Microwave‐Assisted Synthesis of Cobalt‐Based Selenides as Catalyst Precursors for the Alkaline Water Oxidation

Abstract

When used to promote the oxygen evolution reaction (OER), transition‐metal chalcogenides convert into oxyhydroxide/(hydr)oxide catalysts, the performance of which depends on the properties of the precursor. The present study aims to explore these effects for cobalt and cobalt–iron selenides (CoSe n and Co1Fe1Se n ) prepared using a simple microwave‐assisted method, in comparison to a reference material synthesized by high‐temperature reaction of CoO x H y with Se vapors. Physical characterization of the microwave‐synthesized CoSe n demonstrates their sheet‐like morphology and identifies Co3Se4 as the major phase, which is essentially completely transformed into CoOOH during the OER. The temperature during the microwave‐assisted CoSe n synthesis affects the crystallinity, the electrochemically active surface area, and thereby the performance of the resulting catalysts. Further improvements in the activity are achieved by combining cobalt with iron into a bimetallic Co1Fe1Se n precursor, which transforms in situ into a CoOOH + FeOOH composite and sustains the OER rate of 100 mA cm−2 (33 A g−1) at an overpotential of ≈ 0.31 and 0.26 V at 24 ± 2 and 80 ± 1 °C, respectively. Satisfactory stability of the Co1Fe1Se n ‐derived electrodes is demonstrated through a 4‐day‐long test at 80 ± 1 °C and 100 mA cm−2.