Electrodeposited Cobalt Bis(pyridylimino)isoindolide Complex on Graphite: Synthesis, Characterization, and Electrocatalytic Activity Toward Hydrogen Evolution Reaction

Abstract

Electrodeposited cobalt bis(pyridylimino)isoindolide (BPI) complexes on graphite combine the favorable coordination chemistry of the BPI framework with the excellent electrical conductivity and surface properties of graphite. Their tunable ligand environment allows for precise control over the metal's electronic structure, enhancing proton reduction kinetics. Furthermore, strong π–π interactions between the pyrene substituents and the graphitic surface promote robust adhesion and an extended active interface, making these materials attractive candidates for durable, high-performance electrocatalysts. In this work, we report the synthesis and full characterization of a novel pyrene-substituted BPI ligand and its corresponding cobalt complex. These BPI derivatives were electrodeposited onto a graphite substrate by cyclic voltammetry, and the resulting modified electrodes were evaluated for their hydrogen evolution reaction (HER) performance. Morphological, structural, and spectroscopic analyses, including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), provided detailed insight into the surface structure and composition of the electrodeposited films. Electrochemical impedance spectroscopy (EIS) highlighted the effective charge–transfer properties and double-layer capacitance of the cobalt BPI coatings. A comparative analysis of the electrochemical data with the structural findings confirmed that the electrodeposited cobalt BPI complexes form uniform, conductive layers on graphite, exhibiting promising catalytic activity for hydrogen evolution.