Phenyl Hypophosphorous Acid‐Assisted Synthesis of Carbon‐Modified Anatase‐Brookite Bicrystal TiO 2 Nanoparticles with Enhanced Visible‐Light Photocatalytic Performance

Carbon‐modified anatase‐brookite bicrystal TiO 2 nanoparticle (C/TiO 2 ) photocatalysts were successfully synthesized by a facile hydrothermal method using phenyl hypophosphorous acid (PA) as a ligand to mediate the physicochemical properties and as a source of carbon. The carbon species were in situ formed and loaded on TiO 2 surface via carbonization of PA. The characterization results show that the morphology, phase structure, crystal size, chemical states of elements and photocatalytic activity of the C/TiO 2 vary with the amount of PA used. The photocatalytic performance of C/TiO 2 is significantly improved compared with pure TiO 2 because (1) carbon decoration of TiO 2 surface extends the light absorption to the visible‐light range; (2) charge transfer between anatase and brookite nanocrystals increases the quantum efficiency; and (3) small C/TiO 2 nanocrystals yield stronger adsorption capability resulting in an increase in photocatalytic activity. Visible‐light photocatalytic degradation of methyl orange (MO) by the C/TiO 2 photocatalyst was successfully achieved. The MO concentration was reduced by 78 % after exposure to visible light for 180 min. The C/TiO 2 photocatalyst was highly stable after four successive experimental runs.