Tandem Electrocatalytic–Thermocatalytic Reaction Scheme for CO₂ Conversion to C₃ Oxygenates

A two-step tandem electrochemical–thermochemical reaction scheme is demonstrated to convert CO2 into value-added C3 oxygenate molecules: CO2 was electrochemically reduced to ethylene, CO, and H2, followed by the thermochemical hydroformylation reaction to produce 1-propanol and propanal. The CO2 electrolyzer was evaluated with Cu catalysts containing different oxidation states and with modifications to the gas diffusion layer hydrophobicity, while the hydroformylation reactor was tested over a Rh1Co3/MCM-41 catalyst. In situ X-ray absorption spectroscopy showed minimal changes to the Cu and Rh catalysts in the electrochemical and thermochemical reactions, respectively. The tandem configuration achieved a total C3 oxygenate product selectivity (on a basis of reduced CO2) of ∼18%, representing over a 4-fold improvement compared to direct electrochemical CO2 conversion to 1-propanol in flow cells. Additionally, the CO2 electrolyzer was scaled to a 25 cm2 device to enhance the C3 oxygenate production rate up to 11.8 μmol min–1 and demonstrate potential scalability of the tandem system.