Gas diffusion enhanced electrode with ultrathin superhydrophobic macropore structure for acidic CO₂ electroreduction

Carbon dioxide (CO₂) electroreduction reaction (CO₂RR) offers a promising strategy for the conversion of CO₂ into valuable chemicals and fuels. CO₂RR in acidic electrolytes would have various advantages due to the suppression of carbonate formation. However, its reaction rate is severely limited by the slow CO₂ diffusion due to the absence of hydroxide that facilitates the CO₂ diffusion in an acidic environment. Here, we design an optimal architecture of a gas diffusion electrode (GDE) employing a copper-based ultrathin superhydrophobic macroporous layer, in which the CO₂ diffusion is highly enhanced. This GDE retains its applicability even under mechanical deformation conditions. The CO₂RR in acidic electrolytes exhibits a Faradaic efficiency of 87% with a partial current density \(( {j}_{{{{\rm{C}}}}_{2+}})\) $\left(j_{{\mathrm{C}}_{2+}}\right)$ of −1.6 A cm⁻² for multicarbon products (C₂₊), and \( {j}_{{{{{{\rm{C}}}}}}_{2+}}\) $j_{{\mathrm{C}}_{2+}}$ of −0.34 A cm⁻² when applying dilute 25% CO₂. In a highly acidic environment, C₂₊ formation occurs via a second order reaction which is controlled by both the catalyst and its hydroxide.