Low Overpotential
in Vacancy-Rich Ultrathin CoSe<sub>2</sub> Nanosheets for Water Oxidation
- Publication date
- Publisher
Abstract
According
to Yang Shao-Horn’s principle, CoSe<sub>2</sub> is a promising
candidate as an efficient, affordable, and sustainable
alternative electrocatalyst for the oxygen evolution reaction, owing
to its well-suited electronic configuration of Co ions. However, the
catalytic efficiency of pure CoSe<sub>2</sub> is still far below what
is expected, because of its poor active site exposure yield. Herein,
we successfully overcome the disadvantage of insufficient active sites
in bulk CoSe<sub>2</sub> by reducing its thickness into the atomic
scale rather than any additional modification (such as doping or hybridizing
with graphene or noble metals). The positron annihilation spectrometry
and XAFS spectra provide clear evidence that a large number of V<sub>Co</sub>″ vacancies formed in the ultrathin nanosheets. The
first-principles calculations reveal that these V<sub>Co</sub>″
vacancies can serve as active sites to efficiently catalyze the oxygen
evolution reaction, manifesting an OER overpotential as low as 0.32
V at 10 mA cm<sup>–2</sup> in pH 13 medium, which is superior
to the values for its bulk counterparts as well as those for the most
reported Co-based electrocatalysts. Considering the outstanding performance
of the simple, unmodified ultrathin CoSe<sub>2</sub> nanosheets as
the only catalyst, further improvement of the catalytic activity is
expected when various strategies of doping or hybridizing are used.
These results not only demonstrate the potential of a notable, affordable,
and earth-abundant water oxidation electrocatalyst based on ultrathin
CoSe<sub>2</sub> nanosheets but also open up a promising avenue into
the exploration of excellent active and durable catalysts toward replacing
noble metals for oxygen electrocatalysis