Cobalt diselenide (001) surface with short-range Co–Co interaction triggering high-performance electrocatalytic oxygen evolution

Oxygen evolution reaction (OER) still suffers from the bottleneck in electrocatalytic water splitting. Herein, in virtue of volcano plots drawn by theoretical calculation, the (001) facet was screened as the superb facet of orthorhombic CoSe₂ for OER. Afterwards, CoSe₂(001) nanosheets were synthesized and the exposure ratio of (001) facet is controllable with thermodynamics methods effectively. The single-facet CoSe₂(001) delivered an overpotential as low as 240 mV at 10 mA·cm⁻² in 1 M KOH, which outperformed the bulk (380 mV) as well as other CoSe₂-base OER catalysts reported before. Especially, a shorter Co–Co path was observed in CoSe₂(001) by X­ray absorption spectroscopy. Further density functional theory (DFT) studies revealed that the reversible compression on the shorter Co–Co path could regulate the electronic structure of active sites during the OER process, and thus the energy barrier of the rate-determining step was reduced by 0.15 eV. This work could inspire more insights on the modification of electronic structure for OER electrocatalysts.