Molten Salt Treated Cu Foam Catalyst for Selective Electrochemical CO₂ Reduction Reaction

Abstract

The electrochemical reduction of CO 2 is a promising route to convert waste products to valuable chemicals. Search for suitable and efficient CO 2 reduction electrocatalysts with high C 2 :C 1 selectivity holds great promise. Herein, for the first time we have developed a molten salt oxidized method to modify the morphology and oxidation state of a Cu-foam catalyst. The catalyst displayed a current density of 30 mA cm À 2 (À 1.4 V versus reversible hydrogen electrode) and an ethylene/ methane ratio of 870. We provide insight into the improved performance of the catalysts by cross section scanning transmission electron microscopy and quasi in situ soft X-ray spectroscope, which show that copper oxides are surprisingly reconstructed with Cu (I) and Cu (0) on the surface during the reaction. First principle calculations also demonstrate that the partly reduced Cu 2 O (111) surface has a high reactivity and selectivity for C 2 + products. Furthermore, the molten salt treated catalysts could be applied to the direct synthesis of multi-carbon fuels, including C 3-C 4 compounds in high CO 2 pressure electrocatalytic reduction. Our results demonstrate that molten salt are both the oxidizing agent and reaction medium, which is a promising approach for synthesis of highly active CO 2 electrocatalysts, which may open a new way for industrial application.

Effect of the oxidation state and morphology of SnOx-based electrocatalysts on the CO2 reduction reaction

“…This peak decrease can be related to the Sn 4+ reduction and/or its leaching into the solution. The SEM images showed that the morphology of microsized SnO 2 did not change during the CO 2 RR; however, it could be verified that the SnO 2 particles became less agglomerated and more uniformly dispersed on the carbon fibers, which could relate to the surface reconstruction during CO 2 RR operation, as observed in other studies [41][42][43]. Therefore, the enhanced CO 2 RR performance after the first cycle could also be related to the better distribution of the SnO 2 particles across the carbon fiber surface.…”

Microenvironment Engineering for the Electrocatalytic CO2 Reduction Reaction

“…The molten salt process, in which a molten nitrate functions both as a high‐temperature oxidizing agent and reaction medium, was developed by Wang's group to modify the morphology and oxidation state of a Cu‐foam catalyst (Figure 6e) [73] . The catalyst's surface was enriched with Cu I and Cu 0 sites as verified by the in situ soft XAS measurements.…”

“…[72], Copyright 2020 American Chemical Society, Ref. [73], Copyright 2020 Wiley‐VCH, and Ref. [74], Copyright 2016 American Chemical Society.…”

Microenvironment Engineering for the Electrocatalytic CO2 Reduction Reaction

“… The surface activation of CO 2 RR electrode achieved by executing different treatments, including a–c) gas plasma treatment, [71a–c] d) mass transport control, [72] e) molten salt process, [73] and f) hydrazine treatment [74] . Adapted, with permission, from: Ref.…”

“…[72], Copyright 2020 American Chemical Society, Ref. [73], Copyright 2020 Wiley‐VCH, and Ref. [74], Copyright 2016 American Chemical Society.…”