Facile synthesis of the Z-scheme graphite-like carbon nitride/silver/silver phosphate nanocomposite for photocatalytic oxidative removal of nitric oxides under visible light.

In this study, a novel ternary Z-scheme Graphite-like Carbon Nitride (g-C3N4)/Silver (Ag)/Silver Phosphate (Ag3PO4) photocatalyst was designed and prepared using a two-step method (sodium chloride (NaCl) template-assisted strategy plus selective deposition). Its photocatalysts performance against removing 400 ppm of Nitric Oxides (NOx) was then investigated. We found 50 wt% g-C3N4/Ag/Ag3PO4(AP-CN 2:1) catalyst removes up to 74% of NO in 90 min under the illumination of visible light (>420 nm), which is respectively 3.5 and 1.8 times higher than using g-C3N4 or Ag3PO4, alone. This improved performance was attributed to the formation of Z-scheme g-C3N4/Ag/Ag3PO4 heterojunction, driven by the built-in electric field across the g-C3N4/Ag/Ag3PO4 interface. These separated the electron-hole but enhanced the original strong oxidation and reduction performance of related components. The superior performance is also attributed to the improved surface area, enhanced hydrophilicity (H2O2) and better visible-light-harvesting capability of the composite compound. More importantly, the AP-CN 2:1 sample maintained a NO removal rate of more than 73% even after four rounds of recycling. The photocatalytic oxidation removal mechanism was evaluated using the radical-capture experiments, electron spin resonance (ESR) and ion-exchange high-performance liquid chromatography (HPLC) analysis. The findings of this work offer a simple but effective design of a highly reactive and practical ternary Z-scheme heterojunction photocatalysts for the removal of toxic NO.