Atomic Imaging of Subsurface Interstitial Hydrogen and Insights into Surface Reactivity of Palladium Hydrides

Abstract

Resolving interstitial hydrogen atoms at the surfaces and interfaces is crucial for understanding the mechanical and physicochemical properties of metal hydrides. Although palladium (Pd) hydrides hold important applications in hydrogen storage and electrocatalysis, the atomic position of interstitial hydrogen at Pd hydride near surfaces still remains undetermined. We report the first direct imaging of subsurface hydrogen atoms absorbed in Pd nanoparticles by using differentiated and integrated differential phase contrast within an aberration-corrected scanning transmission electron microscope. In contrast to the well-established octahedral interstitial sites for hydrogen in the bulk, subsurface hydrogen atoms are directly identified to occupy the tetrahedral interstices. DFT calculations show that the amount and the occupation type of subsurface hydrogen atoms play an indispensable role in finetuning the electronic structure and associated chemical reactivity of the Pd surface.

Efficient shape transformation of palladium nanocrystals by biphasic oxidative etching and regrowth

“…Both results agree well with our expectations of hydrogen doping into the Pd lattice. 10,[33][34][35][36] The nanocrystals after 2 h of reaction (with NaNO 2 ) show a (111) peak with a d spacing of 2.295 Å, which is in between the d spacing values of Pd (2.246 Å) and PdH 0.706 (2.320 Å). Therefore, the composition of the nanocrystals can be estimated to be PdH 0.47 , according to Vegard's law.…”

Advances and Applications of Atomic-Resolution Scanning Transmission Electron Microscopy

“…For thin specimens, the integrated DPC (iDPC) method (Lazić et al, 2016) possesses advantages for imaging both light and heavy elements (Yücelen et al, 2018). The iDPC STEM imaging method was used to detect hydrogen atoms at metal–metal hydride interfaces (de Graaf et al, 2020) and subsurface interstitial hydrogen in palladium hydrides (Lin et al, 2020). For thicker specimens, large illumination angles may enable accurate structure reconstructions of electric potentials by incorporating probe spreading via a multiple plane phase-contrast transfer function (Brown et al, 2019).…”

Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst

“…33 Generally, catalysts with high thermal conductivity could efficiently avoid local overheating of the surface, which minimizes sintering in thermal catalysis. 33,34 GaN is a metal nitride that has recently been evaluated as a dehydrogenation catalyst. GaN has multifunctional Lewis acid (Ga centers) and base (N centers) sites, which can selectively activate the paraffinic C-H bonds of alkanes.…”

“…33 Generally, catalysts with high thermal conductivity could efficiently avoid local overheating of the surface, which minimizes sintering in thermal catalysis. 33,34…”