Microwave Gas Sensor Based on Differential Planar Resonator Synergistically Loaded With Pd-Doped CdSnO₃ for Enhanced H₂S Detection

In this letter, a microwave gas sensor (MGS) is proposed for detecting H2S, based on a differential complementary split ring resonator (DCSRR) with Pd-doped CdSnO3 (Pd-CdSnO3) loaded in the region confining a strong electric field (E-field). Pd-CdSnO3 converts changes of H2S concentration into variations in electrical properties, synergizing with the strong E-field of DCSRR and reflected in the alterations of the reflection coefficient. Benefiting from the spill-over effect and superior catalytic activity of the employed Pd for H2S, as well as the synergism of Pd-CdSnO3 and DCSRR, the proposed MGS exhibits excellent sensing performance. At room temperature, the proposed MGS achieves a high sensitivity of 0.49 dB/ppm for low (1 ppb-0.2 ppm) and 0.21 dB/ppm for high (0.5-50 ppm) concentrations of H2S. In addition, the proposed MGS exhibits a low experimental detection limit of 1 ppb and high selectivity.