Selective CO₂ Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte‐Driven Nanostructuring

Abstract

Production of multicarbon products (C 2+ )from CO 2 electroreduction reaction (CO 2 RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO 2 RR catalysts that are highly selective for C 2+ products via electrolyte-driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO 2 into ethylene and multicarbon alcohols in aqueous 0.1m KHCO 3 solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of 80 %a nd ap artial geometric current density of ca. 31.2 mA cm À2 for C 2+ products at À0.9 V vs.RHE. Operando X-rayabsorption spectroscopyand quasi in situ X-rayp hotoelectron spectroscopym easurements revealed that the high C 2+ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis,p resence of subsurface oxygen and Cu + species,and the adsorbed halides.

Electrochemical CO2 Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes

“…This sudden change in C 2+ selectivity implies a changed reaction mechanism and can be explained by an increase in local pH due to high proton consumption at high current densities together with the phenomenon's described above. [ 65,68,69 ] The composition of the product gas stream is 37.0 vol% H 2 , 10.8 vol% CO, and 6.2 vol% ethylene along with traces of ethane (250 ppm) as well as CO 2 (Table S10, Supporting Information). However, further increasing the current density to 300 and 400 mA cm −2 , the total detected faradaic efficiency decreased significantly to 67% at 400 mA cm −2 .…”

In Situ/Operando Electrocatalyst Characterization by X-ray Absorption Spectroscopy

“…The presence of specific anions can also affect the stability of Cu(I) species and the catalyst performance. In ref ( 423 ), nanostructured Cu catalysts prepared by cycling electropolished Cu foils in the presence of Cl – , Br – , I – , and CO 3 2– anions were investigated. While EXAFS analysis of all samples under CO 2 RR conditions showed a predominantly metallic structure, the HERFD-XANES method, more sensitive to the oxidation state of the catalyst, showed that Cu(I) species are present in some of the halide-modified catalysts.…”

“…A positive correlation between the amount of Cu(I) species detected by HERFD-XANES, and the yield of C 2+ products was observed. 423 In another recent study that focused on the effect of halide ions, Cu 2 O microspheres were electroreduced in the presence of iodine, which resulted in porous Cu structures. When exposed to CO 2 RR conditions, this catalyst yielded a significantly improved selectivity for C 2+ products as compared to pristine metallic Cu.…”

Highly Efficient Electroreduction of CO2 to C2+ Alcohols on Heterogeneous Dual Active Sites

“…[16][17][18][19] However, the most Cu-based catalysts generally favor the production of ethylene during CO 2 RR. [20][21][22][23] To improve the selectivity of C2 + alcohols, different methods have been applied to modify the Cu-based catalysts, including modifying morphology, [24] using two metals, [25] doping with a heteroatom, [26] and modifying with other molecules. [27] These methods mainly increase the production of the key C1 intermediate (CO) by another component to further enhance the production of alcohols, because the selectivity of C2 + products can be tuned by the coverage of CO. [28] Despite these impressive efforts, the Faradaic efficiency (FE) of C2 + alcohols remains below 43 % at commercial current density (!…”