Pd-Coated Porous Silicon Microcones for High-Performance Hydrogen Sensing at Room Temperature.

The rational design of sensing materials is pivotal for enhancing gas detection capabilities, especially for hydrogen (H), a clean yet highly flammable energy carrier. Despite extensive efforts, achieving reliable and sensitive H detection under ambient conditions remains a significant challenge. Here, we present a highly sensitive room-temperature H sensor based on palladium (Pd)-decorated porous silicon (Si) microcone arrays. The porous microcones were fabricated via photolithography and metal-assisted chemical etching, followed by Pd deposition using angle-controlled electron beam evaporation. By systematically tuning the Pd thickness and deposition angle, the sensor achieved an optimal response of 347% to 10,000 ppm of H and a detection limit of 1 ppm at room temperature. The porous Si microcone structure offers a large surface area and efficient gas diffusion pathways, while oblique-angle Pd deposition enhances catalytic activity and facilitates interfacial modulation. The sensor also exhibits a broad dynamic detection range (0.0001-2%), excellent selectivity, and long-term stability. Furthermore, codecoration with Ag, Au, or Pt enables further tuning of response and recovery times. The demonstrated compatibility with Si-based processes underscores its potential for integration into next-generation low-power H monitoring systems.