Enzymatic flow electrolyser for the comproportionation of CO2 and organic waste to formate

Paired electrolysis enables the simultaneous coupling of the CO2 reduction reaction (CO2RR) with anodic waste valorisation to form valuable products, but achieving selective, efficient and stable product formation remains a challenge. In this study, W-containing formate dehydrogenase (FDH) from Nitratidesulfovibrio vulgaris Hildenborough is immobilised onto an electrode made from carbon felt coated with porous TiO2 and paired with commercial Ni foam to demonstrate the first enzymatic flow electrolyser for the simultaneous conversion of CO2 and waste (plastic and biomass) to the single product formate. The enzymatic flow electrolyser achieved a combined faradaic efficiency (FE) towards formate of almost 200% for both electrodes and can operate at an unprecedently low full-cell voltage of −1.5 V for 122 h. The aqueous formate produced in the semiartificial electrolyser was further utilised downstream as a C1 building block in the photocatalytic hydrocarboxylation of alkenes, providing a path for the domino valorisation of CO2 and waste towards bulk and fine chemical synthesis.