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
Abstract
Abstract The electrochemical conversion of CO 2 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 CO 2 -to-methane selectivity of 62%, a methane partial current density of 136 mA cm −2 , and > 110 hours of stable operation.