Sub-2 nm Pt Clusters Boost Lattice Oxygen Activation in Ultrathin In2O3 Nanosheets for Ultrafast and Wide-Range Hydrogen Sensing

The safe deployment of hydrogen (H₂) as a clean fuel requires portable sensors capable of rapid, sensitive, and reliable H₂ detection over a wide concentration range. Loading noble metals on metal oxide semiconductors (MOS) is a promising route for enhance H₂ sensing; however, achieving high atomic utilization at low noble metal loading while simultaneously improving sensitivity remains challenging. Herein, sub-2 nm Pt clusters (<2 nm) loading on ultrathin In₂O₃ nanosheet-aggregated hierarchical structures (Pt_sub-In₂O₃) are successfully prepared. The Pt_sub-In₂O₃-based sensor demonstrates an ultrafast response time of ∼1 s and a recovery time of ∼4 s, along with an exceptionally wide detection range spanning six orders of magnitude (0.2 ppm to 2% H₂), excellent selectivity, and outstanding long-term stability. Mechanistic investigations using H₂-TPR, X-ray absorption spectroscopy, and density functional theory calculations reveal that the sub-nanometer Pt clusters not only facilitate hydrogen spillover but also effectively activate the surface lattice oxygen of In₂O₃, which collectively account for the drastically enhanced sensing performance. This work demonstrates that atomic-scale engineering of noble metal clusters offers a viable pathway toward high-performance, practical gas sensors.