Inorganic Chemistry
Article
2
2−28
utilized the 3d transition metals, in particular Fe,
chemical feedstock conversion. In this study, the in situ
generated H O from a three-compartment photoelectrobio-
1
8,29−32
17,20,21,26,33
Co,
and Ni,
for the hydrogen evolution
2
2
chemical reactor has been utilized for stable and selective lignin
valorization. To the best of our knowledge, there has been no
report on feedstock conversion by using in situ generated H2.
We are proposing the idea of utilizing the electrochemically
1
8,20,23,29
38,39
58
materials have been well studied. Even though the efficiency
of this 3d transition-metal series in the HER is satisfactory,
further advances are needed. Therefore, to increase the
electrocatalyst performance for the HER, non-noble-metal
generated H in feedstock conversion. A detailed comparison
2
of our protocol with available literature methods is provided
under the section ‘Catalytic Hydrogenation/Hydrogenolysis of
Feedstock Model Compound’ below.
1
1,30,45,46
chalcogenide materials such as sulfides,
sele-
In this work, for the first time we have successfully
developed copper telluride nanochains and aggregates for
HER under aqueous acidic conditions. Also, the performance
of these Cu2−xTe nanochains and aggregates in the HER was
comparatively investigated by varying the synthetic method-
ology by hydrothermal and wet-chemical methods. These
comparative results strongly imply that the catalyst prepared by
the hydrothermal method (Cu2−xTe/hyd) exhibits activity
superior to that of the wet chemical method (Cu2−xTe/wet)
toward the HER. The HER overpotential of Cu2−xTe/hyd
8
,11,26,32,47,48
17,48
nides,
and tellurides
have been incorporated
with these transition metals and show superior electrochemical
activities in the HER. In recent literature, research has been
focused on selenization and sulfurization with transition metals
11
to improve the HER rate. Alshareef et al. carried out
selenization of phase-, surface-, and morphology-engineered
NiCo nanomaterials which results in tremendous activity in the
32
HER with high stability. The tellurides of transition-metal-
based catalysts showed good HER activities. For an examples,
nickel tellurides prepared by Bhat et al. showed an over-
−
2
nanochains is 347 mV to attain 10 mA cm with a low Tafel
slope value of 188 mV/dec. Cu2−xTe/hyd exhibits low charge
transfer resistance and long-term stability in comparison to
Cu2−xTe/wet. Here for the first time, an earth-abundant and
cost-effective metal catalyst for hydrogen production and the
idea of its utilization in environmentally friendly feedstock
conversion by hydrogenation and/or hydrogenolysis reactions
toward various useful chemicals on a large scale by simply
changing reaction conditions in aqueous medium under
external hydrogen pressure is demonstrated. We have chosen
cinnamaldehyde, 2-hydroxy-1-phenylethanone, 4-(benzyloxy)-
benzaldehyde, and 2-(3-methoxyphenoxy)-1-phenylethanone
49
potential of 679 mV and a Tafel slope of 151 mV/dec. In
another interesting work by Wang et al., CoTe nanostructures
2
on carbon fiber paper were prepared and required a much
−
2
lower overpotential of 230 mV at 100 mA cm . Further, it also
delivered high stability even after 5000 cycles and 20 h of
50
prolonged exposure. In an another work by Lu et al., CoTe2
nanostructures with a diameter range of 20−50 nm were
prepared and showed an overpotential of 246 mV at a current
−2
51
density of 10 mA cm .
In this regard, copper (Cu) is the most abundant and
cheapest element in earth for development of an electro-
2
2−25
(
β-O-4 linkage) as model compounds for the selective and
catalyst.
Even though Cu is more earth abundant, its
large-scale conversion of feedstock components by hydro-
genation and/or hydrogenolysis reactions in water under
external hydrogen pressure.
higher overvoltage makes it an unsuitable element for the HER
process. In the literature, copper has been utilized with
equimolar amounts of other noble metals such as Pt, Ag, and
18,23
Au to enhance the HER activity.
Also, to reduce the HER
overpotential of Cu, selenization, phosphorization, and
sulfurization were carried out by using several protocols;
however, the preparation procedure is difficult and/or
EXPERIMENTAL METHODS
■
Synthesis of Cu2 Te Nanochains and Aggregates. Hydro-
−x
thermal and Wet Chemical Methods of Synthesis. The efficient
synthetic methodology to designing a unique and cost-effective
catalyst for the HER is as follows. In order to synthesize the Cu2−xTe
nanochains and aggregates, hydrothermal and wet chemical method-
ologies were carried out (Scheme S1). Here, in the hydrothermal
18,22,24,29
environmentally unfriendly.
To overcome this issue,
a suitable metal partner with Cu is essential to increase the
HER activity of Cu. Along this line, our group proved that
selenization of Cu foam shows higher HER activity than
method of tellurizing copper, the reaction of NaBH with Te powder
2
4
4
pristine copper foam.
Lu et al. have developed Cu3P
was carried initially. In detail, freshly prepared 0.1 M ice-cold NaBH4
was added along with 0.01 M tellurium powder, and the reaction
mixture was heated at 80 °C with gentle stirring for about 15 min; this
resulted in the nucleation of NaHTe. After the immediate formation
of NaHTe, it was further reacted with 0.02 M copper metal ions from
CuCl ·2H O. The probable mechanism in the Cu2−xTe formation is
nanowires by a simple one-step phosphorization, resulting in
5
2
a huge increase in the HER performance. Therefore,
considering the above discussion, we made an attempt to
tellurize copper using hydrothermal and wet chemical methods
to study the HER activity.
2
2
discussed in detail as
In addition, the dual advantage of the developed catalyst was
planned to utilize for fine chemical synthesis the conversion of
feedstock materials derived from agricultural waste products
using hydrogen produced via water electrolysis. The use of
both hydrogenation and hydrogenolysis reactions of feedstock
conversion using hydrogen gas is tuned by an identical catalyst
2
Te + 2NaBH (aq) + 2H O
4
2
−
→ 2NaHTe(aq) + 2B(OH)4 (aq) + H2(g)
2
+
+
+
2NaHTe(aq) + Cu (s) → Cu Te + 2H (aq) + 2Na (aq)
2
−x
25,53,54
has been limited in reports.
Recent reports highlighted
After that, the whole solution mixture was transferred into a 50 mL
Teflon-lined autoclave vessel and kept in a furnace at 180 °C for a
quick time of 3 h. This treatment resulted in a black precipitate that
was washed thoroughly with water and dried at 80 °C for 5 h. The
obtained black powder shows the successful tellurization of copper to
form Cu2−xTe nanochains and is named Cu2−xTe/hyd. Following the
same procedure, the wet chemical method of synthesizing Cu2−xTe
the utilization of oxygen produced from electrocatalytic water
55
splitting for the oxidation of alcohol. Jiang et al. developed a
CeO /ZnIn S hybrid for the selective oxidation of aromatic
2
2 4
alcohols coupled with hydrogen evolution, which highlighted
the dual approach in the production of fine chemicals and H
2
5
6,57
evolution.
Ko et al. recently reported photoelectrobio-
B
Inorg. Chem. XXXX, XXX, XXX−XXX