BiOCl nanosheets are synthesized by a hydrothermal method according to reference . Briefly, 2 mmol of Bi(NO3)3•5H2O (Aldrich, 99.99%) were dissolved in 50 mL of an aqueous D-mannitol (Aldrich, 98%) solution (0.1 mol L -1 ) followed by 1 hour of agitation. After that, 10 mL of saturated aqueous NaCl (Aldrich, 99%) solution was added dropwise to the above solution under stirring. Subsequently, this mixture was transferred to a 100 mL Teflon-lined autoclave and heated at 160 °C for 3 h. The precipitates were washed with water and ethanol for 7-8 times and then collected after drying at 60 °C for overnight. For simplicity, the as-prepared, pristine sample is denoted as BOC-S0.