The visible-light photocatalytic efficiency of BiOCl/Bi2O3 composites was notably enhanced by covering their surfaces with monolayer of WO3. The photocatalytic activity of WO3/BiOCl/Bi2O3 in decomposing gaseous 2-propanol (IP) and aqueous 1,4-terephthalic acid (TPA) under visible-light irradiation (lambda >= 420 nm) was maximized by introducing a 0.6 mol% of WO3 to BiOCl/Bi2O3, whereas further increases of WO3 sharply decreased its activity. This suggests that monolayer coverage of BiOCl/Bi2O3 with molecular WO3 optimizes photocatalytic activity, and therefore, that the role of WO3 is to improve the adsorption affinity of BiOCl/Bi2O3 toward OH-, H2O, and organic species. In the evolution of CO2 from IP, 0.6%WO3/BiOCl/Bi2O3 exhibited 2.7 times the photocatalytic efficiency of bare BiOCl/Bi2O3. Remarkably, its efficiency was estimated to be 1.7 times that of typical N-doped TiO2. Moreover, it was found that the surface coverage of WO3 greatly extended the chemical stability of BiOCl/Bi2O3 during photocatalytic reaction. (C) 2011 Elsevier B.V. All rights reserved.