Hydride formation and dynamic phase changes during template-assisted Pd electrodeposition

We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and two-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-phase Pd hydride to alpha-phase Pd. 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.

Automated summary

We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ using various techniques. Our study demonstrated the formation of beta-phase Pd hydride during the bottom-up growth of the nanowires and its phase transition to alpha-phase Pd after electrodeposition was suspended. We also found that grain coalescence hindered the incorporation of hydrogen in the Pd unit cell.