Synergistic electrochemical performance of Mn–Li–S MOF integrated with PANI/rGO for supercapattery and hydrogen production applications

Abstract

The incorporation of the hydrogen evolution reaction (HER) in energy storage devices can lead to on-demand hydrogen generation alongside energy storage in the form of hydrogen, leading to a dual-functional platform that couples renewable energy storage with sustainable fuel production. In this pursuit, the present research reports the engineering of a hydrothermally synthesized manganese lithium sulfide-based metal-organic framework (MnLiS-MOF) hybrid electrode material, integrated with polyaniline (PANI) and reduced graphene oxide (rGO), for energy storage and HER applications. SEM, EDX, XRD, and XPS analysis confirmed the successful synthesis of the hybrid nanocomposite material, demonstrating the presence of all elemental constituents and an average crystallite size of 86 nm for MnLiS-MOF/PANI/rGO. The MnLiS-MOF/PANI/rGO electrode presented the highest specific capacity (Qs) of 1125.5 C/g for the three-electrode measurement scheme. The MnLiS-MOF/PANI/rGO//AC asymmetric configuration system, with activated carbon (AC) as the second electrode, presented the highest energy density (E_d) and power density (P_d) of 48 Wh/kg and 1600 W/kg, respectively. Furthermore, it offers 92 % of stable coulombic efficiency and 90 % of capacity retention stability over 8000 repeated charging and discharging cycles. The MnLiS-MOF/PANI/rGO composite's electrode was found to deliver an ultra-low Tafel slope of 35 mV dec⁻¹ for the electrocatalytic HER process. The MnLiS-MOF/PANI/rGO exhibits an overpotential of 35 mV, with a Turnover Frequency (TOF) of 112 s⁻¹. This excellent performance highlights the material's dual functionality, offering a versatile platform for the integrated design of high-efficiency energy storage and hydrogen generation systems.