10.1021/acsami.7b07611.s001
Mohammed A. Amin
Mohammed A.
Amin
Sahar A. Fadlallah
Sahar A.
Fadlallah
Ghaida S. Alosaimi
Ghaida S.
Alosaimi
Emad M. Ahmed
Emad M.
Ahmed
Nasser Y. Mostafa
Nasser Y.
Mostafa
Pascal Roussel
Pascal
Roussel
Sabine Szunerits
Sabine
Szunerits
Rabah Boukherroub
Rabah
Boukherroub
Room-Temperature
Wet Chemical Synthesis of Au NPs/TiH<sub>2</sub>/Nanocarved Ti Self-Supported
Electrocatalysts for Highly
Efficient H<sub>2</sub> Generation
American Chemical Society
2017
titanium hydride phase
XPS
Tafel slope
TiH 2 phase
RHE
nanocarved Ti substrate self-supported
2 Ti phase
hydrogen evolution reaction
mV
energy conversion devices
0.1 M NH 4 F
Efficient H 2 Generation Self-supported electrocatalysts
NP
SEM
HER
chemical composition TiH 2
GIXRD
as-polished Ti substrates
incidence X-ray diffraction
etching process
TiH 2
nanocarved Ti substrates
X-ray photoelectron spectroscopy
0.1 M KOH solution
room temperature
2017-08-03 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Room-Temperature_Wet_Chemical_Synthesis_of_Au_NPs_TiH_sub_2_sub_Nanocarved_Ti_Self-Supported_Electrocatalysts_for_Highly_Efficient_H_sub_2_sub_Generation/5331541
Self-supported
electrocatalysts are a new class of materials exhibiting
high catalytic performance for various electrochemical processes and
can be directly equipped in energy conversion devices. We present
here, for the first time, sparse Au NPs self-supported on etched Ti
(nanocarved Ti substrate self-supported with TiH<sub>2</sub>) as promising
catalysts for the electrochemical generation of hydrogen (H<sub>2</sub>) in KOH solutions. Cleaned, as-polished Ti substrates were etched
in highly concentrated sulfuric acid solutions without and with 0.1
M NH<sub>4</sub>F at room temperature for 15 min. These two etching
processes yielded a thin layer of TiH<sub>2</sub> (the corrosion product
of the etching process) self-supported on nanocarved Ti substrates
with different morphologies. While F<sup>–</sup>-free etching
process led to formation of parallel channels (average width: 200
nm), where each channel consists of an array of rounded cavities (average
width: 150 nm), etching in the presence of F<sup>–</sup> yielded
Ti surface carved with nanogrooves (average width: 100 nm) in parallel
orientation. Au NPs were then grown <i>in situ</i> (self-supported)
on such etched surfaces via immersion in a standard gold solution
at room temperature without using stabilizers or reducing agents,
producing Au NPs/TiH<sub>2</sub>/nanostructured Ti catalysts. These
materials were characterized by scanning electron microscopy/energy-dispersive
spectroscopy (SEM/EDS), grazing incidence X-ray diffraction (GIXRD),
and X-ray photoelectron spectroscopy (XPS). GIXRD confirmed the formation
of Au<sub>2</sub>Ti phase, thus referring to strong chemical interaction
between the supported Au NPs and the substrate surface (also evidenced
from XPS) as well as a titanium hydride phase of chemical composition
TiH<sub>2</sub>. Electrochemical measurements in 0.1 M KOH solution
revealed outstanding hydrogen evolution reaction (HER) electrocatalytic
activity for our synthesized catalysts, with Au NPs/TiH<sub>2</sub>/nanogrooved Ti catalyst being the best one among them. It exhibited
fast kinetics for the HER with onset potentials as low as −22
mV vs. RHE, high exchange current density of 0.7 mA cm<sup>–2</sup>, and a Tafel slope of 113 mV dec<sup>–1</sup>. These HER
electrochemical kinetic parameters are very close to those measured
here for a commercial Pt/C catalyst (onset potential: −20 mV,
Tafel slope: 110 mV dec<sup>–1</sup>, and exchange current
density: 0.75 mA cm<sup>–2</sup>). The high catalytic activity
of these materials was attributed to the catalytic impacts of both
TiH<sub>2</sub> phase and self-supported Au NPs (active sites for
the catalytic reduction of water to H<sub>2</sub>), in addition to
their nanostructured features which provide a large-surface area for
the HER.