Electrochemical Reduction of Carbon Dioxide to Ethane Using Nanostructured Cu₂O-Derived Copper Catalyst and Palladium(II) Chloride

A method to facilitate the electrochemical reduction of carbon dioxide (CO 2 ) to ethane (C 2 H 6 ) was developed. The electrolyte used was aqueous 0.1 M KHCO 3 . Chronoamperometry, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, online gas chromatography, and nuclear magnetic resonance spectroscopy were used to characterize the electrochemical system and products formed. Carbon dioxide reduction using a Cu 2 O-derived copper working electrode gave ethylene (C 2 H 4 ) and ethanol as main C 2 products, with optimized faradic efficiencies (FE) of 32.1 and 16.4% at −1.0 V vs RHE. The active catalysts were ∼500 nm-sized crystalline Cu 0 particles, which were formed via the reduction of the Cu 2 O precursor during the initial phase of the CO 2 reduction reaction. When palladium(II) chloride was added to the electrolyte, C 2 H 6 formation could be achieved with a significant FE of 30.1% at the said potential. The production of C 2 H 4 was, on the other hand, suppressed to a FE of 3.4%. The alternate use of Pd 0, PdO, or Pd–Al 2 O 3 dopants did not afford the same conversion efficiency. Extensive mechanistic studies demonstrate that C 2 H 4 was first produced from CO 2 reduction at the Cu 0 sites, followed by hydrogenation to C 2 H 6 with the assistance of adsorbed PdCl x . Interestingly, we discover that both Cu and PdCl x sites are necessary for the efficient reduction of C 2 H 4 to C 2 H 6 . The PdCl 2 was “consumed” during the reaction, and a hypothesis for how it contributes to the reduction of CO 2 to ethane is proposed.