Paired production of formic acid/formate by cathodic reduction of CO2 at Sn and anodic oxidation of methanol at BDD

Abstract

The paired synthesis of formic acid/formate (FA) via CO2 cathodic reduction and methanol anodic oxidation was investigated using a tin cathode and, for the first time, a boron doped diamond (BDD) anode. To select the most suitable operative conditions for the paired process, the influence of several parameters, such as the nature of the supporting electrolyte (SE), the concentration of both SE and CH3OH, and the temperature, was studied in detail for both cathodic and anodic processes. In particular, the effect of SE nature was thoroughly evaluated by testing SEs containing different cations (K+, Na+ and Cs+) and anions (SO42-, OH-, and HCO3-). The results show that the use of a BDD anode and of a tin cathode allows to obtain very high faradic efficiencies for both cathodic and anodic processes under optimized operating conditions, especially when operating with 0.1 M Na2SO4 as SE in the catholyte and 0.5 M NaOH + 0.5 M CH3OH in the anolyte.