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

Abstract In this study, one-dimensional ZnO nanorods sensing electrodes were grown in situ on the surface of the Ce₀.₈Gd₀.₂O₁.₉ electrolyte to fabricate chemiresistive-potentiometric (C-P) bivariate sensors for the detection and identification of CH4 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 CH4 and CO initially increased and then decreased with increasing hydrothermal duration. Similar variations in the response to the gas mixtures of CH4 and CO with the hydrothermal duration were observed. The highest C and P response values for CH4, 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 (CH4, 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 CH4 and CO.