posted on 2021-02-18, 21:33authored byAssel Amirzhanova, Nesibe Akmanşen, Irmak Karakaya, Ömer Dag
The
oxygen evolution reaction (OER) is the bottleneck of the electrochemical
water-splitting process, where the use of porous metal oxide electrodes
is beneficial. In this work, we introduce a one-pot synthesis method
to fabricate a series of mesoporous metal cobaltite (m-MCo2O4, M = Mn, Ni, and Zn) electrodes for the OER. The method
involves preparation and coating of a homogeneous clear solution of
all ingredients (metal salts and surfactants) over a fluorine-doped
tin oxide surface as a thin lyotropic liquid crystalline film and
calcination (as low as 250 °C) to obtain a 400 nm thick crystalline
m-MCo2O4 electrode with a spinel structure.
Mesophases and m-MCo2O4 films are characterized
using structural and electrochemical techniques. All electrodes are
stable during the electrochemical test in 1 M KOH aqueous solution
and perform at as low as 204 mV overpotential at 1 mA/cm2 current density; the m-MnCo2O4 electrode works
at current densities of 1, 10, and 100 mA/cm2 at 227, 300,
and 383 mV overpotentials after compensating the IR drop, respectively.
The Tafel slope is 60 mV/dec for the m-NiCo2O4 and m-ZnCo2O4 electrodes, but it gradually
increases to 85 mV/dec in the m-MnCo2O4 electrode
by thermal treatment, indicating a change in the OER mechanism.