High Aspect Ratio Ag Nanowire Mat Electrodes for Electrochemical CO production from CO2

Published

September 13, 2021

Author(s)

David Raciti, Trevor Braun, Brian M. Tackett, Heng Xu, Mutya Cruz, Benjamin Wiley, Thomas P. Moffat

Abstract

An interconnected network of high-aspect ratio Ag nanowires was pressed against porous gas diffusion layers (both conductive or non-conductive) to use as a gas diffusion electrode (GDE) for the electrochemical reduction of CO2 to CO. Varying the amount of Ag nanowires used in the GDE fabrication process allows for systematic evaluation of catalyst layer thickness on the electrode performance in a microfluidic electrolyzer. Thicker catalyst layers favor CO2 reduction to CO over H2 evolution but are also subject to eventually depletion of reactant CO¬2. The partial current for H2 evolution is further suppressed by using a non-conductive PTFE gas-diffusion layer (GDL) rather than the conventional conductive carbon-based GDL. 1-D numerical simulations approximate the complex electrode morphology and microstructure, quantitatively capturing the spatially dependent chemical profiles within the catalyst microenvironment of the GDE during steady-state CO2 reduction. For the operating conditions of interest, the model indicates that catalyst layer thickness plays a significant role in the electrolyte composition and pH within the catalyst microenvironment. Additionally, the model, as well as additional empirical data, reveals that the proton from the dissociation of bicarbonate contributes to the hydrogen evolution reaction. The combination of a self-conductive nanowire catalytic scaffold with a robust hydrophobic porous support structure provides an avenue for the exploration and optimization of the catalyst microenvironment for enhanced yield and selectivity during electrochemical CO¬2 reduction while also diminishing the risk of electrolyte flooding.

Citation

Energy and Environmental Science

Pub Type

Journals

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DOI Link

Keywords

CO2 Conversion, Electrocatalysis, Nanocatalyst Microenvironment, Finite-Element Simulations

Citation

Raciti, D. , Braun, T. , Tackett, B. , Xu, H. , Cruz, M. , Wiley, B. and Moffat, T. (2021), High Aspect Ratio Ag Nanowire Mat Electrodes for Electrochemical CO production from CO2, Energy and Environmental Science, [online], https://doi.org/10.1021/acscatal.1c02783 (Accessed April 26, 2024)