SO₂-Induced Selectivity Change in CO₂ Electroreduction

Abstract

Electrochemical conversion of carbon dioxide (CO2) to value-added chemicals has attracted much attention in recent years as a potential alternative to fossil resources. Although significant works have studied the influence of impurities in the electrolyte (e.g., metal ions), few studies have been performed to understand the influence of gaseous impurities in CO2 electroreduction. Herein, we study the effects of sulfur dioxide (SO2) on Ag-, Sn-, and Cu-catalyzed CO2 electrolysis in a flow-cell electrolyzer in near-neutral electrolyte, representing a broad range of CO2 reduction catalysts. We show that the presence of SO2 impurity reduces the efficiency of converting CO2 due to the preferential reduction of SO2. In the cases of Ag and Sn, the effect of SO2 impurity was reversible and the catalytic activities of both catalysts were recovered. On the contrary, a shift in selectivity toward formate accompanied by a suppression of multicarbon (C2+) products was observed on Cu catalyst, demonstrating that Cu is highly sensitive to SO2 impurity. Our results suggest that CO2 obtained from direct air capture technologies or biorefineries could be more suitable for Cu-catalyzed CO2 electrolysis as these CO2 sources would be relatively cleaner (SO2-free) than fossil-derived sources such as power plants and can be directly coupled with distributed renewable energy sources such as wind and solar.

Insights into the carbon balance for CO2 electroreduction on Cu using gas diffusion electrode reactor designs

“…Thus, the measurement of outlet gas flow in high-rate CO2 reduction plays an important role in calculation of Faradaic efficiency (FE) of gas products. However, currently the majority of work in high-rate CO2 electroreduction [21][22][23]28,[31][32][33][34][35][36] have not explicitly stated that their Faradaic efficiency calculations were based on the outlet gas flow from their reactor (exception for few research on CO2 reduction to CO 37,38 ). Therefore, to ensure results are not errantly reported in GDEs-type electrolyzers, it is critical to fundamentally understand the carbon balance and benchmark the evaluation of the catalytic selectivity (or FE) at high current densities.…”

Single‐Atom Electrocatalysts from Multivariate Metal–Organic Frameworks for Highly Selective Reduction of CO2 at Low Pressures

“…In addition to the active site identification, another critical issue in CO 2 RR is the energy‐consuming capture and purification process of CO 2 . Specifically speaking, to achieve high selectivity, the currently reported CO 2 RR are generally performed in pure CO 2 [30–42] . However, the actual concentration of CO 2 feedstock available from industrial processes such as coal power plant (5–15 % CO 2 ) and steel/petrochemical industry (14–33 % CO 2 ) is relatively low [43–45] .…”

The impact of nitrogen oxides on electrochemical carbon dioxide reduction

“…1a). To date, there are only a few studies focusing on understanding how the presence of contaminants influences the behavior of electrocatalysts under CO 2 RR conditions [15][16][17][18][19][20][21] . For example, NO x is one of the major contaminants present in industrial CO 2 point sources with a typical concentration of 1000 ppm [12][13][14] .…”