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

Abstract Operating electrochemical CO 2 reduction reaction (CO 2 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 (C 2+ ) yield still hampers efficient CO 2 RR in acid. Here, this work investigates the influence of local hydrophobicity on the acidic CO 2 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 CO 2 RR performance and boosted C 2+ yield. A Faradaic efficiency (FE) of ≈74% for C 2+ 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 CO 2 RR, along with a ≈62% FE for C 2+ 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 CO 2 RR and proposes a facile and universally applicable method for achieving efficient and stable CO 2 RR to high‐value products in acidic media.