$\textit{In situ}$ hydride breathing during the template-assisted electrodeposition of Pd nanowires

TL;DR

This study uses in situ x-ray scattering and other techniques to analyze how hydrogen interacts with palladium nanowires during electrodeposition, revealing phase transitions and structural evolution influenced by hydrogen incorporation.

Contribution

It provides the first in situ analysis of hydride phase formation and transition during Pd nanowire electrodeposition, highlighting the interplay between growth, hydrogen absorption, and grain coalescence.

Findings

Formation of $eta$-phase Pd hydride during growth

Transition from $eta$- to $ extalpha$-phase Pd hydride upon suspension

Grain coalescence reduces hydrogen incorporation

Abstract

We investigated the structural evolution of electrochemically fabricated Pd nanowires $\textit{in situ}$ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and 2-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that $\beta$-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from $\beta$- to $\alpha$-phase Pd hydride. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.