Rational Engineering of Self-Supported Catalysts for High-Performance Electrochemical Oxygen Evolution and Ethylene...

Development of efficient electrocatalyst materials for performing both the oxygen evolution reaction (OER) and the electrochemical oxidation of ethylene glycol (EGOR) is crucial for advancing energy-efficient electrolysis and valorization of plastic waste-derived chemicals. In this study, we present a comprehensive investigation of self-supported Ni-based catalysts grown on nickel foam and systematically tuned with Mn, Fe, Co, and Pd to achieve controllable bifunctional activity. Among these materials, Fe-NiO _x H _y exhibits superior OER performance in 1 M KOH, delivering an overpotential of 250 ± 7 mV at 100 mA cm^-2 with a Tafel slope of 35 ± 2 mV/dec. Hierarchical architectures and their crystal structure, confirmed by scanning electron microscopy and X-ray diffraction, provide abundant active sites and enhance mass transport kinetics. Quasi in situ Raman spectroscopy and ex situ X-ray photoelectron spectroscopy reveal potential, reactant concentration and activation-dependent reconstruction of metal active sites, demonstrating how controlled tuning of metal oxidation states affects both OER activity and EGOR selectivity. Electrochemical activation enhances the valence of metal centers, enabling precise control over EGOR product selectivity. Pd incorporation stabilizes *C₂ intermediates, favoring glycolate formation at low anodic potentials, while Mn-, Fe-, and Co-modified Ni promote a *C₁ pathway leading to formate at relatively higher potentials, with Fe-NiO _x H _y achieving a Faradaic efficiency (FE) of up to 86.2% toward formate. In contrast, Pd-NiO _x H _y /NF delivers a glycolate FE of up to 92.5%. Optimized reaction conditions, including applied potential, EG concentration, and activation protocol, allow selective production of either glycolate or formate during EGOR. This work provides an active site and mechanistic understanding connecting catalyst composition, activation, and oxidation-state dynamics to selectivity, providing a detailed insight for integrating PET-derived EG valorization with energy-efficient hydrogen production.