Bioelectrochemical system (BES) was operated using the enzyme formate dehydrogenase as catalyst at cathode in its free form for the reduction of CO2 into formic acid.
Electrosynthesis of formic acid was higher at an operational voltage of −1 V vs. Ag/AgCl (9.37 mg L−1 CO2) compared to operation at −0.8 V (4.73 mg L−1 CO2) which was strongly supported by the reduction catalytic current. Voltammograms also depicted a reversible redox peak throughout operation at −1 V, indicating NAD+ recycling for proton transfer from the source to CO2. Saturation of the product was observed after 45 min of enzyme addition and then reversibility commenced, depicting a lower and stable formic acid concentration throughout the subsequent time of operation.
Stability of the enzyme activity after immobilization on the electrode and product yield will be studied further.