Electroreduction of carbon dioxide to formate at high current densities using tin and tin oxide gas diffusion electrodes

Abstract

We investigate tin (Sn) and tin oxide (SnO 2 ) nanoparticle catalysts deposited on gas diffusion layers for the electrochemical reduction of carbon dioxide (CO 2 ) to formate. The performance and durability of these electrodes was evaluated in a gas-fed electrolysis cell with a flowing liquid electrolyte stream and an integrated reference electrode. The SnO 2 electrodes achieved peak current densities of 385 ± 19 mA cm -2 while the Sn electrodes achieved peak current densities of 214 ± 6 mA cm -2 , both at a formate selectivity > 70%. The associated peak formate production rates of 7.4 ± 0.6 mmol m -2 s -1 (Sn) and 14.9 ± 0.8 mmol m -2 s -1 (SnO 2 ) were demonstrated for a 1 h electrolysis and compare favorably to prior literature. Post-test analyses reveal chemical and physical changes to both cathodes during electrolysis including oxide reduction at applied potentials less than -0.6 V vs. RHE, nanoparticle aggregation, and catalyst layer erosion. Understanding and mitigating these decay processes is key to extending electrode lifetime without sacrificing formate generation rates or process efficiency.

Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

“…For all experiments, Ag‐GDE cathodes were loaded into the cell shown in Figure (bottom) along with a metallic Ni anode and a Hg/HgO reference electrode to enable independent measurement of individual electrode polarizations. The cell geometry was originally developed by our group as a small‐scale redox flow battery testing platform and was recently adapted for a catalytic study of tin and tin oxide GDEs for electroreduction of CO 2 to formate in a gas‐fed, flowing alkaline electrolyte configuration . In this study, the cathode side was outfitted with a serpentine flow field machined from polymer‐impregnated graphite and operated in gas‐phase delivery mode.…”

Investigating Electrode Flooding in a Flowing Electrolyte, Gas-Fed Carbon Dioxide Electrolyzer

“…The cell geometry was originally developed by our group as a small-scale redox flow battery testing platform [44] and was recently adapted for a catalytic study of tin and tin oxide GDEs for electroreduction of CO2 to formate in a gas-fed, flowing alkaline electrolyte configuration. [45] In this study, the cathode side was outfitted with a serpentine flow field machined from polymer-impregnated graphite and operated in gas-phase delivery mode. The serpentine flow field both provides electrical contact to the GDE and facilitates liquid removal by flowing gas, which allows experiments to continue until the advanced stages of electrode flooding.…”

From CO2 to Bioplastic – Coupling the Electrochemical CO2 Reduction with a Microbial Product Generation by Drop‐in Electrolysis

“…Hydrogen evolution was observed during all electrolyses and is assumed to be the main unfavourable side reaction limiting the current efficiency. [13,15,16,27] However, formation of CO as it has been reported as alternative side reaction besides hydrogen evolution [13] cannot be excluded, but has not been examined.…”

“…Thereby, Sn was applied as main electro-catalyst in the GDE. [13][14][15][16][17][18] In batch processes, FE up to 90 % have been reported at current densities in range of À 50 to À 200 mA cm À 2 . [13] In continuous processes, several studies demonstrated FE between 70 und 75 % at current densities as high as À 100 to À 400 mA cm À 2 .…”

“…[13] In continuous processes, several studies demonstrated FE between 70 und 75 % at current densities as high as À 100 to À 400 mA cm À 2 . [15][16][17] On the one hand side, electrochemical formate synthesis is a rather far developed technology for the storage of energy and CO 2 binding compared to alternative electrochemical CO 2 reduction routes besides syngas. On the other hand side, formate also offers great advantages as sustainable microbial feedstock for biotechnological transformation processes and the generation of higher value products, since it can be used as sole carbon source and serve as electron carrier in microbial electrosynthesis processes.…”