Speaker
Description
Hydrogen (H2) fuel is emerging as one of the most viable green solutions in response to the rising global energy consumption. However, due to its high flammability, H2 can cause severe explosions in case of leakage [1]. Several H2 sensors have been developed, and palladium (Pd) based sensors have shown important optical and electrical properties, with the ability to dissociate catalytically the H2 molecule at its surface, by incorporating the resulting H atoms into its crystalline structure [1]. The use of nanostructure Pd–alumina metamaterials can highly improve the sensing properties, such as increased optical sensitivity to H2, improved sensor´s repeatability and durability, and can provide a route to tune the H2 absorption and desorption rates, that limit the H2 sensor response and recovery times [1,2]. Still, pure Pd based H2 sensors may inherently display non-linear behavior and large response times (on the order of minutes), while the use of PdAu alloys allows to suppress H2 absorption-desorption hysteretic behavior and decrease the sensing response times down to the order of seconds [3].
In this study, we review the fabrication of metamaterials for H2 optical sensing applications based on Pd/PdAu nanowires (NWs) and dendritic nanostructures grown inside nanoporous anodic aluminum oxide (AAO) templates by pulsed electrodeposition (Fig. 1). First, AAO templates were produced through an electrochemical anodization self-assembly process, where the controlled conditions allow tuning the diameters of the pores and result in hexagonal-close-packed arrays with dendritic nanostructured terminations [4]. The H2 optical response of homogeneous Pd NWs, in the order of 127 nm length and 49 nm diameter decreasing up to ~13 nm, as dendritic generations are formed, is reviewed [1]. To improve sensing performance, nanostructured PdAu alloys were fabricated, where the alloy composition was adjusted from 5.65-25.5 at.% Au by a simple change of the applied current density from 15-50 mA·cm-2 in the electrodeposition process. Future tests will include the use of the prepared PdAu-based metamaterials in a homemade optical fiber sensor device.
References
[1] P. Rodrigues et al., ChemistrySelect 1, 3854 (2016); A. Rodriguez et al., Nanotechnology 27, 185501 (2016).
[2] A. Guerreiro et al., Proc. SPIE 11207, 4th Int. Conf. on Appl. of Optics and Photonics, 1120724 (2019).
[3] C. Wadell et al., Nano Lett. 15, 5, 3563–3570 (2015).
[4] C. T. Sousa et al., Journal of Materials Chemistry 22, 3110 (2012).
