Highly Selective CO₂ Gas Sensing Properties of CaO-BaTiO₃ Heterostructures Effectuated through Discretely Created <i>n‑n</i> Nanointerfaces

Globally recognized for its role as an occupational hazard, carbon dioxide (CO₂) detection and monitoring is essential in agriculture, chemical manufacturing, and healthcare/clinical-oriented applications. Although, optical and chemical gas sensors are available commercially, current gas sensing technologies involving selective monitoring of CO₂ at lower detection limits specifically for industrial conditions still remains a formidable challenge. Herein, we present a simple strategy for highly selective CO₂ detection using an inexpensive transducer platform based on reversible chemisorbed carbonation between CO₂ and CaO-BaTiO₃ heterostructures. Microsensors showed an optimum sensitivity of 65% toward 1000 ppm of CO₂ gas and superior selectivity when operated at 160 °C. Such a remarkable sensing performance originates from the discretely created <i>n-n</i> nanointerfaces and conveniently actualized staggered energy band positions that promote favorable charge transfer upon exposure to CO₂ gas molecules even at parts per million levels. Reversible sensing phenomenon is demonstrated using <i>operando</i> time-resolved diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and correlated with energy band alignment determined from the ultraviolet diffuse reflectance (UV-DRS) spectra to propose the sensing mechanism