Safety Through Visibility: Tracing Hydrogen in Colors with Highly Customizable and Flexibly Applicable Supraparticle Additives

Abstract The flammability of H ₂ ‐air mixtures demands timely detection and precise localization of H ₂ leakages to ensure safety and targeted maintenance measures in the anticipated hydrogen economy. Herein, H ₂ indicator supraparticles (SPs) are demonstrated that meet this demand by making H ₂ visible to the naked eye by a rapid (ir)reversible color change. Their toolbox‐like manufacturing from SiO ₂ nanoparticles (NPs), Pt NPs, and indicator dye molecules via spray‐drying allows for engineering their structure, texture, and detection performance by systematically tuning their composition. It is demonstrated that decreasing the SiO ₂ NP size, increasing the Pt NP concentration, and adjusting the amount of dye molecules improve the SPs’ response times. This opens up the option for multidimensional customization of their detection performance. Furthermore, the toolbox of H ₂ indicator SPs containing the established resazurin system is expanded to other indicator dyes, which makes a color change and reversibility of choice feasible. H ₂ indicator SPs meet many of the target characteristics for H ₂ detectors, e.g., low limit of detection, cycle stability, and high selectivity. Moreover, the SPs’ particulate nature allows for their flexible application as an additive, e.g., in coatings or clothing, which enables the detection and localization of H ₂ leakages in relevant application scenarios.