Structure of a single palladium nanoparticle and its dynamics during the hydride phase transformation

Abstract

Palladium absorbs large volumetric quantities of hydrogen at room temperature and ambient pressure, making the Pd-H system a promising candidate for hydrogen storage. Here, we use Bragg coherent diffraction imaging to map the strain associated with defects in three dimensions before and during the hydride phase transformation of an individual octahedral palladium nanoparticle, synthesized by using the seed-mediated approach. The displacement distribution imaging unveils the location of the seed nanoparticle in the final nanocrystal. By comparing our experimental results with a finite-element model, we verify that the seed nanoparticle causes a characteristic displacement distribution of the larger nanocrystal. During the hydrogen exposure, the hydride phase is predominantly formed on one tip of the octahedra, where there is a high number of lower coordinated Pd atoms. Our experimental and theoretical results provide an unambiguous method for future structure optimization of seed-mediated nanoparticles growth and in the design of palladium-based hydrogen storage systems.

Applications of Neutron Scattering in Technical Catalysis: Characterisation of Hydrogenous Species on/in Unsupported and Supported Palladium

“…-Differences found in hydrogen absorption studies [9,[27][28][29][30] for larger and isolated small Pd particles with different average primary particle size -Differences in the width and position of the α-/β-phase transition region [27][28][29][30] due to varying long-range phase coherence, the latter being of relevance for the hydride phase transition [31,32] -Results from computational studies on long-range attractive forces and short-range repulsive forces and the phase stability in palladium hydrides [33] Results and discussion Fig. 2, top and Fig.…”