One-pot reflux method synthesis of cobalt hydroxide nanoflake-reduced graphene oxide hybrid and their NOx gas sensors at room temperature

The different morphology cobalt hydroxide (Co(OH)2) nanoflake-reduced graphene oxide (rGO) hybrid were controllably synthesized by one-pot reflux method. The structural and surface properties of the materials were investigated by scanning and transmission electron microscopy, powder X-ray diffraction and Fourier transform infrared spectroscopy. It was found that the nanostructures were actually composed of thin nanosheets or nanopetals, which consisted of many ultrafine nanoparticles with 5–7 nm diameters. The gas-performance results of the composites for NOx demonstrated that they had superior performance compared to the pure α-Co(OH)2, especially the α-Co(OH)2/rGO-10 composite (mass ratio of Co(NO3)2⋅6H2O/GO was 10:1) showed higher NOx gas sensing performance with lower detection limit of 0.97 ppm and high sensitivity of 70% to 100 ppm NOx at room temperature. The mechanism of it was preliminary attribute to the effective combination between α-Co(OH)2 and rGO, which restrained α-Co(OH)2 from growing up and aggregating, The pore structure of composite material could be quickly adsorption gas molecules leading to rapid electron transfer.