Boosting the efficient combustion of plastic wastes via tailoring the oxygen vacancies of Ce-Zr solid solution

Abstract

Novel-design catalyst is a promising candidate for the clean combustion of plastic wastes, alleviating the environmental and energy crisis. Herein, Ce-Zr catalysts with different oxygen vacancies were prepared by tailoring the Zr-content to optimize the catalytic performance in plastic wastes combustion. The detailed characterization results confirmed that Zr has been successfully incorporated into CeO2 lattice, which decreased the crystal size and increased the surface area. Moreover, the Zr-doping caused the lattice distortion, i.e., Ce-O around the doped Zr was elongated to compensate the shortness of Zr-O, which made it easy to break and generate oxygen vacancies. DFT calculation results revealed that Ce0.8Zr0.2O2 exhibited a lower energy of oxygen vacancies formation (2.22 eV) and O2 adsorption (-1.20 eV) than that of CeO2 (2.46 eV and −0.42 eV). It indicated that the Zr-doping improved the oxygen vacancies and O2 adsorption of Ce-Zr catalysts. Ce0.8Zr0.2O2 significantly improved plastic wastes combustion at 250 °C, and achieved a conversion of 14.3 %, 21.8 %, 100 %, 22.4 % and 13.7 % for high-density polyethylene, low-density polyethylene, polypropylene, polystyrene and real plastic wastes, which was 2–3 times that of the non-catalytic combustion. This has been attributed to the superiority of Ce0.8Zr0.2O2 in the crystal and texture structure as well as the oxygen vacancies and O2 adsorption, i.e., the improved external surface enhanced the contact with polymer molecules, and the improved oxygen vacancies as well as O2 adsorption provided more active oxygen.