Tuning Cu Overvoltage for a Copper-Telluride System in Electrocatalytic Water Reduction and Feasible Feedstock Conversion: A New Approach.
2020
Highly
efficient and earth-abundant elements capable of water reduction
by electrocatalysis and are attractive for the sustainable generation
of fuels. Among the earth-abundant metals, copper is one of the cheapest
but often the most neglected choice for the hydrogen evolution reaction
(HER) due to its high overvoltage. Herein, for the first time we have
tuned the overpotential of copper by tellurizing it by two different
methodologies, viz. hydrothermal and wet chemical methods, which form
copper telluride nanochains and aggregates. The application of copper
telluride as an electrocatalyst for the HER gave fruitful results
in terms of both activity and stability. The hydrothermally synthesized
catalyst Cu2–xTe/hyd shows a low
overpotential (347 mV) at 10 mA cm–2 toward the
HER. In addition, the catalyst showed a very low charge transfer resistance
(Rct) of 24.4 Ω and, as expected,
Cu2–xTe/hyd exhibited a lower Tafel
slope value of 188 mV/dec in comparison to Cu2–xTe/wet (280 mV/dec). A chronoamperometry study reveals
the long-term stability of both catalysts even up to 12 h. The Faradaic
efficiency of Cu2–xTe/hyd was calculated
and found to be 95.06% by using gas chromatographic (GC) studies.
Moreover, with the idea of utilizing produced hydrogen (H2) from electrocatalysis, for the first time we have carried out feedstock
conversion to platform chemicals in water under eco-friendly green
conditions. We have chosen cinnamaldehyde, 2-hydroxy-1-phenylethanone,
4-(benzyloxy)benzaldehyde, and 2-(3-methoxyphenoxy)-1-phenylethanone
(β-O-4) as model compounds for feedstock conversion by hydrogenation
and/or hydrogenolysis reactions in aqueous medium using external hydrogen
pressure. This protocol could also be scaled up for large-scale conversion
and the catalyst is likely to find industrial application since it
requires an inexpensive catalyst and an easily available, mild reducing
agent. The robustness of the developed catalyst is proven by recyclability
experiments and its possibility of use in real-life applications.
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