Review of Shape-Controlled CeO₂ Nanocatalysts for Purification of Auto-Exhaust Pollutants

CeO2 (cerium dioxide or ceria) is a versatile material for industrial catalysis because of its reversible Ce4+/Ce3+ redox pair and tunable oxygen vacancies. Purification of air pollutants released from vehicles and stationary chemical industries is one of the imperative catalytic applications of CeO2. In this regard, significant efforts have been made to improve the properties of CeO2 by precisely controlling its' particle shape. This fascinating shape-controlled strategy can stabilize the surface-enriched crystal facets with excellent redox properties, abundant surface oxygen vacancies, enhanced active-site accessibility, and high catalytic activities. The synergistic effect of doping and deposition of transition metals in improving the structure-activity properties of shape-controlled ceria is also unraveled for air pollution control. Thus, this review aims to summarize and elucidate the advances in the field of catalytic air pollution control using shape-controlled ceria-based nanomaterials. The adverse effects of four types of air pollutants, namely carbon monoxide, soot particulates, nitrogen oxides, and volatile organic compounds, while emphasizing the drawbacks and challenges associated with the current technologies were briefly provided. The role of various doped metals (Zr, Ti, Mn, Co, Fe, Ni, etc.) and deposited metals (Au, Pt, Pd, Ru, Ag, Cu, Mn, etc.) associated with the well-defined morphologies (rods, cubes, tubes, polyhedra, spheres, fibers, etc.) of ceria for air pollution control was meticulously discussed. We hope that this timely important review can provide promising strategies for the rational design of advanced ceria-based catalysts not only for air pollution control but also for important energy-related applications.