Supraparticles for naked-eye H2 indication and monitoring: Improving performance by variation of the catalyst nanoparticles

Abstract

The recent transition to H2-based energy storage demands for reliable H2 sensors that allow for easy, fast, and reliable detection of leaks. Conventional H2 detectors are based on the H2 probes of changes of physical properties induced by subsurface H-atoms to a material, such as electrical conductivity. Herein, we report on highly reactive gasochromic H2 detectors based on the adsorption of H2 on the material surface. We prepared supraparticles (SPs) containing different types of noble metal nanoparticles (NPs), silica NPs, and the dye resazurin by spray‑drying and tested their performance for H2 detection. The material undergoes a distinct color change due to the hydrogenation of the purple resazurin to pink resorufin and, finally, colorless hydroresorufin. The step-wise transition is fast and visible to the naked eye. To improve further the performance of the sensor, we tested the reactivity of SPs with different catalytically active NPs by means of in situ DRIFTS. We show that choice of the NP catalyst has a pronounced effect on the response of the H2 indicator. In addition, we demonstrate that the performance depends on the size of the NPs. These effects are attributed to the availability of reactive H‑atoms on the NP surface. Among the materials studied, Pt-containing SPs gave the best results for H2 detection.

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

“…We assign the peaks based on our previous work, which includes detailed density functional theory (DFT) calculations. , Here, the positive feature at ∼1460 cm –1 corresponds to ν­(C–N–C) (highlighted in red in Figure d) and the positive band at ∼1600 cm –1 to ν­(CO) (highlighted in orange in Figure d) of resorufin. In addition, the negative band at ∼1510 cm –1 is assigned to mixed ν­(N–H) + δ­(N–H) modes of hydroresorufin (highlighted in brown in Figure d).…”

“…More recently, we exploited the toolbox-like fabrication approach of the SPs via forced assembly in a spray-drying process to vary the catalyst NPs from Pd-based to Pt NPs at a constant molar concentration. 26 This systematic approach proved that SPs carrying Pt NPs perform superior in terms of reproducibility as compared to SPs with Pd-based NPs. We rationalize their characteristic performance by the differences in size (and thus their active specific surface area) and the metal (combination) of the incorporated catalyst NPs.…”

“…This ensures stable performance of the SP sensor before the evaluation of the detection limit. For details, we refer to Figure S2a in the SI and our previous work . The experimental procedure to evaluate the detection limit of the sensors includes a sequence of gas dosing cycles visualized in Figure S2b,d (SI).…”

“…Optical H 2 sensors stand out with their spark-free , and straightforward detection principle. In some cases, the optical response is even visible to the naked eye. − The vast majority of optical H 2 sensors utilize Pd as the functional material of choice. , Pd is not only able to efficiently dissociate H 2 gas at its surface but also absorbs the generated H species into interstitial sites of its metal lattice . Depending on the H 2 concentration, the reversible transformation toward the Pd-hydride phase yields a detectable optical contrast or reversible structural deformation accompanied by an altered optical transmittance. , …”

“…This yields a three-phase system consisting of solid SPs, liquid H 2 O, and H 2 gas. More recently, we exploited the toolbox-like fabrication approach of the SPs via forced assembly in a spray-drying process to vary the catalyst NPs from Pd-based to Pt NPs at a constant molar concentration . This systematic approach proved that SPs carrying Pt NPs perform superior in terms of reproducibility as compared to SPs with Pd-based NPs.…”