Facile synthesis of La2O2CO3 nanoparticle films and Its CO2 sensing properties and mechanisms

In this paper, we presented a simple method to fabricate size-controlled La 2 O 2 CO 3 nanoparticle by annealing La(OH) 3 nanocrystallines in air atmosphere. The microstructures of the samples were analyzed by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and scanning electron microscope (SEM). TEM images indicate that the La(OH) 3 precursors consists of uniform ellipsoids with width of 9–15   nm and length of 15–30   nm and La 2 O 2 CO 3 are spheroidal particles with size of 12–25   nm. XRD patterns indicate that La(OH) 3 nanocrystallines are hexagonal phase and transform to monoclinic La 2 O 2 CO 3 after annealing. And then, La 2 O 2 CO 3 nanoparticle is printed on an interdigital electrode as a sensing material for CO 2 detection. La 2 O 2 CO 3 sensor exhibits good cycle stability performance and fast response and recovery (53   s and 120   s) over the wide range of 300–5000   ppm CO 2 in air condition. In addition, we also investigate the effect of oxygen concentration in the background atmosphere on CO 2 response of La 2 O 2 CO 3 sensor. The CO 2 sensing mechanisms for La 2 O 2 CO 3 sensor can be attributed to the interaction of CO 2 with oxygen species on La 2 O 2 CO 3 surface including chemisorption, surface reaction and desorption process, which also can be used to explain other metal oxide based CO 2 gas sensor.