Hydrothermal synthesis of In2O3 nanocubes for highly responsive and selective ethanol gas sensing

Abstract

Indium oxide nanocubes (NCs) were prepared via a simple, template-free hydrothermal method at low temperature; the so-obtained structures exhibited large surface area (47.67 m2/g) and Barrett−Joyner−Halenda (BJH) adsorption average pore diameter (11.92 nm), both higher than for commercial In2O3 nanoparticles. At the optimal temperature of 300 °C, the In2O3 NCs-based sensor showed a superior response of 85–100 ppm ethanol, 3.4 times higher than that of the commercial one based on In2O3 NPs, and also faster response time (15 s) than the commercial device (60 s). The better sensing performance of the synthesized In2O3 NCs can be attributed to its unique properties that include large BET surface area and BJH adsorption average pore diameter as well as abundance of sharp edges and tips, which result in high surface to volume ratios for the gas adsorption and diffusion processes, facilitating the charge-transfer and sensing reactions at the gas–solid interfaces. In addition, the In2O3 NCs exhibited excellent selectivity to ethanol among other target gases (CO, CH4, CH3CHO, H2, and CH3COCH3). This work provides an effective design pathway for ethanol sensors based on In2O3 NCs.