Synergistic Effect of Cobalt and Iron in Layered Double Hydroxide Catalysts for the Oxygen Evolution Reaction

Abstract

Co-based layered double hydroxide (LDH) catalysts with Fe and Al contents in the range of 15 to 45 at % were synthesized by an efficient coprecipitation method. In these catalysts, Fe³⁺ or Al³⁺ ions play an essential role as trivalent species to stabilize the LDH structure. The obtained catalysts were characterized by a comprehensive combination of surface- and bulk-sensitive techniques and were evaluated for the oxygen evolution reaction (OER) on rotating disk electrodes. The OER activity decreased upon increasing the Al content for the Co- and Al-based LDH catalysts, whereas a synergistic effect in Co- and Fe-based LDHs was observed, which resulted in an optimal Fe content of 35 at %. This catalyst was spray-coated on Ni foam electrodes and showed very good stability in a flow-through cell with a potential of approximately 1.53 V at 10 mA cm^-2 in 1 m KOH for at least 48 h.

Keywords: cobalt; iron; layered double hydroxides; oxygen evolution reaction; stability.