Ultra-Wide ppb-to-ppm Dynamic Range for Room-Temperature Hydrogen Sensing via Obliquely Deposited Pd on Silicon Microcone Arrays

Abstract

Developing hydrogen (H2) sensors with ultralow detection limits, high response, and room-temperature operation is critical for the safe utilization of H2 energy. Herein, we report a highly sensitive H2 sensor based on palladium nanoparticle (Pd NP)-decorated silicon microcone (Si MC) arrays, with a systematic investigation of metal deposition conditions. Large-area, uniform, and smooth Si MC arrays were fabricated via metal-assisted chemical etching (MACE). The Pd deposition angle (0−90°) plays a vital role in sensing performance. The optimized 3 Pd-75° sensor (3 nm Pd, 75° deposition) exhibits an exceptional response of 2148.9% toward 10,000 ppm H2 at room temperature, along with fast recovery (∼4 s), good humidity tolerance, long-term stability, and excellent selectivity. Notably, it achieves an ultrawide quantitative detection range from 10 ppb to 2000 ppm. Furthermore, Pt modification reveals a trade-off between catalytic activity and electrical response: while Pt accelerates H2 dissociation and diffusion, it reduces response magnitude due to active site blocking and enhanced conduction pathways. The superior sensing performance arises from the synergistic effects of Pd catalysis, Pd/Si interfacial charge modulation, and the high surface area of the Si MC architecture. This work provides a promising strategy for low-power, high-performance room-temperature H2 sensing.