The phenomenon of increasing capacitance induced by 1T/2H-MoS2 surface modification with Pt particles – Influence on composition and energy storage mechanism

Abstract

In this paper, several approaches to the synthesis of molybdenum-based electrode materials for supercapacitors are presented, including anodization, hydrothermal process and annealing. For the material prepared via anodization of a molybdenum plate, followed by a hydrothermal process in thiourea aqueous solution, a thorough study of the Pt-surface modification through repetitive cycling in 1 M sulfuric acid with Pt acting as a counter electrode is performed, including X-ray photoelectron spectroscopy analysis and energy storage mechanism contribution. Along with the increasing number of cycles, an increase of the capacitance value is observed up to 1.064 F cm −2 after 60 000 cycles, resulting in more than tenfold growth (by over 1 150%). The analysis reveals progressive changes in the electrode material's chemical composition and the increasing pseudocapacitance contribution in energy storage processes, which is strictly caused by the formation of mixed molybdenum oxides with oxygen vacancies. Thus, Pt-surface modification effectively improves the electrochemical performance of the electrode material with excellent coulombic efficiency and capacitance retention. In a symmetric two-electrode configuration with Pt-modified electrode materials, the areal capacitance of 140.5 mF cm −2 is obtained after 50 000 cycles (with capacitance retention of 123%) indicating that Pt-surface modification of MoS 2 may provide a novel approach for electrode materials for high-performance supercapacitors.