Electrosynthesis of Six-Carbon Acetal from CO₂ Using a Tandem Electrolysis

The conversion of CO2 into high-value chemicals using renewable electricity offers a promising pathway toward carbon neutrality and sustainable chemical production. However, efficiently transforming CO2 into molecules with more than three carbon atoms remains a major challenge. Herein, we propose, for the first time, a tandem electrocatalytic strategy for converting CO2 into the highly valuable six-carbon compound 1,1-diethoxyethane (DEE, valued at ∼$7,000 per ton). This approach couples CO2 electroreduction to ethanol with the subsequent selective electro-oxidation of ethanol to DEE. Key limitations of the latter step, such as low Faradaic efficiency, poor catalyst durability, and dependence on noble metals, are addressed by employing a large-area (100 cm2) electrochemically functionalized graphite flake electrode. This catalyst achieves high FE (>90% across a wide voltage range) and excellent stability (>140 h). Combined theoretical and experimental studies reveal that the COOH functional groups and carbon defects on the graphite synergistically modulate the adsorption of the key CH3CH2O* intermediate, reducing the energy barrier of the rate-determining step. Techno-economic and carbon footprint analyses further demonstrate the economic viability and carbon reduction potential of this tandem process, with an estimated net removal of ∼370 kg of CO2 per ton of DEE produced.