In situ growth of hydrophobic 3D porous Zn@Ag electrode in achieving excellent performance for eCO₂RR

Hydrophobic microenvironment is favorable to CO₂ electroreduction, which can enhance CO₂ transport by overcoming the low solubility limitation of CO₂ in aqueous electrolytes. Up to now, hydrophobic electrode is normally prepared by coating an external hydrophobic layer or by hydrophobic in situ synthesis. Nevertheless, both methods suffer from the low current density of the reaction. To resolve this problem, a three-dimensional (3D) volumetrically electroplated PTFE (polytetrafluoroethylene) porous electrode was produced via PTFE-assisted hydrogen bubble dynamic template method, which has a heterogeneous structure with a hydrophilic surface and hydrophobic interior. The hydrophobic 3D porous Zn@Ag electrode displayed a high activity up to −45 mA cm⁻² with over 92.1 % FE_CO in a microchannel electrolyzer with KHCO₃ solution, which is 3 times higher than a bare ZnAg foam electrode without PTFE (only −15 mA cm⁻² with over 92.0 % FE_CO). Furthermore, it achieved a FE_CO over 91.0 % at a current density up to −250 mA cm⁻² in a flow cell with 1 M KOH electrolyte. The excellent performance was attributed to the accessibility of the active sites to CO₂ in the interior of the electrode, because the pore blocking problem by liquid electrolyte was solved in the case of the hydrophobic interior.