Electropolymerization Turns an Inactive Molecular Complex into a Water Oxidation Catalyst

Abstract

Abstract Understanding how structure gives rise to function lies at the heart of catalysis. Yet one of the most fundamental open questions is whether catalytic activity can emerge purely from connectivity, without altering the composition or coordination of the molecular building blocks. Here, we demonstrate that in situ electropolymerization of Fe-phthalocyanine, a complex completely inert toward oxygen evolution at neutral pH, creates catalytic function where none existed before. The polymerized films exhibit strong and stable oxygen evolution activity under both electrochemical and photoelectrochemical conditions, in sharp contrast to the electro-inactive monomeric or drop-cast forms. Using scanning electrochemical microscopy (SECM), and conductive atomic force microscopy (CAFM), we independently visualize spatial heterogeneity in both catalytic activity and electronic conductivity across the polymeric film. In situ Raman spectroscopy captures the evolution of Fe-oxo and epoxide-like intermediates during operation; these features are plausibly assigned to key OER intermediates, supporting the coexistence of multiple catalytic motifs, revealing vibrational features strongly consistent with active-site formation within the evolving network. Complementary density functional theory calculations reveal that polymerization drives electronic delocalization and Fe–Fe orbital coupling, stabilizing O–O bond-forming intermediates and lowering the overall reaction barrier. Together, these findings show that polymerization is not a passive structural event but an active mechanistic trigger that redefines how charge flows, intermediates stabilize, and reactivity emerges. This study introduces a general framework in which catalysis can arise from electronic and topological reorganization, turning molecularly inert systems into active catalysts through the deliberate creation of conductive, redox-cooperative architectures.