Robust Hydrogen-in-Oxygen Sensing in Alkaline Water Electrolysis via Hydrophobic MoS₂ Interface Engineering

Alkaline water electrolysis (ALK) is a promising route for large-scale green hydrogen production, but hydrogen-oxygen mixing during operation poses severe explosion risks, requiring reliable hydrogen-in-oxygen monitoring. Existing sensors suffer from degraded performance under ALK conditions (80-95 °C, 30% KOH) due to water-hydrogen competitive adsorption and alkali corrosion. Here, we report a hydrophobic MoS₂-based semiconductor hydrogen sensor engineered via surface grafting of cetyltrimethylammonium bromide molecules. The resulting protective layer prevents alkali penetration while preserving rapid hydrogen adsorption/desorption. The sensor achieves detection over 0.001-2.5% H₂ with a 3 s response and 50 s recovery and maintains <4.2% sensitivity fluctuation during 10 h operation in simulated harsh environments. This work provides a robust sensing strategy for hydrogen safety monitoring in extreme alkaline electrolysis, with broad implications for safe hydrogen energy deployment.