Effects of Morphology on Nanostructured Cobalt Oxides for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is important process in water-splitting electrochemical devices for oxidation of water to molecular oxygen [1-4]. In particular, OER is the most important reaction process because the overall cell efficiency depends strongly on the reaction rate of the OER.  Until now, noble metal catalysts such as iridium, ruthenium, and platinum have shown excellent performances for the OER and even ORR in fuel cell conditions [5]. However, these noble metal catalysts have disadvantage for making commercialization of such electrochemical devices in terms of high cost and limited durability [6, 7].

In order to cope with these issues, in this work, various transition metal oxides such as manganese oxides and cobalt oxides are investigated for replacing expensive noble metals of water-splitting electrochemical cells with enhanced durability [8, 9]. To achieve high efficient electrocatalyst for OER, in addition, various nanostructured metal oxide catalysts are synthesized by the hydrothermal method using nitrate or acetate-based precursors [10].

Synthesized catalysts are physicochemically characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). For analysis of electrochemical properties, cyclic voltammetry (CV) and OER are measured by rotating disk electrode (RDE) system. A Pt wire and Ag/AgCl electrode are used as a counter electrode and a reference electrode in 0.1 M KOH electrolyte. OER activity is measured by the linear sweep voltammetry (LSV) from  1.2 to 1.7 V at a scan rate of 5 mV s^-1 to compare each nanostructured transition metal oxide powders.

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 * Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park).