Mechanism of Oxygen Carrier Poisoning and Rational Design in Chemical Looping Combustion: A Review

Chemical looping combustion (CLC) is a promising technology for low-emission energy conversion because it enables the inherent separation of CO2 from the combustion products. However, contaminants released from complex fuels, including nitrogen, sulfur, chlorine, arsenic, and mercury-containing species, can induce the deactivation and poisoning of oxygen carriers (OCs), thereby compromising their long-term redox performance and hindering the practical deployment of CLC. This review critically examines the molecular-level interactions between representative pollutants and commonly investigated OCs by integrating insights from density functional theory calculations with relevant experimental observations. The principal poisoning pathways are identified as the occupation or blockage of redox-active sites, consumption or redistribution of lattice oxygen, formation of stable surface compounds, and pollutant-induced structural or phase transformations. Particular attention is given to the roles of oxygen vacancies, surface electronic structure, lattice oxygen mobility, and competitive adsorption in determining the reactivity and stability of OCs. On the basis of these mechanistic insights, three classes of strategies for developing poisoning-resistant OCs are summarized: structural engineering to establish physical and chemical barriers; compositional and doping modifications to regulate oxygen transport, defect chemistry, and pollutant adsorption; and the incorporation of competitive or sacrificial additives to mitigate multipollutant interactions. This Review provides a mechanistic framework for understanding pollutant-induced OC deactivation and offers guidance for the rational development of OCs with high redox activity, structural stability, and broad-spectrum resistance to poisoning.