Overcoming Low C 2+ Yield in Acidic CO 2 Electroreduction: Modulating Local Hydrophobicity for Enhanced Performance.

Operating electrochemical CO2 reduction reaction (CO2 RR) 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 CO2 RR in acid. Here, this work investigates the influence of local hydrophobicity on the acidic CO2 RR. 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 CO2 RR 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 CO2 RR, 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 CO2 RR and proposes a facile and universally applicable method for achieving efficient and stable CO2 RR to high-value products in acidic media.