Copper Oxide Nanorod/Reduced Graphene Oxide Composites for NH₃ Sensing

The NH₃ sensing performance of copper oxide (CuO) nanorods can be enhanced with reduced graphene oxide (rGO) composites (i.e., CuO:rGO) due to their favorable Fermi level alignments and improved carrier mobility. However, the conductivity and the active sites in CuO:rGO are highly determined by the preparation techniques. Hence, we attempt to unravel the role of different chemical routes (wet chemical synthesis and hydrothermal preparation techniques) on the NH₃ sensor device performance of CuO:rGO. Morphological imaging reveals the formation of 1D structures in both preparation techniques, and the role of graphene oxide on the evolution of CuO nanorods is discussed. First-principles calculations probe the interactions between CuO:rGO and NH₃, and the structure is optimized for the most stable configuration. The absorption binding energies of the CuO:rGO–NH₃ systems are measured to be 1.36 eV, which is much higher than those of the metal–rGO composites. For 50 ppm of NH₃, the sensor response is measured to be 3.87 and 6.29 for chemically and hydrothermally synthesized CuO:rGO, respectively. The enhanced response of hydrothermal CuO:rGO is due to the more active sites induced on the CuO nanorod surface by rGO and the favorable band bending at the rGO–CuO interface.