Iridium oxide-nickel-coated titanium anodes for the oxygen evolution reaction

Abstract

IrO2-Ni-modified Ti electrodes have been prepared by a Ni-mediated galvanic replacement method. A smooth Ni film has been electrodeposited on the Ti substrate from a Watts bath and its surface layers spontaneously exchanged with metallic Ir upon treatment with an Ir(IV) solution. Anodization of the resulting Ir(Ni)/Ti electrodes by means of continuous potential cycling in acid solutions resulted in the formation of porous IrO2 coatings showing typical Ir oxide/hydroxide surface electrochemistry. SEM pictures revealed that the thus prepared IrO2/Ir(Ni)/Ti electrodes consisted of continuous films with a nodular morphology (as confirmed by AFM). The composition of the coatings was estimated by EDS and XPS spectroscopy while the Ir mass loading was determined by ICP-MS following etching in acid. These electrodes have been tested as oxygen evolution reaction (OER) anodes by slow potential sweep voltammetry and were proven comparable or better than state-of-the-art thin thermal film and nanoparticulate IrNiOx-based electrodes (exhibiting ca 2 A mgIr−1 at η=300 mV). The recently established enhancement of IrO2 OER activity by Ni, combined with the widespread use of Ti as a stable electrode substrate, make IrO2/Ir(Ni)/Ti attractive candidates for Dimensionally Stable Electrodes (DSAs).