Coordination Tuning in Cobalt Selenites for Electrocatalytic Water Oxidation

Cobalt-based materials have been considered as the most
promising
cheap electrocatalysts for water oxidation. The coordination structure
of Co affects the catalytic performance significantly. However, the
internal causes remain elusive because of the lack of rational design
of Co-based materials with clear and singular coordination geometry.
Herein, two crystalline cobalt selenites were designed with isolated
octahedral or tetrahedral Co centers. It was found that the intrinsically
better performance of the octahedral Co site originated from its splitting
energy of the 3d orbitals. This splitting accounts for the faster
construction of CoIV species, the higher concentration
of CoIV species, and the stronger oxidative ability of
CoIV species in the selenite with octahedral Co sites.
Therefore, how the coordination structure of Co centers regulates
the water oxidation performance was revealed in a straightforward
manner based on the designed analogous selenites.