Experimental and Computational Demonstration of In Situ Pt Nanocluster-Decorated ZnO Film for Ultra-Sensitive Hydrogen Detection

In this work, we present a Pt nanocluster-decorated ZnO thin film-based gas sensor for hydrogen detection, fabricated using the sputtering technique and in situ Pt decoration. The sensor exhibits a stable, highly sensitive, and repeatable response, making it a promising candidate for safety monitoring in hydrogen storage and transportation. Our sensor demonstrates optimal performance at an operating temperature of 225 °C with rapid response and recovery times (∼10 and 3 s), high selectivity, and long-term stability. We deposit the ZnO thin film on an interdigitated electrode (IDE) substrate, with Pt added to the (002) polar plane by brief sputtering (1 to 6 s) to create an active sensing interface. We find that the Pt nanocluster-decorated ZnO sensor, with a deposition time of 2 s exhibits an enhanced response (∼52,987%) to 1% hydrogen concentration, indicating its suitability for industrial applications. Our device demonstrates reliable detection of low hydrogen concentrations (∼100 ppb), with a response of ∼38% and no response drift over 1 year of testing, making it useful for environmental monitoring. To elucidate the role of Pt on ZnO for hydrogen sensing, we performed density functional theory calculations, analyzing adsorption and reaction energetics involving adsorbed H2, O2, O, OH, and H2O, as well as lattice oxygen atoms on the ZnO (002) surface with and without Pt decoration. Our computational data is in agreement with experimental observations, identifying the oxygen-exposed (002) surface to be the most active for hydrogen sensing in both pristine and Pt nanocluster-decorated ZnO. Further, our computations highlight the role of Pt in enhancing hydrogen sensitivity via i) activating the autoreduction pathway of adsorbed hydroxide species, ii) spontaneous dissociation of adsorbed molecular hydrogen, and iii) keeping the lattice oxygen pathway of forming water active. Our systematic approach of designing sensors, combining a robust experimental setup with theoretical insights, is key in developing efficient hydrogen sensors, as well as in understanding the mechanisms behind such superior performance.