Electroreduction of CO2 to value-added chemicals using renewable electricity provides a sustainable route for carbon recycling and fuel production. Accordingly, substantial efforts have been devoted to developing efficient catalysts for electrochemical reduction. However, the activity of electrocatalysts was typically evaluated in conventional H-type cell, in which the slow diffusion of CO2 in liquid electrolyte leads to a mass transport limitation. Accordingly, flow cells with gas-diffusion electrodes (GDEs) are employed to overcome the mass transport limitation, and the local reaction environment in the GDEs can be further tuned to improve the electrocatalysis. Here we report that a hydrophobic microenvironment can significantly enhance the CO2 electroreduction catalysis and improve the activity, Faradaic efficiency, and C2+ product selectivity. To demonstrate such an effect, we use commercial Cu nanoparticles as model catalyst and disperse polytetrafluoroethylene (PTFE) nanoparticles in the catalyst layer, where the hydrophobic PTFE can repel liquid electrolyte and maintain gaseous CO2. Consequently, the PTFE-dispersed electrode achieves a greatly improved activity and Faradaic efficiency for CO2 reduction, with a partial current density &gt;250 mA cm-2 and a single-pass conversion of 14% at moderate potentials, which are almost twice that of a comparative electrode without PTFE addition. As another pivotal role beyond the catalyst materials, the hydrophobic microenvironment builds a delicate balance of gas/liquid in the catalyst layer. At the root of the improved performance metrics are the decreased diffusion layer thickness, accelerated CO2 transport, and increased CO2 local concentration for the catalytic active sites.

Improving CO2 electroreduction catalysis via tuning the hydrophobicity of microenvironment

ACS Fall 2021

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