Pd-Ti Alloy Thin Films for Fast and Sensitive Hydrogen Detection using the Near-Infrared Readouts

High-performance and cost-effective hydrogen sensors are essential for the safe management of hydrogen in carbon-free energy systems, given its broad flammability range in air. Among various sensor technologies, optical sensors are favored for their enhanced safety characteristics. Most hydrogen sensors with low detection limits (LOD) have been explored in the visible range. While pure palladium (Pd) and titanium (Ti) metals exhibit strong sensitivity in the near-infrared (NIR) region, neither material alone is ideal for hydrogen sensing due to limitations like slow response times and non-specific signals. In this study, we systematically investigate the optical properties and hydrogen-sensing performances of Pd-Ti alloy thin films and nano-patchy arrays, considering various alloy stoichiometries and thicknesses across a wide spectral range (400-1650 nm). The polymer-coated Pd-Ti sensor achieves a response time (t₉₀) close to 1 second at 1000 ppm H₂ throughout the entire spectrum with significantly improved sensitivity at longer wavelengths, reaching a part-per-million LOD. These findings are further validated using Effective Medium Theory and Finite-Difference Time-Domain (FDTD) simulations, underscoring the potential of Pd-Ti alloys as high-performance, spark-free optical sensors for precise hydrogen quantification.