A Pair-Electrosynthesis for Formate at Ultra-Low Voltage Via Coupling of CO(2) Reduction and Formaldehyde Oxidation

Formate can be synthesized electrochemically by CO(2) reduction reaction (CO(2)RR) or formaldehyde oxidation reaction (FOR). The CO(2)RR approach suffers from kinetic-sluggish oxygen evolution reaction at the anode. To this end, an electrochemical system combining cathodic CO(2)RR with anodic FOR was developed, which enables the formate electrosynthesis at ultra-low voltage. Cathodic CO(2)RR employing the BiOCl electrode in H-cell exhibited formate Faradaic efficiency (FE) higher than 90% within a wide potential range from − 0.48 to − 1.32 V(RHE). In flow cell, the current density of 100 mA cm(−2) was achieved at − 0.67 V(RHE). The anodic FOR using the Cu(2)O electrode displayed a low onset potential of − 0.13 V(RHE) and nearly 100% formate and H(2) selectivity from 0.05 to 0.35 V(RHE). The CO(2)RR and FOR were constructed in a flow cell through membrane electrode assembly for the electrosynthesis of formate, where the CO(2)RR//FOR delivered an enhanced current density of 100 mA cm(−2) at 0.86 V. This work provides a promising pair-electrosynthesis of value-added chemicals with high FE and low energy consumption. [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40820-022-00953-y.