Effect of ‘Pt’ loading in ZnO–CuO hetero-junction material sensing carbon monoxide at room temperature

Sensing of carbon monoxide (CO) was carried out with ZnO–CuO and Pt/ZnO–CuO. Synthesized materials were characterized by temperature-programmed reduction (TPR), high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The composite materials of ZnO–CuO were found to have an active sensing center, The sensor response obtained for an optimized ratio of ZnO and CuO (1:1 weight ratio) yielded the highest response of 1.28 (Rco/Rair) for 1000 ppm of CO at room temperature; the response and recovery times were found to be 41 and 86 s, respectively. However, loading 1:1 ZnO–CuO with 0.4% Pt boosted the sensor response to 2.64 (Rco/Rair) for the same CO concentration. The sensor (0.4% Pt/ZnO–CuO) response was linear towards CO concentrations between 100 and 1000 ppm. In the Pt loaded case both the response and recovery times were found to be 81 s. A mechanism for CO sensor response was put forward with reference to CO adsorption and desorption.