Tuning oxygen activity via Ni doping in LaFeO3 for staged chemical looping gasification of plastic waste

A novel staged chemical looping gasification (SCLG) process is developed for sustainable production of hydrogen-rich syngas from plastic waste, where precise modulation of oxygen activity in oxygen carriers (OCs) is crucial. Herein, a series of LaFe 1- x Ni x O 3 ( x = 0–0.8) perovskite-type OCs were synthesized and systematically evaluated in the SCLG of polypropylene. The Ni-doped perovskites demonstrated significantly enhanced syngas production compared with undoped LaFeO 3 , with LaFe 0.6 Ni 0.4 O 3 exhibiting the optimum performance. This catalyst achieved a syngas yield of 168.4 mmol/g plastic , together with a CO selectivity of 92.4% and carbon conversion of 91.5%. Notably, it maintained these activities over multiple redox cycles without significant degradation. The optimized oxygen activity achieved through Ni doping originates from the significantly increased concentration of oxygen vacancies, which facilitates the transformation of Fe 2+ to higher valence states (Fe 3+ /Fe 4+ ). This accelerates oxygen migration and promotes the release of lattice oxygen, resulting in greater CO generation during the fuel stage. In addition, Ni doping enhances the oxygen recovery capability of reduced OCs through improved steam adsorption and subsequent dissociation, as further supported by density functional theory (DFT) calculations. This study provides new insights into oxygen activity modulation, advancing the understanding of chemical looping gasification and informing catalyst design strategies for sustainable H 2 -rich syngas production from plastic waste. Ni doping enabled the modulation of oxygen activity in LaFeO 3 during the staged chemical looping gasification of polypropylene. • A novel staged chemical looping gasification process for plastic waste was developed. • Ni-doped LaFeO 3 exhibited improved catalytic activity and redox performance. • Optimal Ni doping significantly enhanced lattice oxygen release. • DFT calculations revealed that Ni doping improves the oxygen recovery ability. • Consistent H 2 -rich syngas production, up to 165 mmol/g plastic , was achieved over multiple cycles.