Low coordination number copper catalysts for electrochemical CO2 methanation in a membrane electrode assembly

Yi Xu; Fengwang Li; Aoni Xu; Jonathan P Edwards; Sung-Fu Hung; Christine M Gabardo; Colin P O'Brien; Shijie Liu; Xue Wang; Yuhang Li; Joshua Wicks; Rui Kai Miao; Yuan Liu; Jun Li; Jianan Erick Huang; Jehad Abed; Yuhang Wang; Edward H Sargent; David Sinton

doi:10.1038/s41467-021-23065-4

Low coordination number copper catalysts for electrochemical CO₂ methanation in a membrane electrode assembly

Nat Commun. 2021 May 18;12(1):2932. doi: 10.1038/s41467-021-23065-4.

Authors

Yi Xu^#¹, Fengwang Li^#², Aoni Xu², Jonathan P Edwards¹, Sung-Fu Hung^{2

3}, Christine M Gabardo¹, Colin P O'Brien¹, Shijie Liu¹, Xue Wang², Yuhang Li², Joshua Wicks², Rui Kai Miao¹, Yuan Liu², Jun Li^{1

2}, Jianan Erick Huang², Jehad Abed^{2

4}, Yuhang Wang², Edward H Sargent⁵, David Sinton⁶

Affiliations

¹ Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.
² Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada.
³ Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, Taiwan.
⁴ Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada.
⁵ Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada. ted.sargent@utoronto.ca.
⁶ Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada. sinton@mie.utoronto.ca.

^# Contributed equally.

Abstract

The electrochemical conversion of CO₂ to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products. In computational studies herein, we find that copper in a low coordination number favours methane even under highly alkaline conditions. Experimentally, we develop a carbon nanoparticle moderator strategy that confines a copper-complex catalyst when employed in a membrane electrode assembly. In-situ XAS measurements confirm that increased carbon nanoparticle loadings can reduce the metallic copper coordination number. At a copper coordination number of 4.2 we demonstrate a CO₂-to-methane selectivity of 62%, a methane partial current density of 136 mA cm^-2, and > 110 hours of stable operation.