In Situ Polymerization of Polypyrrole and Polyaniline on the Surface of Magnetic Molybdenum Trioxide Nanoparticles: Implications for Water Treatment

Photocatalyst dissolution greatly diminishes the usability of photocatalysts in water treatments. Coating conductive polymers on the surface of photocatalysts can reduce dissolution without compromising the photocatalytic properties of the material. In this investigation, polypyrrole (PPy) and polyaniline (PANI) were used to coat two magnetic MoO₃ nanoparticles with different surface chemistries. The polymer-coated MoO₃@Fe₃O₄ nanoparticles were synthesized by optimizing the mole fractions of PPy or PANI, MoO₃, and Fe₃O₄. The optimized PPy@ MoO₃@Fe₃O₄ (PMF1) and PANI@MoO₃@Fe₃O₄ (PMF2) resulted in 95.39 and 75.98% methylene blue dye removal, respectively. MoO₃ dissolutions of 4.12 and 5.6% were obtained for PMF1 and PMF2, respectively, demonstrating the reduced solubility of the coated nanoparticles as compared to their uncoated counterparts (7.87% for MF1 and 18.1% for MF2). In situ small-angle neutron scattering (SANS) was utilized to investigate the polymerization kinetics of PPy and PANI on nanoparticles. The results revealed that an increase in base material oxygen vacancies resulted in the reduction of both the polymer size and the polymerization rate. This study demonstrated that SANS provides valuable insights into the polymer growth mechanisms on nanoparticle surfaces.