Influence of dilute feed and pH on electrochemical reduction of CO2 to CO on Ag in a continuous flow electrolyzer

Abstract

Electrochemical conversion of CO 2 to useful chemical intermediates may be a promising strategy to help reduce CO 2 emissions, while utilizing otherwise wasted excess renewable energy. Here we explore the effect of diluted CO 2 streams (10 to 100% by volume using N 2 as diluting inert gas) on the product selectivity and on the CO/CO 2 conversion ratio for the electrochemical reduction of CO 2 into CO, specifically using a gas diffusion electrode loaded with Ag catalyst in a continuous flow electrolyzer. When using diluted CO 2 feeds for the electrolyzer, we still observed high Faradaic efficiencies for CO (>80%), high conversion ratios (up to 32% per pass), and partial current densities for CO of 29 mA/cm 2 when operating the cell at 3.0 V. Most notably, we observed that the decrease in partial current density for CO was less than 45% when switching from a 100% CO 2 feed to a 10% CO 2 feed. Also, we studied the effect of pH and the interplay between pH and the diluted CO 2 feed. We observed higher levels of CO formation as well as a higher Faradaic efficiency for CO when using an alkaline electrolyte, compared to when using a neutral or acidic electrolyte. However, the effect of CO 2 concentration in the feed is more significant than the effect of pH on electrochemical reduction of CO 2 to CO.

Electrochemical CO₂ Reduction – A Critical View on Fundamentals, Materials and Applications

“…With regard to the CO 2 RR, high current densities of 0.130 A cm -2 for HCOO -production [28] and 0.06 A cm -2 for CO production have been reported for this cell design. [62] These results also prove the versatility of this cell design. Not only (volatile) gaseous reaction products (e.g.…”

Nanostructured nonprecious metal catalysts for electrochemical reduction of carbon dioxide

“…At −0.35 V vs. RHE, the FE reached 94% for CO production and stayed at this level for 6 h without any noticeable change. Similarly, nanostructured Ag and Pd have also shown excellent activity to selectively convert CO 2 to CO [27][28][29][30][31][32][33][34][35][36][37][38]. Nanoporous Ag exhibited an approximately 92% selectivity for CO at a mediocre potential of −0.6 V vs. RHE [35], while on 2.4-and 3.7-nm Pd, a maximum FE value of 91.2% was reached at −0.89 V vs. RHE [38].…”

Electrochemical Reduction of CO2: Effect of Convective CO2 Supply in Gas Diffusion Electrodes

“…Different membrane types have been reported in literature as suitable membrane for the electrochemical reduction of CO 2 , such as cation exchange membranes (CEM), generally Nafion, , anion exchange membranes, bipolar membranes and diaphragms . Nafion, is a thoroughly studied stable membrane with high ionic conductivity.…”