Abstract:

In order to solve the pollution caused by nitrogen oxides（NO _x ） to the environment， non-metallic boron-doped nitrogen-rich carbon nitride（B/C₃N₅） photocatalytic materials were prepared by evaporation solvent-high temperature thermal polymerization.The phase，characteristic functional groups，elemental composition，spectral absorption range and photoelectron-hole recombination of B/C₃N₅ photocatalytic materials were characterized by X-ray diffraction（XRD），Fourier transform infrared spectroscopy（FT-IR），X-ray photoelectron spectroscopy（XPS），ultraviolet-visible diffuse reflectance spectroscopy（UV-vis DRS），steady-state fluorescence spectroscopy（PL） and electrochemical impedance spectroscopy（EIS）.B/C₃N₅ photocatalytic material（CBCN） was loaded on concrete as a carrier for photocatalytic degradation of NO _x .The results showed that the doping of non-metallic B broadened the spectral absorption range，realized efficient photo-generated carrier separation，reduced the charge mass transfer resistance，and improved the photocatalytic performance.B/C₃N₅ showed significantly better photocatalytic degradation of NO _x than pure C₃N₅，and had good stability.The non-metallic B-doped 3%（mass fraction） B/C₃N₅ photocatalytic material showed the most excellent NO _x degradation activity.The highest degradation rate of NO _x reached 93.98%，and the degradation rate of NO _x still reached 92.94% after 5 cycles.Within 120 min of simulated sunlight irradiation，the highest photocatalytic degradation rates of NO _x by CBCN with curing cycles of 7 d and 28 d reached 77.22% and 84.27%，respectively.When the doping amount of B/C₃N₅ photocatalytic material was 6%（mass fraction），the compressive strength of CBCN with curing period of 7 d and 28 d was the highest，which was 8.29 and 13.96 MPa，respectively.The doping of B/C₃N₅ photocatalytic material effectively improved the compressive strength of concrete.

Key words: B/C₃N₅, concrete, photocatalysis, nitrogen oxides, compressive strength