In-situ synthesized oxygen-vacancy-rich CuO nanosheet arrays for low-temperature ppb-level NO2 sensing

Abstract

Developing a strategy to tailor the morphology and sensing properties of CuO nanosheets array for low-temperature, ppb-level selective Nitrogen dioxide (NO2) detection is of great significance as it represents a key step toward addressing challenges related to air quality improvement, human health protection, and environmental sustainability. In this work, CuO nanosheets were synthesized via a seed-induced hydrothermal in-situ method, which lead to a small thickness of 16.72 nm, and a high concentration of oxygen vacancies. The as-prepared CuO nanosheets exhibited a high response of 4.65 with short response and recovery times of 59 s and 72 s, respectively, toward 100 ppb NO2 at 75℃. The sensing mechanism was investigated using electron paramagnetic resonance (EPR), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Density functional theory (DFT) calculations were employed to elucidate the selectivity of NO2 over interfering gases. The in-situ grown CuO nanosheets (comparable to the Debye length) provided expanded reaction interfaces and efficient electron transport channels upon exposure to NO2, which facilitated enhanced interactions between the gas molecules and active sites, improving the sensing response. Moreover, the high concentration of oxygen vacancies acted as reactive centers that effectively reduced the reaction energy barrier, enabling ppb-level, highly sensitive, and selective NO2 detection at low operating temperatures. Overall, this work provides a new material for gas sensing, which promises advancements in high-performance, low-temperature NO2 sensors