Facile hydrothermal synthesis of rod-like nanostructure NiO/CuO for highly selective low-temperature H2S sensing

Abstract

In the present study, NiO/CuO nanostructures were synthesized using a cost-effective, straightforward hydrothermal method at a molar Ratio of 1:1, followed by calcination. The structural, morphological, and optical properties were analyzed using XRD, FTIR, UV-Vis, FE-SEM, EDX-mapping, and HR-TEM-SAED. XRD analysis confirmed the successful synthesis of the core-shell nanostructures, with the XRD spectrum showing diffraction peaks of cubic NiO and the monoclinic phase of CuO. The morphology of the nanostructures, as determined by HR-TEM, was confirmed to be rod-like, with diameters ranging from 6 to 10 nm, and showed well-resolved lattice fringes of both NiO and CuO. The UV-Vis spectrum of the nanostructures exhibited a broad absorption band, enabling their use in photocatalysis across a wide range of light. Moreover, the synthesized NiO/CuO nanomaterials were evaluated for potential gas-detection applications, and their gas-sensing properties were compared with those of NiO and CuO. The nanostructures sensor exhibited high selectivity to H₂S, with a response of over 90% at an optimal operating temperature of 90 °C. This excellent performance with rapid response and recovery behaviour is due to the synergistic effect of the NiO/CuO nanostructures. This phenomenon enhances charge separation and transport, thereby improving the material's sensitivity and selectivity. The results indicate that the NiO/CuO nanostructures are very promising for potential gas-sensing applications.