Tuning Cu Overvoltage for a Copper-Telluride System in Electrocatalytic Water Reduction and Feasible Feedstock...

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 Cu_2-Te/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 (R_ct) of 24.4 Ω and, as expected, Cu_2-Te/hyd exhibited a lower Tafel slope value of 188 mV/dec in comparison to Cu_2-Te/wet (280 mV/dec). A chronoamperometry study reveals the long-term stability of both catalysts even up to 12 h. The Faradaic efficiency of Cu_2-Te/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.