Carrier dynamics tailored by electron/hole trapping domains in asymmetric graphitic carbon nitride for superior photocatalytic hydrogen evolution

Abstract

Photocatalytic hydrogen production from water using solar energy represents a promising pathway for energy-intensive societies to overcome sustainability bottlenecks. However, the design and controllable synthesis of photocatalytic materials with high performance, high stability, and environmental compatibility remain challenging. The localized electronic structures and strongly bound Frenkel excitons in metal-free graphitic carbon nitride (g-C3N4) result in poor photocatalytic performance. To address these limitations, this work employs Density Functional Theory (DFT) calculations to guide the design and synthesis of g-C3N4 photocatalytic materials (EHTD-CN). Specifically, the integration of spatially separated electron-trapping and hole-trapping domains (ETD and HTD) alters the distribution of electron density. This creates a robust built-in electric field (BIEF) within symmetry-breaking conjugated frameworks, reducing the exciton binding energy and promoting photoexciton dissociation and subsequent migration to predetermined sites. Consequently, the proton reduction kinetics are accelerated. As a result, the synthesized EHTD-CN exhibits a significantly enhanced hydrogen production rate of 3.09 mmol g-1 h-1, which is 30.9-fold higher than that of bulk g-C3N4. Importantly, the underlying mechanisms of improved exciton dissociation and charge dynamics by the tailored electronic structure are thoroughly characterized and elucidated. This work provides new insights into DFT-guided photocatalytic material design for energy and environmental applications.