Evaluation of iron oxide coatings as electrocatalysts for oxygen evolution reaction obtained via electrodeposition and magnetron sputtering

In this work, the electrocatalytic activity of hematite with a porous and compact structure was investigated in the process of oxygen evolution. Porous coatings were synthesized using potentiodynamic ElectroDeposition (ED) and thermal treatment, while compact coatings were synthesized by Magnetron Sputtering (MS). Electrocatalytic evaluation of the coatings showed that there is no significant difference with respect to the overpotential of the reaction onset potential, which is 342-353 mV for electrodeposited samples and 341-355 mV for those obtained by the MS method. However, the advantage of compact coatings has emerged at higher current density values, when the activity of porous coatings faces limitations due to diffusion from and into the pores. Calculations of the coefficient b of the Tafel equation revealed the superiority of porous structures (avg. 48 mV center dot dec-1) at the beginning of the reaction over compact coatings (avg. 56 mV center dot dec-1).