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

Abstract

With the increasing interest in H2-based energy storage, H2 detectors gain significant importance. Here, we report on safe, i.e., spark-free, reliable, and highly reactive gasochromic H2 indicator supraparticles (SPs). They are assembled from different types of noble metal nanoparticles (NPs), SiO2 NPs, and the dye resazurin via spray-drying. Their sensing principle is based on the adsorption and activation of H2 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 H2 concentrations. We find that the size and material of the catalyst NPs have a strong influence on the sensor response of the H2 indicator as it changes the amount of activated H species available in the system. Enhancing the amount of interstitial H2O 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 H2 detection.

Mesoporous supraparticles with a tailored solid–liquid–gas interface for visual indication of H2 gas and NH3 vapours

“…13 SPs are hierarchical assemblies of nanoparticle (NP) building blocks with a consistent structural motif, 14 offering a highly customizable material design. 13,[15][16][17] The established gasochromic SPs exploit (ir)reversible colour changes of incorporated Reichardt's betaine dye or resazurin (RES) for the detection of NH 3 vapours 13 and H 2 gas, [15][16][17][18] respectively. However, the NH 3 -indicator SPs cannot detect H 2 , and vice versa.…”

“…For a proof-of-concept study, we exemplary used RES as an indicator dye as it is well studied by others 11 and us. [15][16][17][18] We focused in our study on how the addition of H 2 SO 4 to the mixed dispersion prior to spray-drying influences the morphology, structure, texture and functionality of the resulting SPs. The mixed dispersion of the reference SP system containing SiO 2 NPs, Pt NPs and RES had a pH E 10 due to the NaOHstabilisation of the SiO 2 NP dispersion.…”

“…Both types of SPs show a spherical or doughnutlike morphology and a size distribution ranging from E2 to E8 mm. As the Pt NPs are essential for the detection of H 2 , 16 we studied their distribution within the SP framework via SEM imaging of SP cross-sections using back-scattered electron detecting to obtain elemental contrast. Without the addition of H 2 SO 4 , the Pt NPs are well dispersed throughout the entire SP (Fig.…”

“…2A1, after ex situ H 2 O dosing). [15][16][17] First exposure to H 2 leads to the irreversible reduction of deprotonated RES (purple) to deprotonated resorufin (RF, pink), followed by a reversible reduction to hydroresorufin (hRF, colourless) upon further H 2 dosing (Fig. 2A2).…”