Comparative study on CO2 and CO sensing performance of LaOCl-coated ZnO nanowires

Carbon dioxide (CO2) and carbon monoxide (CO) emissions from industries and combustion fuels such as coal, oil, hydrocarbon, and natural gases are increasing, thus causing environmental pollution and climate change. The selective detection of CO2 and CO gases is important for environmental monitoring and industrial safety applications. In this work, LaOCl-coated ZnO nanowires (NWs) sensors are fabricated and characterized for the detection of CO2 (250-4000 ppm) and CO (10-200 ppm) gases at different operating temperatures. The effects of the LaCl3 coating concentration and calcination temperature of the sensors are studied. They are found to have a strong influence on the sensing performance to CO2 gas, but a relatively slight influence on that to CO. The LaOCl coating enhances the response and shortens the response and recovery times to CO2 compared with those to CO. The enhanced response of the LaOClcoated ZnO NW sensors is attributed to the extension of the electron depletion layer due to the formation of p-LaOCl/n-ZnO junctions on the surfaces of the ZnO NWs. (C) 2012 Elsevier B.V. All rights reserved.