Active and passive electrode matrix optimization technique to improve humidity sensing performance of MoS2-based devices: unfolding an innovative avenue

Abstract

Active electrodes” that are primarily used for the collection of carriers and “passive electrodes” that actively take part in target gas molecule dissociation (gas-induced carrier generation but not collection), owing to their catalytic nature, were judiciously coupled and optimized in a matrix for the first time with an aim to enhance humidity sensing performance of the MoS2-based devices. Intrigued by the design concept of electroencephalogram (EEG) electrode configurations, the present endeavor uniquely adapted the electrode matrix for gas-sensing scenarios. MoS2 nanoflowers were synthesized through hydrothermal deposition, while Pd electrodes, which were used both as active and passive ones, were deposited by electron beam evaporation using a suitably designed metal shadow mask. The innovation of this study lies in the strategic incorporation of catalytic Pd-based electrodes (both as active and passive), where two active electrodes ( 2×2 mm) facilitated signal transmission to the measurement unit, while multiple passive electrodes ( 0.5×0.5 mm) enabled carrier generation through catalytic dissociation of the target gas. The optimum number of passive electrodes was identified to be six offering the highest response magnitude (RM). The optimized sensor was tested across a relative humidity (RH) range of 8%–84%, demonstrating an RM of 54.4% at 84% RH. To provide deeper insight into the sensing mechanism, a theoretical model was developed to quantitatively correlate the RM with RH levels. Comparison with the existing resistive humidity sensors demonstrated the superior performance of the developed sensor, making it a strong candidate for applications in industrial humidity control, healthcare, smart IoT systems, and environmental monitoring.