Cerium oxide nanoparticles (CeNPs) are versatile materials with unique and unusual properties that vary depending on their surface chemistry, size, shape, coating, oxidation states, crystallinity, dopant, and structural and surface defects. This review encompasses advances made over the past twenty years in the development of CeNPs and ceria-based nanostructures, the structural determinants affecting their activity, and translation of these distinct features into applications. The two oxidation states of nanosized CeNPs (Ce³⁺/Ce⁴⁺) coexisting at the nanoscale level facilitate the formation of oxygen vacancies and defect states, which confer extremely high reactivity and oxygen buffering capacity and the ability to act as catalysts for oxidation and reduction reactions. However, the method of synthesis, surface functionalization, surface coating and defects are important factors in determining their properties. This review highlights key properties of CeNPs, their synthesis, interactions, and reaction pathways and provides examples of emerging applications. Due to their unique properties, CeNPs have become quintessential candidates for catalysis, chemical mechanical planarization (CMP), sensing, biomedical applications, and environmental remediation, with tremendous potential to create novel products and translational innovations in a wide range of industries. This review highlights the timely relevance and the transformative potential of these materials in addressing societal challenges and driving technological advancements across these fields.

It has been very difficult to remove smaller ceria particles from silicon dioxide surfaces. One of the likely reasons is that the smaller ceria particles with a higher surface concentration of Ce³⁺ are more strongly coupled with silicon dioxide surfaces via strong Ce-O-Si bonding. Here, we show that some equimolar solutions containing H₂O₂ and either NH₄OH or KOH, aided by ultrasonic cleaning, and at high pH can almost completely remove even 10 nm sized ceria particles from silicon dioxide film surfaces. The particles on the oxide surface before and after cleaning were imaged using atomic force microscopy and counted. The optimal composition of H₂O₂-NH₄OH solutions was identified by investigating ten solutions with different compositions using an augmented simplex-centroid method along with four H₂O₂-KOH solutions. Equimolar mixtures of H₂O₂ and NH₄OH or KOH with the highest possible perhydroxyl ion concentration [HO₂⁻] showed ∼99% cleaning efficiency for 10 nm ceria particles. We propose that the strong Ce-O-Si bonding can be ruptured effectively by the nucleophile HO₂⁻, formed by the decomposition of H₂O₂ in the high pH environment, and show that [HO₂⁻] is highest in equimolar solutions. The cleaning efficiencies for 10 nm, 30 nm and 90 nm particles correlate very nicely with [HO₂⁻].

Lithium sulfur (Li-S) batteries have drawn much attention as next-generation batteries because of their high theoretical capacity (1672 mAh g−1), environmental friendliness and low cost. However, several critical issues, which are mainly associated with the polysulfide shuttling effect, result in their poor electrochemical performance. Carbon-modified separators have been introduced to attempt to address these systemic challenges. However, this approach focused only on the suppression of dissolved polysulfides on the cathodic side without considering the further entrapment of polysulfides on the anodic side. In this study, we first designed a multifunctional trilayer membrane comprising a carbon layer and a boron nitride (BN) layer to facilitate the electrochemical performance of Li-S batteries and protect the Li anode from unexpected side reactions. When a BN-carbon separator was employed, the sulfur cathode delivered stable capacity retention over 250 cycles and an excellent specific capacity (702 mAh g−1) at a high current density (4 C). The BN-carbon separator also facilitated the uniform plating/striping of Li and, thus, suppressed the severe growth of dendritic Li on the electrode; this led to the stable operation of the Li anode with a high Coulombic efficiency and improved cycling performance.