Light-Driven Trap Engineering in Direct Z-Scheme Channels for Ultrafast N ₂ Fixation

Employing density functional theory (DFT) combined nonadiabatic molecular dynamics (NAMD), we revealed that the shallow charge trap states, induced by Se vacancy and B atom doping strategies, regulate the transport mode and velocity of photoexcited carriers within the C₇N₆/MoSe₂ heterojunction. The rapid capture-release mechanism introduced by shallow trap states accelerates the interlayer recombination of weak carriers, reducing the lifetime from 22.37 ps to 1.35-1.62 ps and thereby minimizing the recombination-induced loss of highly active carriers. Real-time time-dependent DFT (RT-TDDFT) demonstrates that photogenerated electrons activate inert N₂ within 55 fs, preceding carrier deactivation. Boron dopants further facilitate N₂ fixation via the "acceptance-donation" mechanism, achieving a remarkably low limiting potential of -0.23 V and significantly improving NH₃ selectivity. This study modulates charge migration and recombination channels in the Z-scheme heterojunction through loading and defect strategies to enhance carrier redox capabilities, providing an alternative perspective for achieving photocatalytic N₂ fixation under ambient conditions.