Heterointerface rich CeO2-MoO2-Mo2C-C nanotube with the optimized composition and electronic structure via in-situ carburization towards highly efficient degradation of organic pollutants

Abstract

The present study reported the construction of MoO₂/Mo₂C incorporated within a carbon matrix (MMC) decorated with CeO₂ nanoflowers to enhance the photocatalytic degradation of tetracycline under visible light irradiation. The MoO₂/Mo₂C-CeO₂ (MMC-CeO₂) nanocomposite (NCs) was synthesized via a chemical co-precipitation method followed by calcination. The formation of nanotube MMC structures and the deposition of CeO₂ nanoflowers were confirmed through SEM and HR-TEM analyses. XRD analysis validated the cubic phase of MoO₂ and the successful integration of CeO₂ over MoO₂/Mo₂C. The mesoporous nature, characterized by an H1 hysteresis loop and a type IV isotherm, was identified using BET and BJH analysis. Photoluminescence spectroscopy and Nyquist plots indicated a reduced charge carrier recombination rate and improved charge separation compared to CeO₂ and MMC. Ligand-to-metal charge transfer in MMC revealed electron migration from oxygen to Mo⁶⁺, as confirmed by prominent peaks in UV-vis absorption spectra. XPS analysis provided insights into the chemical states of elements, with peak shifts elucidating heterojunction formation. The optimized MMC-CeO₂-10 exhibited the highest photocatalytic activity, achieving 91% tetracycline degradation in 180 min, with a regression coefficient of R² = 0.9519 min⁻¹. The impact of various interfering ions and radical formation was investigated. Reusability studies demonstrated sustained photocatalytic efficiency of 89.6% after four cycles, confirming the material’s stability and resistance to photo-corrosion. The intermediates of the photocatalytic degradation reaction were determined using GC-MS/MS analysis and the plausible degradation pathway was proposed. The toxicity of the intermediates were assessed via insilico ECOSAR tool. These findings highlight MMC-CeO₂ as a highly efficient and stable photocatalyst for wastewater treatment applications.