Brønsted-acid sites induced photocatalytic cracking of low-polarity polyethylene plastics

Polyolefins such as polyethylene (PE) are one of the largest-scale synthetic plastics and play a key role in modern society. However, polyethylene is extremely inert to chemical recycling owing to its lack of chemical functionality and low polarity, making it one of the most challenging environmental hazards globally. Herein, we developed a phosphorylated CeO2 catalyst by an organophosphate precursor and featured efficient photocatalysis of low-density polyethylene (LDPE) without the acid or alkaline pre-treatment. Compared to pristine CeO2, the surface phosphorylation allows to introduce Brønsted acid sites, which facilitate to form carbonium ions on LDPE via protonation. In addition, the suitable band structure of the phosphorylated CeO2 catalyst enables efficient photoabsorption and generates reactive oxygen species, leading to the C-C bond cleavage of LDPE. As a result, the phosphorylated CeO2 catalyst exhibited an outstanding carbon conversion rate of >94% after 48 h of photocatalysis under 50 mW/cm2 of simulated sunlight, with a high CO2 product selectivity of >99%. Furthermore, the PE microparticles with sizes larger than 10 μm released from LDPE plastic wrap were directly and completely degraded by photocatalysis within 12 h, suggesting an attractive and environmentally benign strategy of utilizing solar energy-based photocatalysis for reducing potential hazards of LDPE plastic trashes.