Reductive Electrodeposition of Cationic Polymer Networks for Conformal Permselective Interphases

Abstract The integration of ultrathin and conformal interphases onto electrodes can lead to advanced electrochemical systems with control over the near-surface nanoenvironment impacting the double layer, electrode stability, reagent access, and solvation. However, the precise fabrication of nanometric interphases with tailored thickness and composition without blocking active surface sites is challenging, especially on porous application-relevant electrodes. Here, we report the reductive and self-limiting electrodeposition of polymer networks (EPoN) as a versatile and tunable method to uniformly coat non-planar and porous electrodes with physically adhered ultrathin functional polymer networks. The deposition chemistry is based on cathodically mediated methylpyridinium crosslinking and achieves the fabrication of polymer thin films on oxidation-sensitive catalytic metals. Our reductive EPoN process follows a self-limiting growth mechanism, yielding uniform and defect-correcting coatings with tunable nanometric thickness and charge density. The polymer network interphase is permselective, retaining molecular access to the functional surface, but modulates its permeation and activity based on charge and size, as demonstrated with a positively charged nanometric interphase as a functional barrier for regulating the hydrogen evolution reaction on copper. Our reductive EPoN strategy establishes a robust platform to tailor catalytic interphases for precise control over the electrochemical nanoenvironment.