Microenvironmental Feeding and Stabilization of C₂H₄ Intermediates by Iodide-Doped Copper Nanowire Arrays to Boost C₂H₆ Formation

Abstract

The electroreduction of CO2 provides an attractive routine to produce hydrocarbons as an alternative of traditional petroleum chemical methods, as well as cobenefits the approach of CO2 emission control. Among various C2 hydrocarbons, C2H6 has the highest energy density but poor selectivity in CO2 electroreduction. Thus, the development of highly active catalysts and formation mechanism is desired. Herein, a facile method to synthesize iodide-doped Cu nanoarray (ID-Cu NA) catalysts and a strategy to boost C2H6 electrosynthesis was developed. ID-Cu NAs have dispersive iodide dopants on nanowires, which create a microenvironment to feed, stabilize, and hydrogenate C2H4. This catalyst displays a remarkable selectivity for C2H6 production. Impressively, ID-Cu NAs show a Faradaic efficiency of 24% for C2H6, five times higher than the corresponding Cu NAs before iodide doping. However, the Faradaic efficiency of C2H4 on Cu NAs decreases from 28 to 5% after iodide doping. The results of C2H4 electrodesorption and electrohydrogenation tests indicated that the iodide dopant contributed a more stable C2H4 adsorption and higher hydrogenation ability. Density functional theory calculations demonstrated that the doping of iodide helps to strengthen the adsorption of C2H4 on the Cu surface and lowers the energy barrier of the hydrogenation to C2H6, which simultaneously encourages C2H6 formation in CO2 electroreduction. This work also cleared up the origin of C2H6 formation in CO2 reduction reaction (CO2RR) in which a tandem pathway from CO2 → C2H4 to C2H4 → C2H6 is involved.

Electrode Engineering for Electrochemical CO2 Reduction

“…Excessive CO 2 emissions have led to global warming, a significant problem that all nations need to face and solve immediately. , As a strategic decision for most countries in the world, carbon neutrality is the trend of the times. For example, China plans to reach the peak of carbon dioxide emissions by 2030 and then achieve carbon neutrality by 2060 .…”

Electrochemical CO2 Reduction Catalyzed by Copper Molecular Complexes: The Influence of Ligand Structure

“…The electrochemical CO 2 reduction performances of Cu catalysts prepared by various chemical and electrochemical routes are subject of many excellent publications − ,− and are not discussed here in detail. Before we discuss the catalytic performance of Cu complexes in homogeneous and heterogeneous systems, we nevertheless highlight some specific examples of the CO 2 reduction performance of Cu complex-derived catalysts, specifically deposited using Cu complexes.…”

Electrochemical control of the morphology and functional properties of hierarchically structured, dendritic Cu surfaces

“…Low faradaic efficiencies toward CO and no detectable amount of methane produced by either Cu foam electrocatalyst suggest the structure is capable of suppressing C1 product mechanisms, as has been reported previously. [49][50][51][52] One possible explanation is that CO can be reabsorbed to the electrode surface and undergo further reduction reaction, which becomes more likely in a tortuous structure where the possibility of multiple interactions with the electrocatalyst surface is high. Methane production requires an adsorbed *CO species to go through four hydrogenation reactions without creating C-C dimerization.…”

“…14,54 Methane formation is also a pHdependent process and is less likely within the internal structure of foam electrocatalysts. 3,52 Studies have shown that the pH at the working electrode, the local pH can increase nearly three pH units from the bulk pH of 6.8 due to local hydroxide ion formation during HER and CO2RR. 12,14,[55][56][57] Equation (6) shows the stoichiometrically balanced reaction of CO2 to C2H6…”