Electron-Deficient Pd Enabled by Single-Atom Alloy Drives Fast and CO-Resistant Hydrogen Sensing

Pd-based nanoparticles have been widely employed to enhance H 2 sensing performance due to their strong capability for H 2 adsorption and dissociation. However, strong Pd–H* interactions hinder the hydrogen spillover process, while pronounced CO adsorption results in poor selectivity. Herein, we propose a Pt–Pd single-atom alloy (SAA) sensitization strategy that creates electron-deficient Pd δ+ sites to modulate the interaction between Pd and gas molecules. As a proof of concept, Pt 1 Pd SAA is deposited on commercial SnO 2 to fabricate H 2 sensors. The resulting device achieves an ultra-low detection limit (21 ppb), short response and recovery time (0.8 s and 5.9 s), excellent selectivity and enhanced CO resistance, outperforming traditional Pd nanoparticles, PtPd alloy sensitizers modified SnO 2 gas sensors, and commercial H 2 sensors. Mechanistic studies establish that atomic Pt induces electron-deficient Pd δ+ sites, achieving atomic-scale decoupling of hydrogen activation from CO adsorption, which enables barrierless hydrogen spillover and inherently CO-resistance H 2 sensing, with CO back-donation suppressed by nearly 50%. This study presents a robust SAA sensitization strategy that leverages atomic-level modification-induced electronic structure modulation to overcome the sensitivity-selectivity trade-off, demonstrating its promise for next-generation H 2 sensors.