Anodic Oxidation of Methanol to Formaldehyde Synergizing with a Br-/Br2 Redox-Mediated Chemical Route to Produce Methyl Formate.

Methyl formate (MF) is one of the most important chemical commodities, which has a wide range of applications. Due to environmental friendliness, mild reaction conditions, and easy operations, electrosynthesis of MF has garnered increasing attention in recent years. In this work, we reported an electrosynthesis route toward MF in a halide-containing methanol solution. The thorough mechanistic investigations point out that electrosynthesis of MF is accomplished by instant reaction between aldehyde from anodic methanol oxidation, and methoxy bromide (CH3OBr) that is in-situ generated by reaction of Br2 from anodic oxidation of Br- with methoxide (CH3O-) from cathodic reduction of methanol. This method features high atomic economy only producing valuable MF and hydrogen gas, and shows distinct advantages compared to the reported MF electrosynthesis methods. Even at 200 mA/cm2, the faradaic efficiency (FE) of MF remains consistently around 60 % at the anode while a 100 % FE hydrogen gas is produced at the cathode.