Collision-Induced Desorption and Reaction on Hydrogen-Covered Al(111) Single Crystals:  Hydrogen in Aluminum?

Abstract

We examine the recombination and desorption of hydrogen from an aluminum(111) surface focusing on desorption processes that lead to the formation of dihydrogen and aluminum hydride (presumably alane). In addition to simple temperature-programmed reaction spectroscopy (TPRS), we examine the perturbations which occur to the desorption kinetics of these species as a result of the energy transfer due to collisions of a xenon beam at 1.6, 2.8, and 3.6 eV with a hydrogen covered surface. Whereas the recombinative desorption of dihydrogen from an Al(111) surface nominally follows an unusual zero-order rate law, bombardment of a hydrogen-covered surface with an energetic xenon atom leads to a kinetic profile more closely modeled by a higher reaction order. It also was found that upon exposure to the beam, the peak area (and thus the desorption yield) for the H2 desorption was reduced 5−25% depending on the length of exposure whereas for the aluminum hydride the percent reduction ranged from 10−80%. This suggests that both a stimulated etching and a change in state result from the beam exposure. We present evidence that suggests that the initial state of the bound hydrogen may involve at least in part a subsurface occupation.

Formation of Aluminum Hydride during Alkaline Dissolution of Aluminum

“…and the H-induced etching of aluminum to form hydride, as has been extensively observed in vacuum experiments [25][26][27][28][29][30] Al + 3H → AlH 3 ͓3͔…”

Participation of Aluminum Hydride in the Anodic Dissolution of Aluminum in Alkaline Solutions

“…[13][14][15][16][17][18] The hydride then oxidized according to the reaction identified by Perrault The present paper examines whether the electrochemical behavior of anodic Al dissolution in alkaline solutions supports the participation of AlH 3 as a reaction intermediate. Results of cyclic voltammetry ͑CV͒ and potential step experiments are interpreted using models for the Al electrode based on the proposed mechanism.…”

Hydrogen atom adsorption on aluminum icosahedral clusters: A DFT study

“…These findings are important because light metals such as aluminum are inexpensive and can store large amounts of hydrogen, which is crucial for fuel cell design [4]. Crane and Nuzzo [5] obtained evidence related to H adsorption on Al(1 1 1). Through careful examination of temperature-programmed desorption data, they suggested that chemisorbed H on Al(1 1 1) occupies both surface and subsurface sites.…”