Isolated Ni atoms enable alkali-free photoreforming of waste polylactic acid plastic

Although polylactic acid is a promising biodegradable plastic, its slow degradation under natural conditions, microplastic formation, and CO₂ emissions during decomposition undermine its sustainability. Photoreforming offers a promising strategy for polylactic acid conversion; however, current methods suffer from sluggish kinetics and low selectivity. Here, we design a Ni single-atom catalyst anchored on CdS (Ni/CdS) to enable alkali-free photoreforming of real polylactic acid plastic waste under mild conditions. Ni single atom sites facilitate sequential cleavage of α-OH and C_α-H bonds, enabling efficient H₂ evolution and significantly improving the yield and selectivity of polylactic acid conversion to H₂ and pyruvic acid, achieving an apparent quantum efficiency of 46%. Furthermore, we successfully scaled up the synthesis of Ni/CdS and implemented a square-meter-scale reaction system, demonstrating stable outdoor photoreforming of real polylactic acid plastic waste under sunlight. This work paves a promising pathway for solar-driven upcycling of polylactic acid plastic waste.