Interfacial Hydrogen Spillover on Au/Mn‑In2O3 with Oxygen Vacancies Boosts Hydrogen Sensing with Ultrafast Response

Accurate and rapid hydrogen (H2) sensing is critical for safety monitoring in hydrogen energy and industrial leak detection. However, achieving both high sensitivity and fast response in semiconductor oxide-based H2 sensors at low temperatures remains challenging. Herein, we report Au/Mn‑In2O3 support with oxygen vacancies to promote efficient hydrogen spillover by reducing the work function difference between Au and the oxide support. This lowers the kinetic barrier for H migration across the metal-support interface, as confirmed by density functional theory calculations. The in situ spectra characterization further confirmed the enhanced hydrogen migration over the Au/Mn-In2O3. An ultrafast response (1 s to 500 ppm H2) and a low detection limit of 12.5 ppb were achieved at 280 °C. More importantly, the optimized sensor delivered accelerated response/recovery kinetics at low temperature (8 s/19 s, 150 °C). The oxygen vacancies also provide efficient spillover pathways and moderately downshift the d‑band center of Au, collectively accelerating hydrogen desorption and completing the sensing cycle. This work highlights work function engineering as a viable strategy to overcome the spillover bottleneck in noble‑metal/oxide gas sensors.