Transition-Metal Doped Ceria Nanoparticles Loaded Metal Oxide Nanofibers: Heightened Surface Activity for Chemiresistors

Oxide semiconductor chemiresistors have shown promise as powerful gas sensors. However, their low surface reactivity limits sensitivity and selectivity. To address this issue, the functionalization of noble metal catalysts on oxide supports has been proposed, but challenges such as scarcity, agglomeration, and poisoning effects hinder practical application. In this study, we present a solution by introducing the highly promising physical and chemical properties of transition metal-doped cerium oxide (Co-CeO₂) as an alternative catalyst. To achieve uniform functionalization, we propose an elaborate design principle that employs an electrospinning technique to integrate Co-CeO₂ catalysts onto nanostructured metal oxide nanofibers. Through a single-step liquid-phase reaction involving organic solvents, we have developed sub-2 nm-sized Co-doped CeO₂ nanoparticle colloids, which can be conveniently and efficiently used for functionalizing the SnO₂ surface through solution-based electrospinning. The synthesized particles possess distinct physicochemical properties and exhibit active catalytic behavior, characterized by high purity and crystallinity. The resulting composite exhibits superior gas sensing characteristics, specifically for isoprene (C₅H₈), with low detection limit and excellent long-cycling stability. Notably, the high catalytic activities of Co-CeO₂ facilitate the spillover process of chemisorbed oxygen species, resulting in a 27.4-fold higher response towards the target analyte with exceptional selectivity. Furthermore, to gain further insights into the mechanisms behind the chemisorption of oxygen species and selective gas adsorption facilitated by the Co-CeO₂ sensitizers, we employed density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analyses. Altogether, our findings demonstrate the potential of transition metal-doped CeO₂ functionalization for highly sensitive chemiresistive gas sensors.