Evidence for Ambient-Temperature Reversible Catalytic Hydrogenation in Pt-doped Carbons

Abstract

In situ high-pressure Raman spectroscopy, with corroborating density functional calculations, is used to probe C-H chemical bonds formed when dissociated hydrogen diffuses from a platinum nanocatalyst to three distinct graphenic surfaces. At ambient temperature, hydrogenation and dehydrogenation are reversible in the combined presence of an active catalyst and oxygen heteroatoms. Hydrogenation apparently occurs through surface diffusion in a chemisorbed state, while dehydrogenation requires diffusion of the chemisorbed species back to an active catalyst.

Interfacial charge distributions in carbon-supported palladium catalysts

“…Spillover was observed for the Pd/SCCNT samples only above a threshold pressure of 7 bar, similar to previous investigations performed on Pd/C (Supplementary Fig. 14 ) 47 , 50 , 51 .…”

“…The higher reversibility for supports with higher surface oxygen concentration has been documented and it was assigned to ligand-like electron donating/withdrawing effect of the support’s oxygen-containing functional groups 47 , 48 . While this effect was only discussed for small (~ 2 nm) nanoparticles, our results demonstrate that similar trends hold for larger nanoparticles (~ 5 nm) that would otherwise be expected to demonstrate bulk-like properties 47 , 49 . Our combined observations from hydrogen isotherms and XPS provide experimental evidence that supports electron transfer from the metal to the carbon surface.…”

“…Hydrogen spillover was further investigated using high-pressure infrared spectroscopy (HP-FTIR) 47 , 50 , 51 . All samples, both with and without Pd, showed signals characteristic of CH 2 symmetric and asymmetric stretching modes when measured in vacuum (Supplementary Fig.…”

Tracking the Hydrogen Motion in Defective Graphene

“…While scanning tunneling microscopy (STM) investigations of atomic deuterium attached on clean HOPG (0001) surface via plasma treatment indicates the absence of diffusion at room temperature, 19,20 recent Raman and IR studies of different Pt-doped carbon systems report evidence of the H spillover on graphenic surfaces. 21 Also, first-principle molecular dynamics (MD) simulations suggest that chemisorbed hydrogen diffusion onto the graphene plane is feasible and may even compete with desorption. 22 Owing to the large C−H binding energy (≳1 eV), it appears unlikely at first sight that the H atoms jump from one C atom to its neighbor.…”

Revisiting hydrogen spillover in Pt/LTA: Effects of physical diluents having different acid site distributions

“…It is also possible that a series of Lewis acid sites with electron accepting ability may also enable the H migration to occur as a form of H + / e À pair as in the cases of reducible metal oxides [2], which can provide more efficient H migration pathways. Understanding the catalytic functions of H spillover on these non-reducible materials would provide a new insight into the field of heterogeneous catalysis and hydrogen storage [31][32][33].…”