Enhanced photocatalytic H2 production independent of exciton dissociation in crystalline carbon nitride

The role of exciton dissociation in charge separation dominated by in-plane crystallinity has been rarely addressed, although it is the decisive step of polymeric carbon nitride (CN) photocatalysis. Here, taking ten kinds of crystalline carbon nitride (CCN) as examples, the relationship between exciton dissociation, carrier mobility, conductivity, charge separation and photocatalytic activity under different in-plane crystallinity has been investigated. Although the in-plane crystallinity dominates charge separation and photocatalytic activity, it does not significantly reduce excitons binding energy (EBE) or improve exciton dissociation efficiency (EDE), only decreasing by 1.5 meV and increasing by 2.3 %, respectively. It is the greatly improved carrier mobility and conductivity that are more responsible for the increased charge separation and photocatalytic activity than the slight change in EDE. To our knowledge, this is the first reported case of overall water splitting in CCN of poly (heptazine imide) structure, resulting from the optimized in-plane crystallinity.

Automated summary

The role of exciton dissociation in charge separation dominated by in-plane crystallinity was rarely studied in polymeric carbon nitride (CN) photocatalysis. In this study, the relationship between exciton dissociation, carrier mobility, conductivity, charge separation, and photocatalytic activity was investigated using ten types of crystalline carbon nitride (CCN) with different in-plane crystallinity. It was found that the improved carrier mobility and conductivity were more responsible for the increased charge separation and photocatalytic activity than the slight change in exciton dissociation efficiency (EDE). This study also reported the first case of overall water splitting in CCN of poly (heptazine imide) structure, resulting from optimized in-plane crystallinity.