Room temperature operated hydrogen sensor using palladium coated on tapered optical fiber

Abstract

Gaseous pollutants such as hydrogen gas (H2) are present in daily human activities and have been studied extensively due to their high explosive and widespread use in many fields. A common H2 gas detector is electrically based. Although these electrical or conductometric sensors attain high sensitivity, they suffer from drawbacks, including poor selectivity, high operating temperature, and susceptibility to electromagnetic interference, which the optical-based sensor can improve. This study describes the development of a palladium-coated (Pd) optical fiber for the room temperature (H2) hydrogen application process. To improve the evanescent light field that propagates through the fiber, a multimode fiber was used to fabricate a transducing channel with cladding and core diameters of 125 μm and 62.5 μm respectively. The multimode optical fibers were tapered from 125 μm cladding diameters to 20 μm diameter, 10 mm waist-length, 5 mm to the up and down tapered region, and coated with Pd by using the drop-casting technique. Various characterization techniques have been used to characterize palladium, such as Field Emission Scanning Electron Microscopy (FESEM), X-ray energy scattering (EDX), X-ray Diffraction (XRD), and atomic force microscopy (AFM). The fabricated Pd-based sensor operates safely at room temperature with a gas concentration of 0.125 % to 2.00 % H2. The measured sensitivity, response, and recovery time were 18,645 %, 50 s, and 230 s, respectively. The selectivity of the fabricated sensor toward H2 was affirmed with no response to other gases such as ammonia (NH3) and methane (CH4). However, this study demonstrates reliable, efficient, and reproducible H2 detection using a simple and cost-effective method.