Confinement of Hydrogen Molecules at Graphene–Metal Interface by Electrochemical Hydrogen Evolution Reaction

Abstract

Confinement of hydrogen molecules at graphene–substrate interface has presented significant importance from the viewpoints of development of fundamental understanding of two-dimensional material interface and energy storage system. In this study, we investigate H2 confinement at a graphene–Au interface by combining selective proton permeability of graphene and the electrochemical hydrogen evolution reaction (electrochemical HER) method. After HER on a graphene/Au electrode in protonic acidic solution, scanning tunneling microscopy finds that H2 nanobubble structures can be produced between graphene and the Au surface. Defect dependence of the bubble formation suggests that intrinsic defects in graphene, which have high hydrogen permeation barrier but are permeable for protons, are involved in the fundamental mechanism of bubble formation. Strain analysis by Raman spectroscopy also shows that atomic size roughness on the graphene/Au surface originating from the HER-induced strain relaxation of graphene plays significant role in formation of the nucleation site and H2 storage capacity. The result presented herein would provide further understanding of molecular confinement at graphene-based interface and development of novel energy material.

Terahertz Raman Spectroscopy of Ligand-Protected Au8 Clusters

“…Conversely, as chemical bond lengths are shortened, relative to their normal lengths, Raman peak positions shifted to higher frequencies. [17][18][19] The Aucenter-Aucenter bond for the C4Ph cluster (2.649 Å) is longer than that for the C2Ph cluster (2.628 Å) (Figure 4b). 13,36 Furthermore, the Au6 core breathing mode mainly involves the Aucenter-Aucenter stretching (Figure 3a).…”

“…[15][16] Raman spectroscopy is a powerful technique to observe phonon modes, which are sensitive to the local strain of nanomaterials such as graphene. [17][18][19] Typical Raman spectra recorded in the range from 200 to 4000 cm -1 provide vibrational information on covalent and coordination bonds but not on the gold core unit of gold clusters. To investigate gold cluster vibrations, Raman spectra in the ultra-low frequency region need to be obtained.…”

“…Ultralow-frequency Raman spectroscopy at <200 cm –1 Raman shift (<ca. 6 terahertz (THz)), called THz Raman spectroscopy, can, in principle, give us the direct experimental information on ligand-protected gold clusters on not only core geometrical changes but also the local strain of the core unit caused by core–ligand interactions. , Raman spectroscopy is a powerful technique to observe phonon modes, which are sensitive to the local strain of nanomaterials such as graphene. − Typical Raman spectra recorded in the range from 200 to 4000 cm –1 provide vibrational information on covalent and coordination bonds but not on the gold core unit of gold clusters. To investigate gold cluster vibrations, Raman spectra in the ultralow frequency region need to be obtained.…”

Nanoscale characterization of the site‐specific degradation of electric double‐layer capacitor using scanning electrochemical cell microscopy

“…Nanoscale cell suppresses the capacitive current, provides high faradaic current density and fast electrochemical measurements, and prevents solution-dependent sample contamination. [7,8] SECCM has been used to study the electrochemical activity of HOPG, [9,10] single-carbon nanotubes, [11] polycrystalline Pt, [12][13][14] catalysts for the hydrogen evolution reaction [15][16][17] and CO 2 reduction, [18,19] and battery materials [20][21][22][23][24] to reveal how their electrochemical activities are tied to their structure.…”

A highly durable graphene monolayer electrode under long-term hydrogen evolution cycling

“…In this scenario, the formation of hydrogen bubbles below the graphene sheet may lead to delamination causing physical changes of the graphene sheet. 4,15 Hence, for graphene to be usable as a good candidate for electrocatalysis, it is important that the electrode is durable under continuous gas evolution. Also with an underlying metal surface, the introduction of structural defects on graphene has been proposed as a way to favor hydrogen evolution.…”