Chemically Homogenizing MoO₂ Nanocrystals into Monodispersed Spherical Shapes for Enhanced Cr(VI) Photoreduction

Development of monodispersed crystalline nanoparticles with previously unavailable spherical shapes continues to be a constant theme in a wide range of areas but remains a challenge. On the basis of in situ vulcanization strategy and density functional calculations, we show that the shape evolution of uneven metal oxide nanoparticles can be used to achieve highly crystalline monodispersed oxide nanospheres by taking advantage of the unique lattice mismatch at interfaces between closely packed molybdenum dioxide and layered molybdenum sulfides. The monodispersed MoO2 nanospheres together with the adhered ultrathin MoS2 nanosheets show a surprisingly high photoreduction ability of concentrated Cr(VI), superior to those ever reported for MoO2- or MoS2-containing materials under visible and near-infrared light, most likely due to the merits as represented by the metallic character, high density carrier, near-infrared local surface plasma resonance effect, and enhanced interfacial interactions. In this study, the merits of MoS2/MoO2 are fully utilized and outstanding photocatalytic reduction performances of Cr(VI) are achieved, which opens up exciting prospects for its practical application in photocatalysis. The methodology reported here may provide more opportunities to explore functions of monodispersed crystalline oxide nanospheres.