单原子Co修饰TiO2(101)面的结构和析氢性能的第一性原理研究

通过基于密度泛函理论（DFT）+U的第一性原理方法研究了单原子Co在TiO₂（101）面的掺杂位置和方式、几何结构和整体能量以及掺杂后产物的制氢反应机制，得到了稳定且易出现的单原子修饰结构，即单原子Co吸附在4个O组成的表面空隙的中心位，记为Co/TiO₂（101）。进一步对Co/TiO₂（101）的析氢反应过程和性能进行研究，确定了当且仅当TiO₂（101）面完成表面羟基化反应后，H原子全覆盖的TiO₂（101）表面才能进行后续的析氢反应；此时单原子Co是唯一的反应位点，整体的制氢反应自由能ΔG_H*比Co（111）面更加趋近于0，显示出其具有远优于金属Co的催化性能。此外，Co和TiO₂间的电荷转移和相互作用使TiO₂带隙出现新的掺杂能级，可带来作为光催化基材的TiO₂光吸收性能的改善。

First principles calculations of the structure and hydrogen reaction performance of a single Co atom decorated-TiO2(101) surface

We have used the first principles method, the density functional theory (DFT)+U method to study the geometric structures, energies and hydrogen production reaction and reaction mechanism of a single Co atom doped onto a TiO₂(101) surface, and obtain a stable and facile single-atom decorated configuration involving a single Co atom on the hollow site of a surface interstice, which consists of four surface O atoms. Furthermore, we studied the associated hydrogen evolution reaction (HER) process and performance, and found that after the surface hydroxylation, HER can be carried out on the TiO₂(101) surface. The single atom Co is the only reaction site, and the free energies of the HER are closer to zero than in the case of Co(111), showing that the site has superior catalytic performance. Moreover, the charge transfer and interaction between Co and TiO₂ induce gap-doped states (energy levels), which results in the enhancement of light absorption by the photocatalyst substrate, TiO₂.