Tuning electrochemical environment enables unexpected C=O selectivity for cinnamaldehyde hydrogenation over self-standing palladium cathode.

• Electrochemical-induced switch toward C=O bond in Pd-catalyzed CAL hydrogenation. • The COL selectivity is up to 90% in neutral pH with considerable faraday efficiency. • The self-standing Pd cathode outperforms other catalysts for CAL hydrogenation. • Large π-conjugated system is decisive to C=O selectivity. • Organic solvent retards total hydrogenation of semi-hydrogenated products. It is particularly challengeable to achieve C=O selectivity for Pd catalysts in thermal catalytic hydrogenation of cinnamaldehyde (CAL). This work offers a new electrochemical strategy that enables an unexpected switch toward C=O bond for CAL hydrogenation, based on the specific interaction between CAL and electrolyte-modulated Pd surface. Under galvanostatic electrolysis, guanosine 5′-monophosphate-modulated Pd electrode affords a record cinnamyl alcohol (COL) selectivity of 90.3% in neutral catholyte with no sacrifice of CAL conversion, showing the faradaic efficiency of 68.2%. It is of great interest to find that the aromatic moiety of CAL determines the preferential activation toward C=O bond over Pd surface under electric field. It is reported for the first time that selective hydrogenation of α, β-unsaturated aldehydes can be altered by electrochemical environment located between Pd electrode and surrounding electrolyte involving alkali cation along with organic solvent. [Display omitted] [ABSTRACT FROM AUTHOR]