Construction of carbon nitride-based heterojunction as photocatalyst for peroxymonosulfate activation: Important role of carbon dots in enhancing photocatalytic activity

Strategic combination of carbon dots (CDs) and carbon nitride (CN) has provided an appealing strategy to synthesize metal-free carbonaceous catalyst for environmental-concerned photocatalytic applications. However, there still exists an ambiguous cognition on the relationship between functional structures of CDs and enhanced photocatalytic activity of CDs/CN composites. Herein, different types of functionalized CDs were physically integrated with CN matrix to construct CDs/CN heterojunctions. By systematically investigating the efficiency of CDs/CN-catalyzed peroxymonosulfate (PMS) in p-nitrophenol degradation, we revealed that the CDs enriched with carboxyl groups or doped by pyrrolic-N inclined to attract photogenerated electrons from CN host, and thus contributed to the photocarriers separation. As such, these CDs-imparted active sites can dramatically facilitate PMS activation, and further p-nitrophenol degradation by photogenerated holes and multiple reactive oxygen radicals. Nonetheless, the CDs mainly doped by electron-donating graphitic-N could form electron-rich regions at the interface of CN host upon forming heterojunction, thus making barriers against charge separation in the PMS-mediated oxidation process. Taken together, this study will shed light on the rational design of CDs/CN heterojunctions with high photocatalytic activity.