Powder X-ray diffraction pattern were recorded on a Bruker D2 PHASER diffractometer using Cu Kα radiation at a scan rate of 0.02° min -1 . BET specific surface area and pore volume were measured on a Tristar 3000 automated gas adsorption system. Transmission electron microscopy (FEI Tecnai 20) was used to observe the morphology and bulk structure of the materials. UV-vis diffuse reflection spectra of BiOCl samples were obtained on a UV-Vis spectrometer (Shimadzu UV-2401, Japan) with BaSO4 as reference. X-ray photoelectron spectra were collected on a Thermo Scientific K-Alpha spectrometer equipped with a monochromic Al K-Alpha X-ray source (hv = 1486.7 eV). The powder samples were mounted on adhesive double-sided conductive carbon tape on substrate or filled into the holes of a homemade Cu powder sample holder. A low energy electron/ion flood gun neutralizer was used to compensate the surface charging. High resolution spectra of Bi, O and Cl elements were averagely scanned for 30 times and their pass energy was set to 50 eV. Spectra were binding energy calibrated by setting the main line of Bi 4f7/2 spectrum to 159.4 eV. All XPS spectra were analyzed and processed by CasaXPS and Origin software. EPR spectra were measured on a Bruker EMXplus X-band spectrometer at room temperature in air at a frequency of 9.460-9.470 GHz in 4 mm thin wall quartz glass EPR tubes (Wilmad).