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

Abstract

A method to facilitate the electrochemical reduction of carbon dioxide (CO2) to ethane (C2H6) was developed. The electrolyte used was aqueous 0.1 M KHCO3. 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 Cu2O-derived copper working electrode gave ethylene (C2H4) and ethanol as main C2 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 Cu0 particles, which were formed via the reduction of the Cu2O precursor during the initial phase of the CO2 reduction reaction. When palladium­(II) chloride was added to the electrolyte, C2H6 formation could be achieved with a significant FE of 30.1% at the said potential. The production of C2H4 was, on the other hand, suppressed to a FE of 3.4%. The alternate use of Pd0, PdO, or Pd–Al2O3 dopants did not afford the same conversion efficiency. Extensive mechanistic studies demonstrate that C2H4 was first produced from CO2 reduction at the Cu0 sites, followed by hydrogenation to C2H6 with the assistance of adsorbed PdCl x . Interestingly, we discover that both Cu and PdCl x sites are necessary for the efficient reduction of C2H4 to C2H6. The PdCl2 was “consumed” during the reaction, and a hypothesis for how it contributes to the reduction of CO2 to ethane is proposed.

In situ spectroscopic monitoring of CO2 reduction at copper oxide electrode

“…As discussed in the introduction, prevailing opinion is that copper oxide materials must first be reduced to copper to be effective CO2 electrocatalysts [9][10][11][12][16][17][18] . This study does not contradict this, as it likely that the copper produced during reduction is a 30 more active catalyst for CO2 reduction than CuO.…”

“…The use of copper oxide electrodes in this application was first reported in 1991 8 , but 35 the field has undergone a massive resurgence over the past five years [9][10][11][12][13][14][15][16][17][18] . It has been noted by many researchers that copper electrode surface morphology and nanostructure and the presence of surface oxides plays a large rol e in determining product distribution and efficiency [9][10][11][12][13][14][15][16][17][18] .…”

“…It has been noted by many researchers that copper electrode surface morphology and nanostructure and the presence of surface oxides plays a large rol e in determining product distribution and efficiency [9][10][11][12][13][14][15][16][17][18] . For this reason, the role of copper oxides and their reduction products in CO2 reduction has been studied recently using a wide range 40 of techniques, including X-ray diffraction 9-12 , Auger 8,13,14 , X-ray photoelectron spectroscopy (XPS) 10,11,13 , temperature programmed desorption 15,16 , X-ray absorption spectroscopy 14,15,17 . Relatedly, semiconducting copper oxides are also proposed as electrodes are formed through annealing of copper in air to form thick Cu 2O films and are proposed to retain metastable Cu(0) sites at grain boundaries when electrochemically reduced 12 .…”

Electrocatalytic CO2 Reduction to Formate at Low Overpotentials on Electrodeposited Pd Films: Stabilized Performance by Suppression of CO Formation

“…Several electrodes, such as various metallice lectrodes, [2,4,14,15] metal sulfides, [16,17] metal complexes, [6] and others, [18] have been investigated, and the electrode materiala nd structure affect significantly the CO 2 reduction selectivity and stability. [23] Ye and co-workersp repared mesoporousP d-Cu electrocatalysts, and Pd 7 Cu 3 nanoparticles exhibited ah igh FE (80 %a t À0.8 V) for CO. [24] If Pd is combined with Au, which binds only weakly with CO, multi-carbon products can be produced through CO 2 reduction. [22] The FE of CO production is much higher on small Pd nanoparticles (91.2 %f or 3.7 nm) than on those of larger sizes (5.8 %f or 10.3 nm).…”

Synthesis and Characterization of Degradation‐Resistant Cu@CuPd Nanowire Catalysts for the Efficient Production of Formate and CO from CO2

“…According to the literature, a number of CuPd nanoalloys have already been applied in the CO 2 RR . Yin et al studied compositional effcets of CuPd alloy nanoparticles supported on carbon on the catalyst activity.…”