Atomic Surface Engineering of MXene for Stable Hydrogen Sensing at Low Temperature

MXenes have emerged as a promising class of two-dimensional (2D) materials for gas sensing applications, owing to their exceptional electrical conductivity, abundant surface functional groups, and tunable surface chemistry. However, the practical implementation of MXene-sensors is significantly hindered by the rapid oxidative degradation of their surface metallic atoms under ambient conditions. To address this challenge, an atomic-level surface engineering strategy is developed using atomic layer deposition (ALD) to integrate ZnO and Pd onto Ti₃C₂T_x MXene. The ZnO coating, selectively grown at hydroxyl-rich edges/surfaces, acts as a dual-functional layer: an ultra-effective oxidation barrier preserving MXene's conductivity while enabling charge transport. Concurrently, Pd nanoparticles serve as highly active catalytic sites for efficient H₂ dissociation and spillover. This synergistic design yields exceptional room-temperature hydrogen sensing performance. The optimized Pd-ZnO/MXene sensor achieves a rapid response/recovery (23 s/64 s to 50 ppm H₂), outperforming most reported MXene-based sensors. Density functional theory (DFT) confirms Pd's bifunctional catalytic role, drastically lowering energy barriers for both H₂ dissociation and O₂ adsorption/dissociation on ZnO-key to the low-temperature activity. This ALD-based approach establishes a universal platform for fabricating robust, high-stability MXene sensors, advancing their real-world deployment in hydrogen safety and clean energy applications.