Cyanamide-Functionalized Carbon Nitride with Ion Modification for Enhanced “Dark” Photocatalysis

Abstract

Heterogeneous photocatalysis offers potential solutions for energy conversion, yet its effectiveness is compromised by the intermittent nature of solar energy. This research explores the “dark” photocatalysis, with a specific emphasis on the electron storing process in cyanamide-functionalized carbon nitride. In this study, cyanamide-functionalized carbon nitride with distinct ionic binding characteristics is synthesized. By tuning the ionic composition, an unprecedented electron storage capacity of 1.46 mmol g⁻¹ is attained postvisible light illumination, which is about 1.5 times greater than the previously reported carbon nitride materials. The electrons retained in carbon nitride demonstrate lifetimes of up to 10 days, and the efficiency of electron utilization during subsequent dark reactions ranges from 69% to >99%. Spectroscopic analysis reveals that ions significantly alter the electronic structure of the heptazine unit, affecting electron storage. Furthermore, it is demonstrated that stored electrons efficiently reduce aryl halides in the dark, demonstrating a robust photocharging–discharging process. The dehalogenation efficiency in the absence of illumination positively correlates with trapped charge accumulation in the carbon nitride framework, suggesting that charge storage enhances electron utilization. This research not only advances the understanding of electron storage in carbon nitride but also provides significant implications for the development of more efficient photocatalytic systems.