Cu2O-loaded gas diffusion electrodes for the continuous electrochemical reduction of CO2 to methanol

- Gas-diffusion electrodes are prepared with Cu2O-ZnO particles for CO2 valorization.
- The electroreduction process gave mainly methanol, and also ethanol and n-propanol.
- The production rate and process efficiency greatly depended on the current applied.
- Cu2O/ZnO surfaces are expected to remain stable for over 20 h.
- The electrolyte and CO2 flows showed an optimal point for mass transfer.

Gas-diffusion electrodes are prepared with commercial Cu2O and Cu2O-ZnO mixtures deposited onto carbon papers and evaluated for the continuous CO2 gas phase electroreduction in a filter-press electrochemical cell. The process mainly produced methanol, as well as small quantities of ethanol and n-propanol. The analysis includes the evaluation of key variables with effect in the electroreduction process: current density (j = 10-40 mA cm−2), electrolyte flow/area ratio (Qe/A = 1-3 ml min−1 cm−2) and CO2 gas flow/area ratio (Qg/A = 10-40 ml min−1 cm−2), using a 0.5 M KHCO3 aqueous solution.The maximum CO2 conversion efficiency to liquid-phase products was 54.8% and 31.4% for Cu2O and Cu2O/ZnO-based electrodes at an applied potential of −1.39 and −1.16 V vs. Ag/AgCl, respectively. Besides, the Cu2O/ZnO electrodes are expected to catalyze the CO2 electroreduction for over 20 h. These results may provide new insights into the application of gas diffusion electrodes to alleviate mass transfer limitations in electrochemical systems for the transformation of CO2 to alcohols.

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