Potassium-Ion-Assisted Regeneration of Active Cyano Groups in Carbon Nitride Nanoribbons: Visible-Light-Driven Photocatalytic Nitrogen Reduction

As a metal-free nitrogen reduction reaction (NRR) photocatalyst, g-C₃N₄ is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g-C₃N₄-based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g-C₃N₄ photocatalyst modified with cyano groups and intercalated K⁺ (mCNN), possessing extended visible-light harvesting capacity and superior photocatalytic NRR activity (NH₃ yield: 3.42 mmol g⁻¹ h⁻¹). Experimental and theoretical studies suggest that the -C≡N in mCNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K⁺. The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst.