Electroreductive coupling of benzaldehyde by balancing the formation and dimerization of the ketyl intermediate.

Electroreductive coupling of biomass-derived benzaldehyde offers a sustainable approach to producing value-added hydrobenzoin. The low efficiency of the reaction mainly ascribes to the mismatch of initial formation and subsequent dimerization of ketyl intermediates (Ph-CH = O → Ph-C·-OH → Ph-C(OH)-C(OH)-Ph). This paper describes a strategy to balance the active sites for the generation and dimerization of ketyl intermediates by constructing bimetallic Pd/Cu electrocatalysts with tunable surface coverage of Pd. A Faradaic efficiency of 63.2% and a hydrobenzoin production rate of up to 1.27 mmol mg⁻¹ h⁻¹ (0.43 mmol cm⁻² h⁻¹) are achieved at −0.40 V vs. reversible hydrogen electrode. Experimental results and theoretical calculations reveal that Pd promotes the generation of the ketyl intermediate, and Cu enhances their dimerization. Moreover, the balance between these two sites facilitates the coupling of benzaldehyde towards hydrobenzoin. This work offers a rational strategy to design efficient electrocatalysts for complex reactions through the optimization of specified active sites for different reaction steps.Electroreductive coupling of benzaldehyde is mainly hindered by the mismatch between initial formation and subsequent dimerization of the ketyl intermediates. Here the authors report a strategy to balance the active sites for the generation and dimerization of the ketyl intermediates, leading to promoted production rate of hydrobenzoin. [ABSTRACT FROM AUTHOR]