Pincer-Copper Polymer Electro-Catalyzed Selective Upgradation of Ethanol to Sodium Acetate
Abstract
The anodic electro-oxidation of ethanol is central to energy conversion, electro-synthesis, and hydrogen-producing electrolyzers, yet the lack of inexpensive electro-catalysts combining high activity and selectivity toward acetic acid, along with durability, remains a critical challenge. Herein, we report the ambient, one-pot Domino synthesis of two pincer-Cu polymers PCuP-SO4 and PCuP-2Br that have integrated earth-abundant copper into a π-conjugated, redox-active, and thermally robust polymeric backbone capable of stabilizing Cu(I). Among the two pincer-Cu polymers, PCuP-SO4 supported on nickel foam (PCuP-SO4/NF) exhibits better ethanol oxidation performance. In 4 M NaOH with 1 M ethanol, PCuP-SO4/NF delivers current densities exceeding 400 mA cm–2, selectivity leads to acetic acid (as sodium acetate) in 98% yield with a Faradaic efficiency of 87% at 1.78 V and maintains high activity under milder alkaline conditions. The relatively better performance of PCuP-SO4 is in agreement with its lower activation energy, lower Tafel slope, lower charge-transfer resistance, higher electrochemically active surface area, and higher diffusion coefficients relative to bare NF, PP/NF, CuSO4/NF, and PCuP-2Br/NF that provide substantially lower acetate yields. Very good recyclability is demonstrated by PCuP-SO4 over at least 10 cycles (cumulative 156081TONs) with minimal leaching of Cu (ca. 0.7%). The activity of PCuP-SO4 is substrate independent, as inferred from the high activity (ca. 97% sodium acetate yield) observed when coated on carbon cloth (CC) instead of NF. Spectroscopic analyses confirm the involvement of dynamic Cu(I)/Cu(II) redox couples during catalysis. The synergistic integration of redox-active Cu centers, labile sulfate anions, and a conductive pincer-polymer scaffold underpins the high selectivity, efficiency, and durability, establishing PCuP-SO4 as a promising anodic catalyst for practical ethanol electro-conversion.