Unraveling the Synergy of Interfacial Engineering in In Situ Prepared NiO/NdNiO3 for ppb‐Level SO2 Sensing: Mechanistic and First‐Principles Insights

Abstract Interfacial engineering of semiconductor metal oxides offers a plethora of features to overcome the limitations of chemiresistive gas sensors, thereby increasing their practical viability. Herein, the SO 2 sensing characteristics of NiO are modulated through the incorporation of NdNiO 3 , via a facile in situ synthesis of NiO/NdNiO 3 nanostructures that significantly enhance the sensor performance. To this end, systematic control of the Nd/Ni molar ratio is employed during the synthesis of NiO/NdNiO 3 , enabling the regulation of structural properties and interfacial interactions. The optimized NiO/NdNiO 3 ‐based sensor demonstrates superior SO 2 detection at 140 °C, outperforming pristine NiO, owing to tunable charge carrier dynamics at the heterointerface during gas adsorption. The sensor showcases an extensive dynamic response range from 450 ppb to 200 ppm and an impressive detection limit (320 ppb), along with remarkable selectivity and excellent stability. First‐principles calculations reveal NiO and NdNiO 3 play distinct roles in SO 2 adsorption, with NiO functioning as the receptor, selectively interacting with SO 2 through dissociated oxygen, and NdNiO 3 serving as the transducer, facilitating signal conversion by inhibiting oxygen dissociation. Additionally, the designed portable, threshold‐triggered sensor prototype, integrating the developed NiO/NdNiO 3 sensor with enhanced SO 2 detection, presents a promising avenue for applications in industrial and environmental monitoring.