Design and construction of diverse dual co-catalysts decorated Z-scheme g-C3N4/WO3(002) photocatalyst for converting nitrate and sulfite

Photocatalysis technology is an effective way for converting nitrate (NO 3 − ) and sulfite (SO 3 2− ) in wastewater to pollution-free nitrogen (N 2 ) and exploitable ammonium sulfate ((NH 4 ) 2 SO 4 ). In this study, three novel photocatalysts , Z-scheme (Cu,Cu)/g–C 3 N 4 –(Cu,Cu)-WO 3 (002), Z-scheme (Cu,Ag)/g–C 3 N 4 –(Cu,Ag)-WO 3 (002) and Z-scheme (Cu,Ru)/g–C 3 N 4 –(Cu,Ru)-WO 3 (002), were prepared by photo-assisted electrostatic self-assembly method. The prepared photocatalysts are synthetically characterized by XRD , SEM, TEM, EDX , XPS , DRS, PL , TPR and EIS . The effects of different co-catalyst combinations on the activity and selectivity of the photocatalysts are evaluated. Also, the impacts of simulated solar light irradiation time, NO 3 − initial concentration and cycle times on the conversions of NO 3 − and SO 3 2− are studied. The results display that the Z-scheme (Cu,Ag)/g–C 3 N 4 –(Cu,Ag)-WO 3 (002) photocatalyst can selectively convert NO 3 − to N 2 , while the Z-scheme (Cu,Ru)/g–C 3 N 4 –(Cu,Ru)-WO 3 (002) photocatalyst can selectively convert NO 3 − to NH 4 + . Nevertheless, the Z-scheme (Cu,Cu)/g–C 3 N 4 –(Cu,Cu)-WO 3 (002) photocatalyst has hardly selectivity for conversion of NO 3 − . These three photocatalysts all exhibit relatively strong capabilities for converting SO 3 2− to sulfate (SO 4 2− ) due to the existence of the highly active (002) plane of WO 3 . Finally, the possible mechanisms on the photocatalytic conversions of NO 3 − and SO 3 2− caused by Z-scheme (Cu,M)/g–C 3 N 4 –(Cu,M)-WO 3 (002) (M = Cu, Ag and Ru) photocatalysts are proposed.