One-step synthesis of MnS/MoS2/C through the calcination and sulfurization of a bi-metal–organic framework for a high-performance supercapacitor and its photocurrent investigation

Abstract

Based on a Mn/Mo-metal organic framework (MOF) precursor, [Mn(4,4′-bipyridine)_0.5 MoO₄]·1.5H₂O, a MnS/MoS₂/C hybrid was synthesized through a calcination and sulfurization approach and it is mainly constituted by MoS₂/C nanorods and MnS/MoS₂/C nanoflakes. The MnS/MoS₂/C hybrid delivers a high specific capacitance of 1162 F g⁻¹ at 0.5 A g⁻¹ in 2 M KOH electrolyte, and it possesses a good rate capacity with a retention of 75.7% (880 F g⁻¹) at 10 A g⁻¹, which is due to the synergetic effects of the components MnS, MoS₂ and carbon matrix in the hybrid material. The carbon matrix in the hybrid material can not only anchor the active components of MnS and MoS₂, but also transport electrons efficiently. The completely exposed Mo and S edges on the preferential 2H-(002) and 3R-(003) facets of MoS₂ are beneficial for ion adsorption and electrochemical reaction. An asymmetric supercapacitor constructed by the MnS/MoS₂/C hybrid (positive electrode) and activated carbon (AC) (negative electrode) exhibited a capacitance retention of 81% after 5000 galvanostatic charge–discharge cycles (GCD). During the GCD process, the metal sulfides were probably transformed into metal hydroxides in the presence of OH⁻ electrolyte ions. In addition, the MnS/MoS₂/C hybrid exhibits a visible light-driven photocurrent response, and DFT calculation proves that it is attributed to the semiconducting feature of MoS₂ in the hybrid.