Morphology-Dependent Chemiresistive-Potentiometric Gas Sensing Properties of ZnO Nanorods for CH₄ and CO

In this study, one-dimensional ZnO nanorods sensing electrodes were grown in situ on the surface of the Ce 0.8 Gd 0.2 O 1.9 electrolyte to fabricate chemiresistive-potentiometric (C-P) bivariate sensors for the detection and identification of CH 4 and CO. Four C-P sensors were developed by adjusting the hydrothermal growth time of the nanorods. The effect of hydrothermal duration on the morphology of nanorods was examined. The C-P response to CH 4 and CO initially increased and then decreased with increasing hydrothermal duration. Similar variations in the response to the gas mixtures of CH 4 and CO with the hydrothermal duration were observed. The highest C and P response values for CH 4 , CO, and their mixtures were obtained at a hydrothermal duration of 1.5 h. The enhanced C-P sensing performance was discussed in terms of the defect density, the number of contact junctions, and the length of ZnO nanorods. Accurate differentiation of five different gases (CH 4 , CO, and three gas mixtures) with an identification accuracy of 100% was achieved by the array assembled with the ZnO-1.0 and the ZnO-1.5 sensors. Our findings demonstrate the morphology-dependent C-P sensing behaviors of ZnO nanorods and provide a facile and cost-effective method for the detection and identification of CH 4 and CO.