Investigation of room temperature humidity sensing performance of mesoporous CuO particles

Uniform mesoporous particles of CuO were synthesized by thermal decomposition of precursor basic copper carbonate (BCC). The precursor was obtained by co-precipitation method using Cu(NO₃)·3H₂O and urea as reactant without any additives. Characterization studies including Fourier transform infrared spectrometry (FTIR), X-ray diffraction analysis (XRD), surface area and pore size analyzer and scanning electron microscopy (SEM) was used to investigate the structural, crystallographic, surface area, pore size distribution and morphological properties of basic copper carbonate and CuO. The particles were spherical in shape with uniform sizes. However, the surfaces of basic copper carbonate particles were smooth while CuO particles were of porous appearance. Additional physical characterization revealed that CuO was of mesoporous nature with surface area and average pore diameter 56.25 m²/g and 32–37 nm, respectively. The calcined CuO was fabricated for room temperature humidity detection. The material exhibited reproducible, stable, highly sensitivity and selective response towards humidity with response and recovery time less than 1 s each. The sensing mechanism was proposed to be based on protonic model wherein the generation of protons (charge carriers) reduced the sensor resistance due to their hopping from one active site to another while the capacitance enhanced due to increase in the dielectric constant of the humid sensing layer.