Oxygen vacancy (O_v) as well as O_v migration in metal oxide are of great importance in structural evolution of active center in single-atom catalysts (SACs). Here, the interplay between invasive single Pt atom and native O_v in SA-Pt/rutile TiO₂(110) surface, as well as their synergetic effect on water dissociation are investigated by density functional theory (DFT) calculations. We show that importing Pt atom as Pt-ads, Pt_2c, Pt_5c and Pt_6c modes could decelerate the O_v migration effectively, especially in Pt_6c mode. Under oxygen-rich conditions, Pt_6c substitution could make oxygen O_v formation easier, but migration harder. On Pt_6c/Ti_1-yO_2-x1(110) surface, as a bimetal center, Pt_4c-Ti_5c concave could not make water dissociation process easier; however, the O_2c closed to Pt become a good proton acceptor to make water dissociation on Ti_5c-O_2c more convenient with the aid of topmost Ti_5c.

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.