Electrochemically Aged Ni Electrodes Supporting NiFe2O4 Nanoparticles for the Oxygen Evolution Reaction
Abstract
The preparation and screening of nanoparticle (NP) electrocatalysts for improved electrocatalytic oxygen evolution reactions (OER) will require a better understanding and optimization of the interactions between NPs and their support. First-row transition metals are used extensively as electrocatalysts in electrochemical energy storage and conversion systems. These electrocatalysts undergo transformations in their phase and surface morphology, which are induced by oxidizing potentials in the alkaline medium. A template-assisted approach to prepare electrodes with regular surface morphologies was used to monitor interactions between the NPs and their support both before and after prolonged electrochemical aging. A template-assisted method was used to prepare uniform surface inclusions of nickel ferrite (NiFe2O4) NPs on conductive nickel (Ni) supports for evaluation toward the OER. Electron microscopy-based methods were used to assess the resulting transformations of the embedded NPs within the Ni support matrix. Electrochemical aging of these textured electrodes was conducted by cyclic voltammetry (CV) techniques, which resulted in the growth of a 200 nm thick Ni oxy(hydroxide) film on the surfaces of the Ni supports. The growth of the active surface layer led to the encapsulation of the NiFe2O4 NPs as determined by correlative energy dispersive X-ray spectroscopy (EDS) techniques. The NP-modified electrodes exhibited reduced overpotentials and higher sustained current densities for the OER when compared to pure Ni supports. The well-defined morphologies and NP surface inclusions prepared by the template-assisted approach could serve as a platform for investigating additional NP-support interactions for electrocatalytic systems.