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

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-theart 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 & mu;m, 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.