cycle life and excellent rate capability.