Z-scheme Ag6Si2O7/CdS/C heterojunction promotes photocatalytic treatment of water-based pollutants

Photocatalytic degradation of organic pollutants offers a potential solution for alleviating water environmental crises, yet traditional photocatalysts suffer from low visible light utilization, poor photocatalyst stability and rapid charge carrier recombination. Herein, we developed a novel Z-scheme Ag₆Si₂O₇/CdS/C heterojunction photocatalyst for the degradation of pollutants in water under visible light. The carbon layer protects CdS from photo-corrosion and promotes electron transfer, and further coupling of Ag₆Si₂O₇ to form Z-scheme heterojunctions can effectively separate electron-hole pairs, thereby significantly enhancing the photocatalytic activity of CdS. Under 60 min of visible light, 20 % Ag₆Si₂O₇/CdS/C achieved 99.4 % rhodamine B (RhB) removal, along with a kinetic constant of 0.070 min⁻¹, which is 16.27 times higher than pristine CdS. In addition, the 20 % Ag₆Si₂O₇/CdS/C have a good removal effect on methyl orange (MO, ∼100 %, 40 min), tetracycline (TC, 99.7 %, 60 min), ciprofloxacin (CIP, 99.5 %, 120 min), phenol (99.6 %, 120 min) and 2,4-dichlorophenol (2,4-DCP, 91.3 %, 120 min). Free radical scavenging tests showed O₂⁻ radicals drive the degradation and the Z-scheme mechanism was illustrated. This study provides an efficient photocatalyst and new ideas for improving visible light utilization and charge separation in photocatalysis.