Co<sub>3</sub>O<sub>4</sub> Nanosheets Decorated with In<sub>2</sub>O<sub>3</sub> Nanocubes with Exposed {001} Facets for ppb-Level CO Sensing
Bingcai Chen, Pengpeng Li, Lian Sun, Yingde Wang, Bing Wang
Abstract
To selectively detect trace carbon monoxide (CO typically lower than 100 ppb) at low temperature is still a great challenge for chemiresistive gas sensors. In this work, we introduce In2O3 nanocubes with exposed {001} facets to couple with MOF-derived porous Co3O4 nanosheets (NSs) forming p–n heterojunction for trace CO detection. Benefiting from the vacancy storing effect of the sub-valent band on In2O3 nanocube {001} facets and the p–n heterojunction effect, the electron–hole recombination is effectively inhibited, and the carrier lifetime is prolonged. As a result, the prepared CoIn0.1-based gas sensor shows a good selectivity and ultralow detection limitation of 25 ppb toward CO at relatively low temperature of 175 °C. In addition, the CoIn0.1-based CO sensor also exhibits high response (272.89%) and ultrafast response/recovery time (2 s/13 s) to 100 ppm CO, which can be ascribed to the fast gas diffusion in the porous Co3O4 NSs and the high-index facet effect of In2O3 nanocubes. This work provides a method to design and synthesize trace CO gas sensors via modulating the band structure of p–n heterojunctions constructed by two-dimensional metal oxide NSs and oxide-exposed high-index facets.