High performance, recoverable Fe3O4ZnO nanoparticles for enhanced photocatalytic degradation of phenol

In this paper, a novel type of magnetic photocatalyst, made of Fe3O4ZnO hybrid nanoparticles, was prepared and characterized using various analytical instruments. Upon the degradation of phenol in water, the hybrid nanoparticles demonstrated significantly enhanced photocatalytic activity, achieving a phenol degradation efficiency of 82.3%, in comparison with that of 52% by the pure ZnO nanoparticles. A reduced photoluminescence in the hybrid nanoparticles revealed the suppressing effect of the hybrid nanoparticles on the recombination of photoinduced electron–hole pairs. A hypothesized reaction mechanism was presented, showing the possible presence of free iron ions that can act as an electron-trapping site to prevent the fast recombination of photogenerated charge carriers, therefore improving the photocatalytic properties. The stability and the recoverability of the hybrid nanoparticles were also investigated. A recovering yield of 89% was achieved. The strong photocatalytic activity was well maintained after three cyclic treatments, indicating both good recoverability and high performance of the novel photocatalyst. Photocorrosion caused loss of ZnO and Fe3O4 in the recycled hybrid nanoparticles was noticeable. Whilst the loss of ZnO might have led to the reduced photoreactivity of the recycled nanoparticles, the dissolution of iron ions could be critical for the enhanced overall photocatalytic properties of Fe3O4ZnO.