Monoclinic BiVO4 nanoparticles were prepared through a homogeneous co-precipitation process. The products calcined at different temperatures were characterized by X-ray diffraction, transmission electron microscopy and UV-vis diffused reflectance spectroscopy. The photocatalytic O-2 evolution efficiencies over the BiVO4 nanoparticles under visible-light (lambda > 420 nm) irradiation were also investigated comparatively by using AgNO3 and Fe(NO3)(3) as sacrificial reagents. Experimental results indicate that AgNO3 is a more effective sacrificial reagent for the photocatalytic O-2 evolution over BiVO4 than Fe(NO3)(3) due to the efficient separation of the photogenerated electron-hole pairs at the Ag/BiVO4 interfaces, but the BiVO4/Fe(NO3)(3) system is more promising in the aspect of practical applications due to its more steady photoactivity and more convenient reactivation of the photocatalyst. (C) 2008 Elsevier B.V. All rights reserved.