[Abstract]

Hydrogen is a promising clean energy carrier. However, because of its high flammability, fast and reliable detection is required, particularly near the explosive threshold of 4% in air. Herein, we present a highperformance and reliable hydrogen sensor based on polymer-wrapped semiconducting single-walled carbon nanotubes (sc-SWCNTs) decorated with thermally evaporated Pd nanoparticles. The sc-SWCNTs not only serve as a charge transport channel but also govern the spatial distribution of Pd, enabling an effective catalytic interface. This sensor exhibits stable, concentration-dependent responses across 1–20% hydrogen concentrations, with sensitivities of 881 and 876 to 4% hydrogen in two consecutive 10-min exposure cycles, along with a rapid response of approximately 1 s and excellent stability under repeated exposure. A clear response is further obtained at 10 ppm H2, highlighting its extended detection range. In wafer-scale fabrication, 156 sensors were fabricated in a single process on a 6-inch substrate, demonstrating high uniformity consistent with the singledevice results, with an average sensitivity of 645.29 ± 4.58. The systematic modulation of SWCNT density and Pd thickness reveals a critical transition in charge transport from SWCNT-based sensing to metallic Pd percolation. This study proposes a reliable hydrogen sensor that can be manufactured over a large area through a cost-effective process, enabling safety monitoring across a broad hydrogen concentration range.