The oxygen evolution reaction (OER) is the bottleneck in the electrochemical splitting of water into hydrogen gas fuel and oxygen. Efficient and affordable catalysts must be developed to accelerate this reaction. Here we present the improved OER catalytic activity of cobalt oxide (CoOx) with the help of Fe3+ ions, and the mechanism behind. CoOx is electrodeposited onto glassy carbon working electrodes, while Fe3+ ions are added to the 1 M KOH electrolyte. The as deposited cobalt oxide catalyst exists in a capsular-like morphology with a lateral size of ~ 20 nm, and is confirmed to be amorphous Co3O4 with Co(OH)2 on the surface. The addition of Fe3+ ions into the 1 M KOH electrolyte leads to a significant enhancement in the OER performance of the cobalt oxide catalyst by lowering its overpotential (η) at 10 mA/cm2 from 374.0 ± 4.5 to 316.1 ± 2.3 mV. The Tafel slope also decreases from 57.7 ± 7.6 to 26.9 ± 0.4 mV/dec, and the stability of the CoOx catalyst is also improved. A salt bridge is introduced in to separate the cathodic compartment from the possible negative impact of Fe3+ ions and the Faradaic efficiency (FE) of hydrogen evolution reaction (HER) is confirmed to be &gt; 97%. The overall water splitting reaction can work at 10 mA/cm2 (in terms of OER) for more than 2 days with an overall applied potential of &lt; 1.7 V. The synergistic effect between cobalt and iron atoms towards OER is studied in situ by cyclic voltammetry (CV) and X-ray absorption spectroscopy (XAS). Both CV and in situ XAS experiments show that Fe atoms are electronically affected by the Co atoms. This finding is consistent with the assumption that Fe atoms are the main OER active sites in this CoOx + Fe catalytic system.

Electrodeposited cobalt oxide catalyst in Fe-spiked KOH electrolyte for efficient evolution of oxygen

253rd National Meeting (2017)

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