Plasma-Enabled Process with Single-Atom Catalysts for Sustainable Plastic Waste Transformation

The escalating issue of plastic waste generation has prompted the search for an effective solution to address these challenges. In this study, we present a novel plasma-enabled strategy for the rapid breakdown of various types of plastic wastes, including mixtures, into high-value carbon nanomaterials and hydrogen. The H₂ yield and selectivity achieved through the implemented catalyst-free plasma-enabled strategy are 14.2 and 5.9 times higher, respectively, compared to those obtained with conventional thermal pyrolysis under similar conditions. It is noteworthy that this catalyst-free plasma alone approach yields a significantly higher energy yield of H₂ (g_H2/kWh) compared to other pyrolysis processes. By coupling plasma pyrolysis with thermal catalytic process, employing of 1 wt . % M/CeO₂ (M=Fe, Co, and Ni) atomically dispersed catalysts can further enhance hydrogen production. Specifically, the 1 wt . % Co/CeO₂ catalyst demonstrated excellent catalytic performance throughout the 10 cycles of plastic waste decomposition, achieving the highest H₂ yield of 46.7 mmol/g_plastic (equivalent to 64.4 % of theoretical H₂ production) and nearly 100 % hydrogen atom recovery efficiency at the 7^th cycle. Notably, the H₂ yield achieved over the atomically dispersed Fe on CeO₂ surface (1 wt . % Fe/CeO₂) in the integrated plasma-thermal catalytic process is comparable to that obtained with Fe particles on CeO₂ surface (10 wt . % Fe/CeO₂). This outcome, demonstrated with single-atom catalysts, offers a promising avenue for cost-effective and efficient chemical plastic recycling. Through a combination of experimental and computational efforts, we have provided an in-depth understanding of the catalytic mechanisms of the investigated single atom catalysts in the developed plasma-enabled process. This innovative and straightforward approach provides a promising and expedient strategy for continuously converting diverse plastic waste streams, including mixed and contaminated sources, into high-value products conducive to a circular plastic economy.