Facile spray-printing of hydrophobic and porous gas diffusion electrodes enabling prolonged electrochemical CO2 reduction to ethylene

Abstract

The twelve-electron carbon dioxide reduction reaction (12e– CO2RR) constitutes a sustainable alternative to steam cracking for the production of ethylene (C2H4), the world's most coveted organic compound. State-of-the-art gas diffusion electrodes (GDEs), while exhibiting promising faradaic efficiencies for C2H4 electrosynthesis, suffer from poor long-term stability, particularly at elevated applied currents, due to catalyst delamination and flooding of the diffusion layer. Herein, through the development and optimisation of a novel, facile and flexible spray-printing method, hydrophobic porous carbon and copper electrodes with different architectures are obtained readily by using suspensions consisting of two fugitive solvents, which provide larger surface areas for the three-phase boundary and improve the hydrophobicity/flooding tolerance of the electrodes, due to their increased surface roughness and binder (PVDF) content. These structures, with pore sizes as low as 60 μm, transform the surfaces from incomplete wetting to highly hydrophobic, and can be employed as gas-diffusion, microporous or supportive layers, in addition to acting as a supporting substrate for the copper-based catalyst. These layers are spray-printed in a stacked assembly upon polymer film and carbon paper substrates, and ultimately result in an extended duration of enhanced C2H4 production at applied currents of up to 200 mA cm−2 via multiple configurations. Through layer-by-layer spray-printing with a hydrophobic microporous layer and porous catalyst support, this inventive approach can efficiently control the hydrophobicity of the GDE, and extends the cathode operation time by a factor of 6, with a maximum faradaic efficiency of 52% attained, and an average of >30% maintained over 12 h of continuous electrolysis, demonstrating the versatility of this technique for engineering highly durable GDEs for selective CO2 reduction toward multi-carbon (C2+) commodities, energy storage devices and other electrochemical applications.