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

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.