Tunable NiOₓ-MoO₃-MoS₂ nanocomposites: synthesis, structural insights, and enhanced photocatalytic performance

We report 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 with mixed Ni valence states and oxygen defects, 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's superior efficiency due to balanced phase composition and efficient radical generation, with rapid adsorption and degradation in the first 5 minutes, 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. The synthesis used a unique sol-gel and annealing method, enabling tunable phase ratios and enhanced photocatalysis, with no prior reports on this ternary system. These findings highlight the role of phase distribution and interfacial chemistry, offering new possibilities for tailoring NMOS NCs for photocatalytic and environmental applications.