Heterostructural CuO–ZnO Nanocomposites: A Highly Selective Chemical and Electrochemical NO₂ Sensor

Abstract

A simple one-step chemical method is employed for the successful synthesis of CuO(50%)–ZnO(50%) nanocomposites (NCs) and investigation of their gas sensing properties. The X-ray diffraction studies revealed that these CuO–ZnO NCs display a hexagonal wurtzite-type crystal structure. The average width of 50–100 nm and length of 200–600 nm of the NCs were confirmed by transmission electron microscopic images, and the 1:1 proportion of Cu and Zn composition was confirmed by energy-dispersive spectra, i.e., CuO(50%)–ZnO(50%) NC studies. The CuO(50%)–ZnO(50%) NCs exhibit superior gas sensing performance with outstanding selectivity toward NO2 gas at a working temperature of 200 °C. Moreover, these NCs were used for the indirect evaluation of NO2 via electrochemical detection of NO2– (as NO2 converts into NO2– once it reacts with moisture, resulting into acid rain, i.e., indirect evaluation of NO2). As compared with other known modified electrodes, CuO(50%)–ZnO(50%) NCs show an apparent oxidation of NO2– with a larger peak current for a wider linear range of nitrite concentration from 20 to 100 mM. We thus demonstrate that the as-synthesized CuO(50%)–ZnO(50%) NCs act as a promising low-cost NO2 sensor and further confirm their potential toward tunable gas sensors (electrochemical and solid state) (Scheme 1).

Decoration of CuO NWs Gas Sensor with ZnO NPs for Improving NO2 Sensing Characteristics

“…The response of the CuO NWs without the heterojunction is similar to what we obtained [36][37][38]. Moreover, our study shows better results on the response of CuO/ZnO heterojunction sensors to NO2 gas, compared to the results of [29] with the same NO2 concentrations. The response of the 0.05 M CuO/ZnO gas sensor to NO2 gas was measured at different NO2 concentrations (1−100 ppm) at 250 °C.…”

“…The response of the CuO NWs without the heterojunction is similar to what we obtained [ 36 , 37 , 38 ]. Moreover, our study shows better results on the response of CuO/ZnO heterojunction sensors to NO 2 gas, compared to the results of [ 29 ] with the same NO 2 concentrations.…”

“…As shown in Figure 5 a, when p-CuO and n-ZnO form a p-n heterojunction, the band curves towards the Fermi level, and a depletion layer is formed due to an electron and hole transfer process. Consequently, the HAL is partially suppressed, thereby increasing the resistance [ 29 , 30 ].…”

Acacia nilotica Pods’ Extract Assisted-Hydrothermal Synthesis and Characterization of ZnO-CuO Nanocomposites

“…96-721-2243, which represents the monoclinic phase of copper oxide. The XRD results confirm that sample ZC100 is formed completely of tenorite, which is pure copper oxide with a monoclinic phase [ 36 , 45 , 46 , 47 ].…”

Role of a Solution-Processed V2O5 Hole Extracting Layer on the Performance of CuO-ZnO-Based Solar Cells

“…With band gaps of 1.34–1.7 eV and a high absorption coefficient, CuO, a p-type IMO, could be one of the promising candidates for photovoltaic applications. , CuO has some other excellent features like high minority carrier diffusion length, tunable electrical properties, etc. These features of CuO have enabled its use in the sensor, − photoelectrochemical cell, − capacitive device, − and photovoltaic ,− applications. According to the Shockley–Queisser limit, ∼30% power conversion efficiency (PCE) could be obtained from the single-junction CuO-based solar cells …”