Electroreductive C−C Coupling of Benzaldehyde and Its Derivatives over the Ag-Doped In2S3 Catalyst

Abstract Electroreductive C−C coupling of benzaldehyde and its derivatives offers a promising strategy for upgrading the carbon-oxygenates to more valuable compounds by increasing the molecular weight through C−C bond formation. However, limited by the ability to generate ketyl intermediates, the current researches still encounter challenges of low selectivity and productivity that seriously hinder its practical applications. Here, we present a strategy to promote the generation of ketyl intermediates and inhibit the H2O dissociation by introducing Ag on In2S3. The constructed Ag1.6-In2S3 nanocube catalyst can efficiently promote electroreductive coupling of benzaldehyde to produce hydrobenzoin with a high Faradaic efficiency of 98.6% and a productivity of 340.3 μmol h−1 cm−2 at −0.97 V vs RHE, overwhelming most of the reported electrocatalytic works for this reaction. Experimental and theoretical data reveal that the good performance of Ag1.6-In2S3 is attributed to its strong C═O adsorption of benzaldehyde to promote the formation of Ph-C•-OH intermediates for subsequent C−C coupling and poor H2O dissociation activity to inhibit the competitive hydrogen evolution reaction and the generation of byproduct benzyl alcohol. Moreover, the Ag1.6-In2S3 exhibits a broad scope for the electroreduction of various benzaldehyde derivatives to corresponding coupling products. A coupling system that simultaneously realizes the electroreductive coupling to produce hydrobenzoin (at the cathode) and electrooxidation of benzyl alcohol to produce benzaldehyde (at the anode) has also been successfully constructed, demonstrating an economical manner.