Hydrophilic or Hydrophobic: Revealing the Role of an Ionic Liquid by an Interfacial Hydrogen Bond in an Aqueous Zinc Battery

Hydrogen evolution reaction (HER) on Zn-metal constrains the development of aqueous zinc batteries. Ionic liquid (IL) additives are proposed to isolate interfacial H₂O and suppress HER. However, whether the addition of either hydrophilic or hydrophobic ILs can effectively suppress HER seems "contradictory". Herein, although the disproportionation of hydrophilic/hydrophobic properties leads to an interfacial H₂O content difference, we demonstrate that both hydrophilic and hydrophobic ILs present a consistent influence on the configuration of interfacial hydrogen bonds. Specifically, they both decrease the amount of weak hydrogen bonds and increase the number of strong hydrogen bonds simultaneously, which makes the deprotonation of H₂O (related to HER) more difficult. In addition, by capturing the dynamic evolution of interfacial hydrogen bonds through in situ spectroscopy, we successfully correlate the evolution of interfacial hydrogen bonds with detrimental HER parasitic reaction on the Zn-metal surface. This study enhances the understanding of interface engineering from the perspective of interfacial hydrogen bond dynamic evolution.