Novel Z-Scheme Ag/TiO2/AgMIL-101(Cr) as an efficient photocatalyst for nitrogen production from nitrate

Z-Scheme Ag/TiO2/AgMIL-101(Cr) was prepared by co-doping Ag and TiO2 with AgMIL-101(Cr) via solvothermal synthesis combined with sol-gel method. Ag and anatase TiO2 nanoparticles were well dispersed on the surface of AgMIL-101(Cr) with octahedral structure. 5 wt% Ag and 50% TiO2 co-doping on the AgMIL101(Cr) (Ag5T50Ag5M) exhibited large specific surface area (346.5 m(2).g(-)(1)) and narrow band gap 2.16 eV. Only 10 min of UV light irradiation resulted in the conversion of nitrate and nitrogen selectivity up to 100% over Ag5T50Ag5M. After 5 cycles of nitrate removal, the conversion of nitrate remained 90% indicating that catalyst had stable reusability. Moreover, instead of formic acid, ofloxacin (OFX) was used as a hole scavenger to evaluate the ability of Ag5T50Ag5M for the nitrate reduction. The result showed that the concentration of OFX was important factor to affect the conversion of nitrate. Based on the above discussion about the characterization and photocatalytic nitrate reduction, combined with the photoluminescence and electrochemical measurement results, the enhanced conversion of nitrate and nitrogen selectivity was reasonably explained. Finally, the route of electron transfer during the three constituents constructed Z-Scheme system and the mechanism of nitrate reduction to nitrogen was presumed.