Highly Sensitive Room-Temperature Hydrogen Detection with Palladium Nanoparticle-Based Capacitive-Type Sensors

Palladium nanoparticle (Pd NP)-based resistive-type hydrogen (H₂) sensors are susceptible to interference from oxygen when detecting H₂. In contrast, capacitive-type sensors emerge as promising candidates for addressing this issue, owing to their unique operating principle. Herein, a capacitive-type H₂ sensor is developed to verify the conception, using Pd NPs as the sensing material and integrating them into a novel 3D interdigital electrode (IDE) structure fabricated on a silicon wafer via microelectromechanical systems (MEMS) technology. Comprehensive characterization of the Pd NPs within the 3D IDEs reveals a strong correlation between sensitivity and Pd NP content, with peak sensitivity (61.94) attained at 20 000 ppm H₂ for ≈0.7 mg of Pd NPs. The sensor demonstrated negligible interference from CH₄, CO₂, and CO, underscoring its exceptional selectivity for H₂. Particularly, variation of oxygen concentration in the background gas shows a minor impact on the sensing performance of the developed capacitive H₂ sensor. Additionally, density functional theory (DFT) calculations provide insight into the volumetric expansion of Pd at different H/Pd ratios, showing a maximum expansion of 13.7% at an H/Pd ratio of 1. This work highlights the potential of capacitive-type sensors for high-performance tracking H₂, paving the way for advanced applications in H₂ monitoring.