Plasmon-Enhanced S-Scheme Ag/ZnAl-MMO Heterojunction for Photothermal Catalytic Conversion of Polylactic Acid Plastic

Abstract Photocatalytic conversion of waste polylactic acid (PLA) plastic is often limited by poor charge separation and sluggish surface kinetics. To overcome this, we developed Ag-loaded ZnAl mixed metal oxides (MMO) with an S-scheme heterojunction. The optimal material achieves near-complete PLA degradation within 4.5 h, showing about twice the activity of pristine ZnAl-MMO. This enhancement arises from the synergy between the S-scheme charge transfer and the localized surface plasmon resonance (LSPR) of Ag nanoparticles. As verified by theoretical calculations and electron paramagnetic resonance (EPR), the S-scheme facilitates spatial charge separation, while Ag LSPR broadens visible-light absorption and induces local heating to accelerate surface reactions. This work offers a simple strategy to convert PLA waste into valuable products, promoting sustainable recycling.