Dual-sided Pd functionalization of groove-textured CeO2 hollow microcages boosts room temperature NO2 sensing

Room-temperature (RT) detection of NO 2 remains challenging because low-temperature operation often limits surface reactivity and charge-transport modulation. Here, a noble-metal-decorated hollow cage-like oxide is constructed by integrating a template-assisted route with hydrothermal processing, yielding a cauliflower-like architecture with a high specific surface area and abundant, accessible adsorption sites for NO 2 capture. Surface decoration further enriches oxygen vacancies and enhances the oxygen storage capacity, promoting oxygen activation and NO x surface chemistry under ambient conditions. Meanwhile, the formation of a Schottky barrier between Pd and CeO 2 enhances the conductivity and electron mobility of the composite. As a result, the chemiresistive sensor delivers a response of 32.84 toward 100 ppm NO 2 at room temperature, with a 3 s response and 15 s recovery, while maintaining good selectivity, repeatability, and long-term stability. The device further achieves a 30 ppb detection limit, highlighting this hollow, vacancy-rich microcage platform as an effective strategy for low-power NO 2 monitoring. This work provides a generalizable interface and defect engineering strategy for next-generation RT NO 2 sensors.