Pd- and Pt-based nanomaterials for hydrogen sensing in complex environments: the role of composition, morphology and defects

Doctoral thesis, 2026

In many technological applications of hydrogen gas (H₂), H₂ interacts with different forms of metals. H₂ sensors are one example, where irrespective of the sensing principle, Pd, Pt and their alloys often constitute the active sensing material. While reasonably well characterized for bulk systems, e.g. macroscopic films, the interaction of H₂ with nanoparticle alloys, which in this thesis generally are in the form of disks with a diameter of 100 nm, remains a widely uncharted territory. Especially in chemically complex environments that include species like O₂, H₂O, CO and NO_X.

In this thesis, the hydrogen sorption characteristics and morphological evolution of neat Pd, Pt, and more than 70 alloy combinations of the two, both at the single nanoparticle and at the ensemble level are investigated. To do so, we have developed a new nanolithography fabrication method, that is combined with plasmonic nanospectroscopy, dark-field nanomicroscopy and electron microscopy and spectroscopy.

First, we find a strong intrinsic link between the evolution of hydrogen sorption kinetics and single-particle specific defect networks. Secondly, we quantify how a few atomic percent of secondary alloyants can stabilize the structure of these particles during heavy H₂ cycling and consequently also stabilize the time evolution of hydrogen sorption kinetics. This is important in H₂ sensor applications because it paves the way to sensors which deliver a stable response over extended operation. We also demonstrate how systematic alloy composition screening of Pd- and Pt-based alloy and hybrid nanoparticles,  together with advanced deep learning-based data analyzation, can be leveraged to achieve plasmonic H₂ sensors that operate efficiently in technologically relevant, but highly challenging, environments, i.e., air with high levels of O₂, CO, NO_x and varying relative humidities.