Blocking Interfacial Proton Transport via Self‐Assembled Monolayer for Hydrogen Evolution‐Free Zinc Batteries

Abstract Aqueous Zn‐ion batteries (ZIBs) are promising next‐generation energy storage devices, yet suffer from the issues of hydrogen evolution reaction (HER) and intricate side reactions on the Zn anode surface. The hydrogen (H)‐bond networks play a critical role in interfacial proton transport that may closely relate to HER but are rarely investigated. Herein, we report a self‐assembled monolayer (SAM) strategy which is constructed by anchoring ionic liquid cations on Ti 3 C 2 T x substrate for HER‐free Zn anode. Molecule dynamics simulations reveal that the rationally designed SAM with a high coordination number of water molecules (25–27, 4–6 for Zn 2+ ) largely reduces the interfacial densities of H 2 O molecules, therefore breaking the connectivity of H‐bond networks and blocking proton transport on the interface, by which the HER is suppressed. Then, a series of in situ characterizations demonstrate that negligible amounts of H 2 gas are collected from the Zn@SAM‐MXene anode. Consequently, the symmetric cell enables a long‐cycling life of 3000 h at 1 mA cm −2 and 1000 h at 5 mA cm −2 . More significantly, the stable Zn@SAM‐MXene films are successfully used for coin full cells showing high‐capacity retention of over 94 % after 1000 cycles and large‐area (10×5 cm 2 ) pouch cells with desired performance.