Graphical Roughness-dependence of Cu electrodes is for the first time identified in the electro-reductive coupling of nitro and carbonyl compounds. With increased roughness, the selectivity of nitrones decreases, while that of imines increases, thanks to the feasible control over the reduction of nitroarenes to hydroxylamines or amines on Cu I /Cu 0 interfaces. The electro-reductive coupling of nitro and carbonyl compounds enables a facile, environmentally friendly and energy benign transformation toward value-added nitrones or imines, but the selectivity is still challenging. Here, the surface roughness of Cu electrodes is introduced for the first time as the determinant to switch products from nitrones to imines owing to the controllable reduction of nitroarenes to hydroxylamines or amines on tailored Cu I /Cu 0 interfaces. The roughness-dependent selectivity, that is the decrease of nitrones and the increase of imines with enhanced roughness, is visible in the electro-reductive coupling of nitrobenzene and furfural. Thus, the high selectivity of nitrone (98 %) and imine (80 %) can be achieved on a surface smooth Cu foil and the one electrochemically roughened in the presence of I − , respectively. Such roughness-dependence of nitrone/imine selectivity on Cu electrodes is further verified in a wide substrate scope, highlighting the promise of surface/interfacial engineering for electrochemical synthesis.
Rongming Cai,Mingzi Sun,Fei Yang,Min Ju,Yanpeng Chen,M. Danny Gu,Bolong Huang,Shihe Yang
Summary By leveraging a Cu(OH)F precursor, we construct a disk-like Cu(I)/Cu(0) interface model (P-Cu x /Cu 2 OF) composed of F-stabilized Cu(I) shell and Cu(0) core by one-step pulsed potential conversion. The interfacial region is shown to facilitate ethanol formation, guaranteeing a high FE(C 2+ ) of up to 80.2%. Tuning the Cu(I)/Cu(0) ratio enhances the ethanol yield by 18.5-fold over pure P-Cu, with the corresponding partial current density (j ethanol ) reaching up to 128 mA/cm 2 . This is enabled by a 3.6-fold boost in selectivity for the ethanol product (35.4%) and an overall 7.8-fold boost in activity ( j C 2 + up to 288 mA/cm 2 ). The interactions between P-Cu and Cu 2 OF upshift the d-band center of Cu sites on the interface region, which is critical to asymmetrical C-C coupling to form OCCOH∗, concurrent with a lowered energy barrier for ethanol formation. On the other hand, the ethylene-forming symmetrical C-C coupling occurs primarily on P-Cu away from the Cu(I)/Cu(0) interface.
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