Thin-film iron-oxide nanobeads as bifunctional electrocatalyst for high activity overall water splitting

Abstract

Developing only Fe derived bifunctional overall water splitting electrocatalyst both for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) while performing at low onset overpotential and with high catalytic stability is a rare instance. We present here the first demonstration of unique iron-oxide nanobeads (FeOx-NBs) based electrocatalyst executing both OER and HER with high activity. Thin-film electrocatalytic FeOx-NBs assembly is surface grown via simple spray coating (SC). The unique SC/FeOx-NBs propels OER initiating water oxidation just at 1.49 VRHE (η = 260 mV) that is the lowest observable onset potential for OER on simple Fe-oxide based catalytic films reported so far. Catalyst also reveals decently high HER activity and competent overall water splitting performance in the FeOx-NBs two-electrode system as well. Catalyst also presents stable kinetics, with promising high electrochemically active surface area (ECSA) of 1765 cm2, notable Tafel slopes of just 54 mV dec1− (OER) and 85 mV dec1− (HER), high exchange current density of 1.10 mA cm2− (OER), 0.58 mA cm2− (HER) and TOF of 74.29s1−@1.58VRHE, 262s1−@1.62VRHE (OER) and 82.5s1−@-0.45VRHE, 681s1−@-0.56VRHE (HER).