Lattice‐Strained <scp> Cu ₂ O </scp> ‐Ni/ <scp>NiO</scp> Heterostructure Enables Selective Electrocatalytic C–C Coupling of Alcohols to Cinnamaldehyde in Aqueous Medium

Electrocatalytic oxidative coupling provides a sustainable route for C–C bond formation between alcohol molecules by precisely regulating the electronic structure of the catalyst and the reaction microenvironment. In this work, we report an electrosynthetic strategy for the directed synthesis of cinnamaldehyde (CAL) through the anodic co‐oxidative coupling of benzyl alcohol (PhCH 2 OH) and ethanol (EtOH) using a Cu 2 O‐Ni/NiO heterogeneous catalyst. The designed heterostructure catalyst possesses dual‐metal synergistic sites to accelerate coupling kinetics and suppress overoxidation of intermediates. Moreover, a salting‐out strategy is introduced to modulate the reaction environment, balancing the rates of selective oxidation and condensation by regulating the hydration behavior and local concentration of reactive aldehyde intermediates. At a current density of 80 mA/cm 2 , this electrosynthetic system achieved an 86% conversion rate for PhCH 2 OH and a selectivity of 67% toward CAL. This work provides new understandings of the interfacial design of non‐noble metal catalysts and electrolyte engineering for selective electrocatalytic coupling reactions, which could be implemented in a wide range of biomass‐derived alcohols upgrading.