Silica-copper catalyst interfaces enable carbon-carbon coupling towards ethylene electrosynthesis

Jun Li,Fengwang Li,Edward H Sargent,Dan Ren,Bin Chen,David Sinton,Yuhang Wang,Yi Xu,Michael Graetzel,Fanglin Che,Reza R Zamani,Xue Wang,Yongfeng Hu,Mingyu Wan,Dae-Hyun Nam,Ziyun Wang,Mingchuan Luo,Joshua Wicks,Adnan Ozden

doi:10.1038/s41467-021-23023-0

Abstract

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO2-to-ethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. To date, excessive CO2 coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. With the aid of density functional theory calculations and spectroscopic analysis, here we report an oxide modulation strategy in which we introduce silica on Cu to create active Cu-SiOx interface sites, decreasing the formation energies of OCOH* and OCCOH*—key intermediates along the pathway to ethylene formation. We then synthesize the Cu-SiOx catalysts using one-pot coprecipitation and integrate the catalyst in a MEA electrolyzer. By tuning the CO2 concentration, the Cu-SiOx catalyst based MEA electrolyzer shows high ethylene Faradaic efficiencies of up to 65% at high ethylene current densities of up to 215 mA cm−2; and features sustained operation over 50 h.

Highlights

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO2-toethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle
Excessive local CO2 at the Cu catalyst layer interferes with the adsorption of CO2 electroreduction (CO2RR) intermediates, diminishing the C–C coupling at the Cu surface with limited active sites for ethylene production[17]
We hypothesized that a Cu surface modified with silica could offer a new approach to CO2RR

Summary

Introduction

Membrane electrode assembly (MEA) electrolyzers offer a means to scale up CO2-toethylene electroconversion using renewable electricity and close the anthropogenic carbon cycle. Excessive CO2 coverage at the catalyst surface with limited active sites in MEA systems interferes with the carbon-carbon coupling reaction, diminishing ethylene production. By tuning the CO2 concentration, the Cu-SiOx catalyst based MEA electrolyzer shows high ethylene Faradaic efficiencies of up to 65% at high ethylene current densities of up to 215 mA cm−2; and features sustained operation over 50 h. Gas diffusion electrodes (GDEs) embedded in alkaline flow cell electrolyzers have enabled selective CO2-to-ethylene conversion at industrial-level production rates[6,7]. The membrane electrode assembly (MEA) electrolyzer, with a direct cathode:membrane:anode contact, offers a platform that is more stable than alkaline flow cell electrolyzers[10,11,12]. A low cell resistance of zero-gap MEA electrolyzers enables the use of bicarbonate or carbonate electrolyte without sacrificing the CO2RR efficiency[13,14].

Methods

Results

Conclusion