Co3O4 nanoparticles assembled coatings synthesized by different techniques for photo-degradation of methylene blue dye

Co3O4 nanoparticles assembled coatings have been synthesized by physical (pulsed laser deposition (PLD) and electron beam deposition) and chemical (sol-gel and electroless) techniques. The morphological, structural, and optical properties of all the coatings were analyzed by SEM, XRD, Raman spectroscopy, XPS, and UV-vis spectroscopy. The catalytic activities of the several Co3O4 heterogeneous catalyst coatings have been compared by looking at their efficiency on degradation of methylene blue dye that occurs via photo Fenton reaction in presence of H2O2 or oxone oxidants. The coating synthesized by PLD exhibits the best photo-degradation rate of dye in presence of H2O2 (4h) or oxone (8min). The NPs produced by PLD process exhibit smaller average size (18nm), narrow size distribution (σ=3nm), perfect spherical shape, low degree of agglomeration, and mixed amorphous-nanocrystalline phase. These special features of NPs, along with better visible light absorption, are the main factors responsible for the enhanced photocatalytic activity of the PLD Co3O4 NPs assembled coating. It is also observed that although the concentration of oxone (0.5mM) was very small as compared to H2O2 (100mM) the photo-degradation of MB dye solution is much faster for oxone.