Highly efficient upcycling of plastic waste upon Bi-modified P-doped g-C3N4: Plasmonic effect-dominated Schottky barrier tuning

Solar-driven upcycling of plastic waste to valuable chemicals provides an economic and low-energy technology to solve the accumulation of plastic waste and environmental pollution problems. However, simply relying on the capacity of single semiconductor system is still limited for high-efficient upcycling activity. Here, a low-cost plasmonic metal Bi-modified P-doped g-C 3 N 4 (Bi/PCN) is firstly reported to apply the conversion of waste plastics (including PE, PP, PVC, PEG, and PAM) under natural environment conditions without adding any cocatalysts or sacrificial agents. TAS and theoretical calculation reveal that the synergistic effect of Bi plasmonic excitation and doped P engineering not only improves light absorption ability, but also tunes interfacial Schottky barrier height (SBH) for the excellent charge separation and transport. The superposed amplification effect of Bi plasmonic excitation originates from hot electron injection, SPR scattering effect, and electromagnetic near-field enhancement. Optimized 1.0 %Bi/PCN composite achieves highly efficient upcycling of PE plastic to HCOOH product as liquid hydrogen storage medium with 1.88 % upcycling efficiency, which is the highest upcycling efficiency upon plasmonic photocatalysts as present. In situ EPR and IR spectra disclose plastics proceed multi-oxidative C C cleavage, where •O 2 and •OH radicals trigger plastic molecule and the intermediates of alkyl peroxide, alkyl radical, and alkoxy radical are successively formed. This work provides a preferable strategy for developing high-performance photocatalysts for upcycling of plastics waste through surface plasmon effect.