<i>In situ</i> growth of layered 1T-MoS₂ onto carbon nanofibers as a strategy towards advanced hybrid materials for electrochemical energy storage and catalysis

Supercapacitors for electrochemical energy storage and electrocatalysts for hydrogen evolution reaction (HER) are pivotal in addressing global energy challenges. However, their widespread use is hindered by the limitations of the currently available functional materials. This study explores the <i>in situ</i> hydrothermal growth of 1T-phase MoS₂ directly onto the surface of carbon nanofibers (CNFs), forming 3D hierarchical nanostructures with potential for both supercapacitor and HER applications. The effect of reaction time on the thickness of the 1T-MoS₂ outer layer is systematically investigated, revealing a stepwise relationship between layer thickness and reaction time. The resulting 1T MoS₂/CNFs hybrids, with varying MoS₂ layer thicknesses, exhibit distinct specific capacitance behaviors under varying scan rates, due to differences in conductivity and ion diffusion distances. Post-electrochemical testing analysis reveals 1T-MoS₂ inherent instability, which, rather than transitioning to the 2H-phase, predominantly oxidizes to form molybdenum oxides. Despite this limitation, the hybrids demonstrate promising performance in HER electrocatalysis, with thicker MoS₂ layers offering more active sites, despite an unfavorable trade-off in conductivity. This study provides a mechanistic understanding of 1T-MoS₂/CNFs nanohybrids in electrochemical applications, highlighting the interplay between MoS₂ phase composition, thickness and electrochemical performance. Our findings underscore both the potential and challenges in optimizing these nanohybrids for enhanced energy storage and hydrogen evolution, paving the way for future advancements in multifunctional energy materials.