Macro- and Nano-Porous Ag Electrodes Enable Selective and Stable Aqueous CO2 Reduction

Macro- and Nano-Porous Ag Electrodes Enable Selective and Stable Aqueous CO₂ Reduction

Abstract: Electrochemical carbon dioxide (CO₂) reduction from aqueous solutions offers a promising strategy to overcome flooding and salt precipitation in gas diffusion electrodes used in gas-phase CO₂ electrolysis. However, liquid-phase CO₂ electrolysis often exhibits low CO₂ reduction rates because of limited CO₂ availability. Here, a macroporous Ag mesh is employed and activated to achieve selective CO₂ conversion to CO with high rates from an aqueous bicarbonate solution. It is found that activation of Ag surface using oxidation/reduction cycles produces nanoporous surfaces that favor CO₂-to-CO conversion. Notably, it is found that a combination of dissolved CO₂ in bicarbonate solution with CO₂ generated in situ from bicarbonate ions enables increased CO₂ availability and a CO₂-to-CO conversion rate over 100 mA cm⁻². By optimizing the oxidation/reduction cycles to fine-tune the structure of Ag surface, CO₂-to-CO conversion is reported from a bicarbonate solution with CO Faradaic efficiency of over 85% at current density of 100 mA cm⁻², high concentration of 24.7% at outlet gas stream and stability of over 100 h with maintaining CO FE over 85% during whole reaction time.

Author(s): Behnam Nourmohammadi Khiarak, Gelson T. S. T. da Silva, Valentine Grange, Guorui Gao, Viktoria Golovanova, F. Pelayo de García de Arquer, Lucia H. Mascaro, Cao-Thang Dinh.

Small

Published: 23 December 2024

DOI: https://doi.org/10.1002/smll.202409669

CDMF

The CDMF, hosted at the Federal University of São Carlos (UFSCar), is one of the Research, Innovation and Dissemination Centers (RIDC) supported by the São Paulo State Research Support Foundation (Fapesp), and also receives investment from the National Council Scientific and Technological Development (CNPq), from the National Institute of Science and Technology of Materials in Nanotechnology (INCTMN).