Probing Strain in Individual Palladium Nanocrystals during Electrochemically Induced Phase Transitions

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• The palladium-hydrogen system is vital for catalysis, hydrogen storage, and sensing.
• Understanding phase transitions in palladium nanocrystals (NCs) is key to hydrogen absorption/desorption.
• Hydrogen trapping and embrittlement are critical phenomena influenced by these phase changes.

Purpose of the Study:

• To investigate the strain and lattice parameter evolution during the α-to-β phase transition in palladium NCs.
• To elucidate the mechanisms governing hydrogen absorption and desorption in palladium.
• To develop a comprehensive model for the palladium phase transition.

Main Methods:

• In situ Bragg coherent diffraction imaging under electrochemical control.
• Minimization of X-ray beam effects for accurate measurements.
• Strain and reciprocal space analysis combined with molecular simulations.

Main Results:

• Lattice parameter changes in both α and β phases were successfully tracked.
• Reversible strain inversion was observed during the α-to-β phase transition.
• A detailed model of the phase transition was proposed, involving subsurface hydrogen saturation and spherical-cap propagation.

Conclusions:

• The study provides a detailed understanding of the palladium-hydrogen phase transition at the nanoscale.
• The proposed model offers new insights into hydrogen diffusion and phase dynamics in palladium.
• This research has implications for optimizing palladium-based technologies for hydrogen applications.