High‐Yield Electrochemical Production of Formaldehyde from CO 2 and Seawater

The catalytic, electrocatalytic, or photocatalytic conversion of CO 2 into useful chemicals in high yield for industrial applications has so far proven difficult. Herein, we present our work on the electrochemical reduction of CO 2 in seawater using a boron‐doped diamond (BDD) electrode under ambient conditions to produce formaldehyde. This method overcomes the usual limitation of the low yield of higher‐order products, and also reduces the generation of H 2 . In comparison with other electrode materials, BDD electrodes have a wide potential window and high electrochemical stability, and, moreover, exhibit very high Faradaic efficiency (74 %) for the production of formaldehyde, using either methanol, aqueous NaCl, or seawater as the electrolyte. The high Faradaic efficiency is attributed to the sp 3 ‐bonded carbon of the BDD. Our results have wide ranging implications for the efficient and cost‐effective conversion of CO 2 .