Overcoming Low C₂₊ Yield in Acidic CO₂ Electroreduction: Modulating Local Hydrophobicity for Enhanced Performance

Operating electrochemical CO₂ reduction reaction (CO₂RR) in acidic media has garnered considerable attention due to its sustainable electrolyte cycling and stable performance. Nevertheless, the severe parasitic hydrogen evolution reaction (HER) and decayed multi-carbon species (C₂₊) yield still hampers efficient CO₂RR in acid. Here, this work investigates the influence of local hydrophobicity on the acidic CO₂RR. By employing direct electrodeposition, the hydrophobicity of the catalyst layer can be finely tuned over a wide range without additive. It is revealed that the hydrophobic microenvironment significantly suppressed HER, improved CO₂RR performance and boosted C₂₊ yield. A Faradaic efficiency (FE) of ≈74% for C₂₊ is achieved in pH = 2 on electrodeposited copper with a highly hydrophobic environment. Moreover, this phenomenon can be extended to industrial application. An ≈81% total FE for the CO₂RR, along with a ≈62% FE for C₂₊ species, is achieved even with commercial copper. Remarkably, the system exhibited stable operation for a continuous period exceeding 50 h at an industrially applied current density of 300 mA cm^-2. This work highlights the crucial role of interface hydrophobicity in acidic CO₂RR and proposes a facile and universally applicable method for achieving efficient and stable CO₂RR to high-value products in acidic media.