Synthesis and structural insights of tunable NiO_X–MoO₃–MoS₂ nanocomposites with enhanced photocatalytic performance

We report for the synthesis, structural characterization, and photocatalytic activity of NiOₓ-MoO₃-MoS₂ nanocomposites (NCs) with different ratios of MoO₃-MoS₂ (labeled as NMOS, N = NiOₓ, MO = MoO₃, S = MoS₂). NiOₓ nanoparticles (NPs) were synthesized via a sol–gel method and subsequently annealed with different Mo-precursor ratios to form NMOS NCs. Structural analyses (XRD, TEM, XPS, Raman) confirmed a non-stoichiometric NiOₓ core, encapsulated by MoO₃-MoS₂ domains. Optical studies showed band gap tuning from 3.53 eV (NiOₓ) to 2.92 eV (NMOS-III), enhancing visible-light absorption. Photocatalytic activity, evaluated through methylene blue (MB) degradation, revealed NMOS-I exhibited the highest efficiency due to balanced phase composition and efficient radical generation, with rapid adsorption and degradation in the first 5 min, followed by slower equilibrium adsorption. In contrast, excessive Mo-precursor loading in NMOS-III formed a secondary phase (e.g., NiS), leading to recombination losses and reduced efficiency. This work represents the first demonstration of tunable ternary NMOS NCs and elucidates how precise control of phase ratios and heterointerfaces dramatically enhances photocatalytic activity. These findings highlight the role of phase distribution and interfacial chemistry, offering new possibilities for tailoring NMOS NCs for photocatalytic and environmental applications.