Molecular and Structural Insights into H₂ Indicator Supraparticles: Lowering the Limit of Detection by Tuning Incorporated Catalyst Nanoparticles

With the increasing interest in H 2 -based energy storage, H 2 detectors gain significant importance. Here, we report on safe, i.e., spark-free, reliable, and highly reactive gasochromic H 2 indicator supraparticles (SPs). They are assembled from different types of noble metal nanoparticles (NPs), SiO 2 NPs, and the dye resazurin via spray-drying. Their sensing principle is based on the adsorption and activation of H 2 on catalytically active noble metal NPs incorporated in the mesoporous supraparticulate framework. Upon stepwise hydrogenation of resazurin molecules with molecular mobility via activated H species, the indicator displays a fast color change visible to the naked eye. We investigate the effect of incorporating different catalytically active NPs into indicator SPs on their sensor performance at different H 2 concentrations. We find that the size and material of the catalyst NPs have a strong influence on the sensor response of the H 2 indicator as it changes the amount of activated H species available in the system. Enhancing the amount of interstitial H 2 O in the mesopores of the SPs increases their reaction volume but impairs the reproducibility of their sensor response. Among the studied materials, dispersed Pt NP-containing SPs give the overall best results in terms of overall performance toward H 2 detection.