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　O2　evolution　efficiencies　over　the　BiVO4　nanoparticles　under　visible-light　(λ　＞　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　O2　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.　©　2008　Elsevier　B.V.　All　rights　reserved.