PdAu Alloy Nanoparticles for Hydrogen Sensing

Abstract

The potential of a hydrogen economy introduces the need for efficient hydrogen storage as well as reliable gas sensors. Hydride-forming metal particles may be the solution to both these problems. In this thesis we present a means of fabrication of PdAu alloy nanoparticles, suitable for LSPR sensing of hydrogen gas concentrations. Heterogeneous particles of stacked Pd+Au layers were fabricated using Hole-Mask Colloidal Lithography. The particles were annealed at different temperatures in order to promote alloying. Full alloying seems to be achieved at 500 C, as was confirmed by XPS measurements and by hydrogen uptake characteristics. Hydrogen ab-/desorption cycles were measured by monitoring the LSPR spectra of the particles while varying the hydrogen pressure. The hysteresis of the a-b transition decreased with increasing gold content, in agreement with measurements on thin films. The hydrogen ab-/desorption kinetics were faster for PdAu than for pure Pd particles and the rate limiting steps seem to be different. Addition of Au may improve optical hydrogen sensors based on Pd. Nanoparticles may prove beneficial over thin films due to the possibility of LSPR sensing and faster kinetics due to shorter diffusion.