Regulating free radical species towards selective photocatalytic acetic acid synthesis from polylactic acid plastic over sulfur-doped BiVO4/In2S3 S-scheme heterojunction

Photocatalytic conversion of polylactic acid (PLA) plastic waste into value-added chemicals offers a promising approach for sustainable development. However, achieving high selectivity toward a desired product in the conversion remains challenging due to uncontrolled formation of oxygenated intermediates. Herein, we demonstrate a highly selective strategy for converting lactic acid (LA) derived from PLA hydrolysis into acetic acid, which is achieved by precisely regulating radical generation using a sulfur-doped BiVO 4 /In 2 S 3 (S-BiVO 4 /In 2 S 3 ) S-scheme heterojunction. DFT theoretical calculations and in-situ electron paramagnetic resonance results reveal that sulfur doping reduces the formation energy of V 4+ from V 5+ in BiVO 4 , facilitating electron transfer and O 2 dissociation. This promotes •OH radical generation via a proton-coupled electron transfer process by supplying protons to lower the •OH formation barrier. Consequently, •COCH 3 intermediates selectively interact with •OH radicals to form acetic acid. The optimized S-BiVO 4 /In 2 S 3 catalyst achieves an acetic acid generation rate of 3.97 mmol g −1 h −1 with an apparent quantum efficiency (AQE) of 1.42 % at 360 nm. Moreover, the acetic acid selectivity at S-BiVO 4 /In 2 S 3 reaches 84.3 %, which is significantly higher than that of its counterpart, pristine BiVO 4 (27.3 %). The present work opens a new avenue for designing efficient photocatalysts to selectively convert waste plastics into value-added products.