April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)
Symposium Supporters
2024 MRS Spring Meeting
EN09.05.05

Cation Exchange Ionomer-Based Microenvironment Control of Gas Diffusion Electrode for Efficient CO2 Electroreduction

When and Where

Apr 24, 2024
9:30am - 9:45am
Room 337, Level 3, Summit

Presenter(s)

Co-Author(s)

Yujin Lee1,Daewon Bae1,Woosuck Kwon1,Hansol Choi2,Hyungju Ahn3,Chang Hyuck Choi2,Chanyeon Kim1,Dae-Hyun Nam1

Daegu Gyeongbuk Institute of Science & Technology (DGIST)1,Pohang University of Science and Technology (POSTECH)2,Pohang Accelerator Laboratory (PAL)3

Abstract

Yujin Lee1,Daewon Bae1,Woosuck Kwon1,Hansol Choi2,Hyungju Ahn3,Chang Hyuck Choi2,Chanyeon Kim1,Dae-Hyun Nam1

Daegu Gyeongbuk Institute of Science & Technology (DGIST)1,Pohang University of Science and Technology (POSTECH)2,Pohang Accelerator Laboratory (PAL)3
Electrochemical CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) where CO<sub>2</sub> is converted into a high-value-added compound can be a great strategy for carbon neutrality. Gas diffusion electrode (GDE) which allows the formation of triple phase boundary (TPB) of catalyst, electrolyte, and CO<sub>2</sub> gas has been widely applied for CO<sub>2</sub>RR. It results in overcoming the CO<sub>2</sub> solubility limitation in double phase boundary (DPB) of electrolyte and catalyst, and thus increases the CO<sub>2</sub> availability. However, the volume of TPB where the reaction occurs is much smaller than the volume of DPB. Therefore, it is important to increase the volume of TPB for CO<sub>2</sub>RR activity. Cation exchange ionomer enables us to control the volume of TPB. The hydrophobic chains of ionomer that play a role as gas channel and hydrophilic ionic groups that form a water matrix increase the volume of TPB in GDE-based systems.<br/>Here, we verify the effect of ionomer on CO<sub>2</sub>RR performance in 1 M KOH electrolyte by controlling CO<sub>2</sub>/H<sub>2</sub>O ratio and CO<sub>2</sub> availability near GDE-based Cu catalyst surface. To distinguish the effect of each part of ionomer, we control the variables of ionomer; (1) Controlling the length of side chain with the application of Nafion as long side chain (LSC) ionomer and Aquivion as short side chain (SSC) ionomer, (2) Fixation of equivalent weight (EW). Compared to the maximum H<sub>2</sub> partial current density (J<sub>H2</sub>) of 71.3 mA/cm<sup>2 </sup>at bare Cu, Nafion decreases the maximum J<sub>H2</sub> to 11.5 mA/cm<sup>2</sup> while Aquivion decreases it to 26.4 mA/cm<sup>2</sup>. On the other hand, the maximum CO partial current density (J<sub>CO</sub>) is 75.1 mA/cm<sup>2</sup> at Nafion whereas it is 24.1 mA/cm<sup>2 </sup>at Aquivion. Nafion and Aquivion also improve the maximum C<sub>2</sub>H<sub>4</sub> partial current density (J<sub>C2H4</sub>) to 169.5 and 173.3 mA/cm<sup>2</sup>, respectively. Based on the characterization of ionomers in GDE, we found that LSC ionomer can induce a higher CO<sub>2</sub>/H<sub>2</sub>O ratio than SSC ionomer and increase CO<sub>2</sub> availability near the active site. Also, we assume that it affects the CO<sub>2</sub>RR selectivity by tuning the local OH<sup>-</sup> concentration. Improved OH<sup>-</sup> formation by high current density CO<sub>2</sub>RR at ionomer-augmented catalysts affects the surface charge density that can enhance CO<sub>2</sub>RR selectivity. Therefore, the key factor of ionomer effect on CO<sub>2</sub>RR performance enhancement is regulation of the water concentration near the catalyst surface which impacts the CO<sub>2</sub> availability and ion conductivity through this water matrix. We expect that this work will suggest a more accurate understanding of the mechanism of ionomer effect on CO<sub>2</sub>RR and strategy for optimizing the microenvironment of catalyst for efficient CO<sub>2</sub>RR.

Keywords

Cu

Symposium Organizers

Christopher Barile, University of Nevada, Reno
Nathalie Herlin-Boime, CEA Saclay
Michel Trudeau, Concordia University
Edmund Chun Ming Tse, University Hong Kong

Session Chairs

Michel Trudeau
Edmund Chun Ming Tse

In this Session