Effect of Precursors’ Concentration on Structural and Electronic Properties of Ammonium Ions (NH 4+ ) Intercalated 1T/2H Phase MoS 2

In this study, we have prepared a mixed phase of 1T/2H-MoS₂ nanoflowers using a simple hydrothermal approach without loading any additional catalyst. The ammonium (NH⁴⁺ ) ion intercalation has been induced to insert the 1T phase, with an increase in Mo precursor i.e., ammonium molybdate tetrahydrate concentration in an order of 1M, 1.4M, and 1.8M to obtain the mixed phase of 1T/2H-MoS₂ . The synthesis confirmation and structural properties of mixed-phase has been investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The morphology of 1T/2H-MoS₂ clearly shows the reduction in grain size and an increase in active sites due to the change in morphology from the crumbled nanoflowers to the agglomerated tiny pin-like microstructures. XRD and Raman confirm the presence of mixed phase and it has been observed that crystallite size and the interplanar distance increase with the increase in NH4+ ions molar concentration (1-1.8 M). The mixed phase of 1T/2H-MoS₂ shows high absorbance in the visible region due to the presence of the metallic behaviour and a lowering in the bandgap (1.9 eV to 1.5 eV) is also clearly observed with the increase in concentration. From XPS, it has been concluded that the concentration of the 1T phase in the mixed 1T/2H-MoS₂ can be controlled by optimizing the concentration of the precursor during preparation such as with 1.8 M concentration, the developed 1T character is around 45.8 %. The mixed phase 1T/2H-MoS₂ is found to be a suitable candidate for gas sensing due to its improved interplanar spacing, adjustable bandgap, and enhanced active sites.