Grain-growth mediated hydrogen sorption kinetics and compensation effect in single Pd nanoparticles

Svetlana Alekseeva,Vladimir P Zhdanov,Sara Nilsson,Michal Strach,Christoph Langhammer,Joachim Fritzsche

doi:10.1038/s41467-021-25660-x

Svetlana Alekseeva, Vladimir P Zhdanov + Show 4 more

Open Access

https://doi.org/10.1038/s41467-021-25660-x

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Abstract

Grains constitute the building blocks of polycrystalline materials and their boundaries determine bulk physical properties like electrical conductivity, diffusivity and ductility. However, the structure and evolution of grains in nanostructured materials and the role of grain boundaries in reaction or phase transformation kinetics are poorly understood, despite likely importance in catalysis, batteries and hydrogen energy technology applications. Here we report an investigation of the kinetics of (de)hydriding phase transformations in individual Pd nanoparticles. We find dramatic evolution of single particle grain morphology upon cyclic exposure to hydrogen, which we identify as the reason for the observed rapidly slowing sorption kinetics, and as the origin of the observed kinetic compensation effect. These results shed light on the impact of grain growth on kinetic processes occurring inside nanoparticles, and provide mechanistic insight in the observed kinetic compensation effect.

Highlights

Grains constitute the building blocks of polycrystalline materials and their boundaries determine bulk physical properties like electrical conductivity, diffusivity and ductility
The understanding of the influence of grain boundaries on kinetic processes, for example during nanoscale phase transformations, is widely lacking. This is problematic since phase transformations in nanostructured materials are a central concept in energy storage technologies like batteries[15,16] and hydrides[17], in hydrogen sensors[18,19], as well as in heterogeneous catalysis, for example in situations with metal catalyst oxidation[20,21,22]. To overcome this current lack of understanding, single particle experiments hold the key since they have been successfully deployed to investigate the impact of nanostructure dimensions and geometry on the thermodynamics of phase transformation processes, where they have focused on hysteresis effects[7,8,11] and the role of defects like dislocations and voids[9,10,12]
In this work that fills this gap, we investigate the kinetics of the hydride formation and decomposition in individual polycrystalline Pd nanoparticles due to their importance for hydrogen storage[17], hydrogen sensors[2] and as model system for other solute-induced phase transformations in nanomaterials, and we reveal the evolution of grain morphology induced by this firstorder phase transformation

Summary

Introduction

Grains constitute the building blocks of polycrystalline materials and their boundaries determine bulk physical properties like electrical conductivity, diffusivity and ductility. To further corroborate the GIXRD results, we performed TEM characterization of the same single nanoparticle before cycling, and after 12 and 30 (de) hydrogenation cycles, respectively, which confirms the significant hydrogen sorption-induced grain growth (Fig. 3c).

Results

Conclusion