Balancing Pd-H Interactions: Thiolate-Protected Palladium Nanoclusters for Robust and Rapid Hydrogen Gas Sensing

The transition toward hydrogen gas (H₂) as an eco-friendly and renewable energy source necessitates advanced safety technologies, particularly robust sensors for H₂ leak detection and concentration monitoring. Although palladium (Pd)-based materials are preferred for their strong H₂ affinity, intense palladium-hydrogen (Pd-H) interactions lead to phase transitions to palladium hydride (PdH_x), compromising sensors' durability and detection speeds after multiple uses. In response, this study introduces a high-performance H₂ sensor designed from thiolate-protected Pd nanoclusters (Pd₈SR₁₆), which leverages the synergistic effect between the metal and protective ligands to form an intermediate palladium-hydrogen-sulfur (Pd-H-S) state during H₂ adsorption. Striking a balance, it preserves Pd-H binding affinity while preventing excessive interaction, thus lowering the energy required for H₂ desorption. The dynamic adsorption-dissociation-recombination-desorption process is efficiently and highly reversible with Pd₈SR₁₆, ensuring robust and rapid H₂ sensing at parts per million (ppm). The Pd₈SR₁₆-based sensor demonstrates exceptional stability (50 cycles; 0.11% standard deviation in response), prompt response/recovery (t₉₀ = 0.95 s/6 s), low limit of detection (LoD, 1 ppm), and ambient temperature operability, ranking it among the most sensitive Pd-based H₂ sensors. Furthermore, a multifunctional prototype demonstrates the practicality of real-world gas sensing using ligand-protected metal nanoclusters.