Highly selective room temperature detection of NO2 enabled by vanadyl oxygen vacancies in novel bilayer V2O5

Abstract

The primary challenge in developing a gas sensor is achieving high selectivity for the target gas. Most sensor materials respond to multiple gases, making it difficult to discern between various toxic gases. The present study reports the enhancement of the selectivity towards NO₂ gas by introducing vanadyl oxygen (O_I) vacancies in novel 2D V₂O₅. The chemical exfoliation process, which is utilized in the present study to synthesize bilayer nanosheets of V₂O₅, intrinsically generates O_I vacancies. The presence of O-vacancy defects, predominantly O_I vacancies, in the sample is confirmed using X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. The bilayer 2D V₂O₅ showed a highly selective chemiresistive response towards NO₂ gas at room temperature unlike normally observed higher temperature sensor response by V₂O₅, typically above 100 °C. Along with the effect of high surface to volume ratio, the room temperature gas sensing performance by 2D V₂O₅ stems from the presence of O_I vacancy defects and the consequent increase in the surface activity. In addition, the presence of O_I vacancies leads to highly selective response to NO₂, since NO₂ is a highly oxidizing gas with a pair of lone electrons. Hence, the present study is the first to reveal novel bilayer V₂O₅ sensor with a highly selective response to NO₂ at ambient temperature.