Quantitative Spectroscopic Analysis of Surface-Reaching Photoexcited Holes in g-CN/TiO Z-Scheme Heterojunctions.

The Z-scheme heterojunction has been demonstrated to be effective in tuning the photocatalytic performance of photocatalysts. However, there is still a lack of quantitative and in-depth research on how the Z-scheme heterojunction affects the concentration of surface-reaching photoexcited charges. Here, by combining time-resolved spectroscopies and kinetic analysis, the concentration of surface-reaching photoholes () within g-CN/TiO Z-scheme heterojunctions was quantitatively analyzed for the first time. Quantitative measurements reveal that of the prepared Z-scheme photocatalysts is highly dependent on the g-CN content and the induced Z-scheme heterojunctions at the g-CN/TiO interface. Encouragingly, we found that a properly engineered Z-scheme heterojunction with close coupling of g-CN and TiO can significantly increase the , leading to nearly a 1.7-fold increase compared with pristine TiO samples. Furthermore, a distinct hole trap state-mediated Z-scheme charge transfer mechanism was uncovered in which the intrinsic interface defects at the g-CN/TiO junction act as hole traps, accelerating interface electron-hole recombination, thereby boosting spatial charge separation and ultimately enriching the . This work provides insights into understanding and controlling electron pathways and in Z-scheme photocatalysis, with implications for the screening of different types of direct Z-scheme photocatalysts.