Chloride Ion-Induced Spatial Separation and Long Recombination Time of Photogenerated Electrons and Holes in Crystalline Carbon Nitride

Poly(triazine imide)·Li+Cl– (PTI/Li+Cl–) as one of the most reported crystalline carbon nitrides has shown exciting potential for photocatalysis. However, understanding the role of Li+/Cl– in the photoexcited charge transfer in the time and space of PTI is a challenging problem. Here, we have investigated the nonradiative charge recombination of series ion intercalated PTI systems (PTI/Li+X–, where X = F, Cl, Br, and I) by performing the ab initio nonadiabatic molecular dynamics simulations. The results indicate that the intercalated anions in PTI/Li+Cl– and PTI/Li+Br– have the potential to trap holes, separate the electrons and holes, and prolong the nonradiative electron–hole recombination. In particular, ∼70% of holes in PTI/Li+Cl– can transport among interlayers toward the {0001} planes, while most of the electrons are transferred to the {101̅0} planes, exhibiting different transport pathways and directions. Furthermore, PTI/Li+Cl– has an electron–hole recombination time as long as 136 ns, which explains its excellent optoelectronic properties. This work provides a theoretical baseline for the reported facet engineering improvement of crystalline carbon nitride for overall water splitting.