Promoted surface charge density from interlayer Zn–N4 configuration in carbon nitride for enhanced CO2 photoreduction

The solar-driven reduction of CO2 into valuable products is a promising method to alleviate global environmental problems and energy crises. However, the low surface charge density limits the photocatalytic conversion performance of CO2. Herein, a polymeric carbon nitride (PCN) photocatalyst with Zn single atoms (Zn1/CN) was designed and synthesized for CO2 photoreduction. The results of the CO2 photoreduction studies show that the CO and CH4 yields of Zn1/CN increased fivefold, reaching 76.9 and 22.9 µmol/(g·h), respectively, in contrast to the unmodified PCN. Ar+ plasma-etched X-ray photoelectron spectroscopy and synchrotron radiation-based X-ray absorption fine structure results reveal that Zn single atom is mainly present in the interlayer space of PCN in the Zn–N4 configuration. Photoelectrochemical characterizations indicate that the interlayer Zn–N4 configuration can amplify light absorption and establish an interlayer charge transfer channel. Light-assisted Kelvin probe force microscopy confirms that more photogenerated electrons are delivered to the catalyst surface through interlayer Zn–N4 configuration, which increases its surface charge density. Further, in-situ infrared spectroscopy combined with density functional theory calculation reveals that promoted surface charge density accelerates key intermediates (⋆COOH) conversion, thus achieving efficient CO2 conversion. This work elucidates the role of internal single atoms in catalytic surface reactions, which provides important implications for the design of single-atom catalysts.