A direct polymeric carbon nitride/tungsten oxide Z-scheme heterostructure for efficient photocatalytic hydrogen generation via reforming of plastics into value-added chemicals

To promote charge transfer and separation for efficient photocatalysis, a direct Z-scheme heterostructure was constructed by coupling polymeric carbon nitride (PCN) and WO₃. Interestingly, the obtained PCN/WO₃ Z-scheme heterostructure could photocatalytically produce hydrogen and value-added chemicals (e.g., formate and acetate) by reforming of plastic polylactic acid (PLA) in alkaline aqueous condition. By optimizing WO₃ contents and reaction conditions, the obtained PCN/WO₃ heterostructure exhibits much increased photocatalytic activity for PLA photoreforming under visible light, with hydrogen evolution rate reaching 402.90 μmol·g⁻¹·h⁻¹, which is 3.5 times that of PCN. It is revealed that the Z-scheme charge transfer between PCN and WO₃ mainly contributes to the promoted charge separation and thus the improved photocatalytic activity. Moreover, with h⁺ and ·OH experimentally evidenced as the predominant active species, a possible reaction pathway for the reforming of PLA into value-added chemicals (e.g., formate and acetate) over PCN/WO₃ Z-scheme heterostructure is cleared by monitoring the reaction intermediates and radicals. This work paves a carbon neutrality and scalable route toward the synergistical production of hydrogen and value-added chemicals by utilizing and recycling plastic waste.