Electrothermal Tandem Catalysis for Acetaldehyde Synthesis From CO2 and Water.

Acetaldehyde (CH3CHO) is an important intermediate in various market sectors, while its industrial production mainly relies on fossil fuels-derived C2H4 and elevated temperature/pressure, leading to massive CO2 emission. In this study, we proposed a novel electrothermal tandem strategy to efficiently synthesize CH3CHO from CO2 and water under mild conditions, by integrating aqueous CO2 electrolysis and Fe3+-promoted Pd2+-catalyzed Wacker oxidation. Specifically, CO2 is electrochemically reduced to C2H4 over Ga-doped Cu/Cu2O hybrid and water is oxidized to O2 over reconstructed Ni5P4 array simultaneously, with respective Faradaic efficiencies of 63.9% and 100%. Then, the generated C2H4 and O2 react with each other in a separate chemical reactor to produce CH3CHO with high production rate of 253.9 µmol h-1 and superior selectivity of 98.3%. Systematic experiments and operando Raman and infrared spectroscopy characterizations verify that the electron-deficient Ga3+ induces electron transfer to stabilize Cu+ species for promoted adsorption and coupling of key *CO intermediates for C2H4 generation, and the Fe3+ cocatalyst with higher oxidative property relative to traditional Cu2+ more effectively alleviates Pd2+ poison caused by CO impurity. This work exhibits tremendous potential for CH3CHO synthesis from CO2 with both economic and environmental benefits.