Oxygen-Vacancy-Mediated Large Binding Energy Exciton Dissociation in Nb₃O₇(OH) Nanorods with High Electron Mobility for CO₂ Photoreduction

Abstract

Despite the excellent performance of Nb 3 O 7 (OH) in dye-sensitized solar cells and catalysis, its charge separation, transport, and structural properties remain poorly understood. Herein, the Nb 3 O 7 (OH) nanorods were prepared, and their structural characteristics, optoelectronic properties, and carrier mobility were also analyzed and investigated through a series of complex characterizations. Theoretical prediction suggested that the exciton binding energy of Nb 3 O 7 (OH) could be as high as 100.49 meV. The temperature-dependent photoluminescence (PL) of Nb 3 O 7 (OH) nanorods revealed two activation energies, and a higher proportion of long-lived components observed in the photoluminescence decay indicated effective electron trapping. That is, two energy states were present, hindering photogenerated charge recombination and promoting photocatalytic action. Current−voltage characteristics of the Nb 3 O 7 (OH) nanorod film were analyzed, revealing an ultrahigh carrier mobility of ∼310 cm 2 /V•s, ensuring fast and efficient electron transfer. Furthermore, Nb 3 O 7 (OH) nanorods were employed to reduce CO 2 , resulting in the effective production of CO and CH 4 . Overall, considering the presence of hydroxyl pairs on the surface of Nb 3 O 7 (OH), which facilitate the formation of the frustrated Lewis acid−base pairs and the activation of CO 2 , together with its effective electron trapping and charge transport, give Nb 3 O 7 (OH) nanorods a promising potential for CO 2 reduction. KEYWORDS: Nb 3 O 7 (OH), exciton binding energy, charge transport, CO 2 photoreduction, frustrated Lewis pairs