Exploring the microscopic mechanism of pseudocapacitance with electronic structures in monolayer 1T-MoS2 electrodes for supercapacitors

Abstract

Quasi-two-dimensional 1T-MoS₂ is a promising pseudocapacitance (C_redox) electrode material due to its large specific surface area, superior electrical conductivity and mechanical stability. However, the microscopic mechanism of C_redox and its further manipulation via modulating the structures and electronic structures are still unclear. Thus, the C_redox of monolayer 1T-MoS₂ has been explored based on first-principles calculations. For monolayer 1T-MoS₂ adsorbed by H⁺ ions on one side or both sides, a band gap opens, decreases and even disappears with the coverage increase in H⁺ ions up to 100%. In this process, the charge transfer from the monolayer 1T-MoS₂ to the adsorbed H⁺ ions almost linearly increases with the coverage increase in the H⁺ ions. In contrast, the potential change rate of the monolayer 1T-MoS₂ reduces, resulting in the enhancement of C_redox. Herein, the maximum values of C_redox reached ∼76.7 μF cm⁻² (252.8 F g⁻¹) and ∼213.7 μF cm⁻² (704.5 F g⁻¹) for the 100% coverage of H⁺ ions on one side and both sides, respectively. Furthermore, the manipulation of C_redox in the monolayer 1T-MoS₂ could be realized through intrinsic defects engineering. Particularly, the C_redox was greatly improved in the system with S vacancies. These results would provide significantly fundamental insights for understanding the correlation between the C_redox and the electronic structures of 1T-MoS₂ and other similar quasi-two dimensional materials.