A simple grinding-calcination approach to prepare the Co3O4-In2O3 heterojunction structure with high-performance gas-sensing property toward ethanol

The development of gas sensing devices with high sensitivity, good selectivity and excellent stability is becoming increasingly important since toxic or harmful gases are a threat to human health. Herein, we report a simple grinding-calcination method to prepare high-performance gas sensing materials based on a novel Co3O4-In2O3 heterojunction structure. Particularly, morphological and structural analyses indicate that the n-type In2O3 and p-type Co3O4 semiconductors are successfully combined and form a stable heterojunction structure through only a simple grinding-calcination process, in which electrons transfer from n-type In2O3 to p-type Co3O4 and then combine with holes belonging to Co3O4 nanoparticles, which can explain the formation mechanism of the electron depletion layer or the unique heterojunction structure. Interestingly, the sensing materials based on the Co3O4-In2O3 heterojunction exhibit excellent sensing properties to ethanol. This enhanced sensing performance can be attributed to the electron depletion layer formed at the interface between n-type In2O3 and p-type Co3O4. Particularly, the sensing device based on the Co3O4-In2O3 heterojunction structure with 1 wt% Co3O4 (labeled Co3O4-In2O3 (1%)) in the composite system shows a very high gas response to ethanol (approximately 62.13 at 240 degrees C, which is 1.36 times higher than that of pure In2O3 and 11.4 times higher than that of pure Co3O4). Moreover, the Co3O4-In2O3 (1%) sensing device shows an extremely low detection limit to ethanol (the gas response value can reach up to 4.4 to 5 ppm of ethanol, which is 1.43 times higher than that of pure In2O3). Furthermore, the fast response and recovery time (42 and 92 s, respectively), high selectivity and high stability presented by the Co3O4-In2O3 heterojunction display its great potential in the design of excellent gas sensing materials for practical gas detection.