Toward Complete Exfoliation of the Chemisorbed Two-Dimensional Iron Silicates on Ru(0001) via Hydrogenation

Two-dimensional (2D) transition-metal silicates are interesting
materials because of their potential ferromagnetism together with
their inherent piezoelectric response to their structural symmetry.
Substrate-assisted bottom-up synthesis of these materials offers flexibility
in their chemical composition. However, synthesizing free-standing
layers has been challenging because of strong overlayer–substrate
interactions which hinder exfoliation of the overlayer. Here, using
density functional theory calculations, we systematically investigate
the hydrogenation of such overlayers as a way to decrease the substrate–overlayer
interactions. Using the Fe2Si2O8·O/Ru­(0001)
structure as our starting point, we study hydrogenation levels up
to Fe2Si2O9H4/Ru­(0001).
Structural and thermodynamic properties are studied at different hydrogenation
levels to describe the conditions under which exfoliation of the Fe
silicate is feasible. Simulated binding energies of core electrons
show that Fe is primarily in the 3+ state throughout the hydrogenation
process. Simulated reflection adsorption infrared spectroscopy (RAIRS)
yields distinctive shifts in vibrational peaks with increasing hydrogenation
which can guide future experiments.