Two-Dimensional Hybrid SnO2@WO3 Nanosheets Synthesized by Polyoxometallate Cluster-Nucleus Coassembly for Highly Efficient H2 Detection.

Hydrogen's extreme flammability and propensity for undetected leaks pose critical safety hazards in renewable energy and industrial systems, yet noble-metal-free sensors face intrinsic limitations in response kinetics and stability. Herein, we report a noble-metal-free hydrogen-sensitive SnO2@WO3 hexagonal nanosheets synthesized via a cluster-nucleus coassembly strategy. The bottom-up coassembly approach directs the interfacial self-assembly of WO3 clusters and SnO2 nuclei, enabling atomic-level coupling at the heterointerface. The SnO2@WO3 heterointerface modulates the W coordination environment, amplifying oxygen vacancy (Ov) density compared to that of pristine SnO2. Remarkably, the sensor based on SnO2@WO3 exhibited unique H2 gas sensing properties in the absence of catalytic sensitization of noble metals, including a high response value (Ra/Rg = 12.06 for 1000 ppm of H2), rapid response time (8 s), excellent selectivity, and long-term stability and durability. The synergy of the two-dimensional nanosheet morphology and interfacial Ov-rich heterojunction facilitates efficient gas diffusion, charge transfer, and dissociation. The H2 adsorption (-1.367 eV) and O2 dissociation (-0.767 eV) at interfacial Ov sites explain the performance enhancement. Furthermore, we present a fully integrated wireless sensor module for real-time H2 monitoring with smartphone visualization via Bluetooth. In addition, we also demonstrated how a sensor-integrated smart car can dynamically inspect hydrogen leaks. This work introduces a new paradigm for designing high-performance tunable heterostructures for next-generation gas detection.