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 (Ptsub-In2O3) are successfully prepared. The Ptsub-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.