posted on 2021-05-13, 16:08authored byFilipa
M. Oliveira, Jan Paštika, Vlastimil Mazánek, Manuel Melle-Franco, Zdeněk Sofer, Rui Gusmão
Two-dimensional
(2D) layered materials are currently one of the
most explored materials for developing efficient and stable electrocatalysts
in energy conversion applications. Some of the 2D metal phosphorous
trichalcogenides (M2P2X6 or MPX3 in its simplified form) have been reported to be useful catalysts
for water splitting, although results have been less promising for
the sluggish oxygen evolution reaction (OER) due to insufficient activity
or compromised stability. Herein, we report the OER catalysis of a
series of M2P2X6 (M2+ =
Mn, Fe, Co, Zn, Cd; X = S, Se). From the series of MPX3, CoPS3 yields the best results with an overpotential
within the range of values usually obtained for IrO2 or
RuO2 catalysts. The liquid-phase exfoliation of CoPS3 even improves the OER activity due to abundant active edges
of the downsized sheets, accompanied by the presence of surface oxides.
The influence of the OER medium and underlying substrate electrode
is studied, with the exfoliated CoPS3 reaching the lowest
overpotential at 234 mV at a current density of 10 mA/cm2, also able to sustain high current densities, with an overpotential
of 388 mV at a current density of 100 mA/cm2, and excellent
stability after multiple cycles or long-term operation. Quantum chemical
models reveal that these observations are likely tied to moieties
on CoPS3 edges, which are responsible for low overpotentials
through a two-site mechanism. The OER performance of exfoliated CoPS3 reported herein yields competitive values compared to those
reported for other Co-based and MPX3 in the literature,
thus holding substantial promise for use as an efficient material
for the anodic water-splitting reaction.