(696b) N-Type Conducting Polymers as New Materials for Ultrasensitive Hydrogen Detection

Hydrogen is a promising next-generation fuel source due to its high energy density, natural abundance, and clean combustion. However, its high flammability and permeability raise significant risks for its use in transportation. Thus, highly sensitive sensors that can detect leaks well before they pose an explosion risk are crucial to safely deploying this technology. Chemiresistive sensors are the simplest and most commercially developed devices but have trouble achieving the desired goal of parts per billion detection at room temperature. These devices generally consist of two components: an active metal layer (usually Pd) that reversibly reacts with hydrogen to form PdHx phases, and a semiconductor that is doped or dedoped during this transition to trigger a large conductivity change.

These limitations are largely due to the semiconductor layer. Metal oxide semiconductors (MOS) are the industry standard due to their large signal amplification and low limits of detection. However, their sluggish kinetics and high humidity sensitivity require operation at high temperatures, leading to high energy consumption and potential ignition risk. In contrast, carbon nanomaterials function at room temperature in humid conditions, but generally exhibit lower sensitivity.

To address these deficiencies, we introduce n-type conducting polymers as a new scaffold for hydrogen sensing that combines the benefits of both material classes. Their high electron affinity and large change in conductivity upon doping imparts the high sensitivity of MOS devices, while the organic, relatively hydrophobic backbone enhances humidity tolerance. To achieve rapid kinetics at room temperature, we develop a new layered device architecture, where the polymer sits between an electron rich Pd/Pt layer and an electron deficient vanadium oxide layer. By decoupling the doping and de-doping processes to two spatially separated metal layers, we achieve parts per billion limits of detection at room temperature in wet and dry air. By leveraging this new material and device configuration, we realize state-of-the-art hydrogen sensing via fabrication methods that are cheap, simple, and commercially viable.