Synergistic Doping and Surface Decoration of Carbon Nitride Macrostructures by Single Crystal Design

Tailored design of hybrid carbon nitride (CN) materials is quite challenging because of the drawbacks of the solid-state reaction, and the utilization of single crystals containing C-N monomers as reactants for the high-temperature reaction has been proven to imprint a given chemical composition, morphology, or electronic structure. We report the one-pot synthesis of alkali-containing CN macrostructures with ionic crystals on its surface by utilizing a tailored melamine-hydrochloride-based molecular single crystal containing NaCl and KCl as reactants. Structural and optical investigations reveal that upon calcination, molecular doping with Na⁺ and K⁺ is achieved, and additionally, the ionic species remain on the surface of the materials, resulting in an enhanced H₂ evolution performance through water splitting owing to a high ionic strength of the reaction media. Additionally, the most stable configuration of the alkaline metals in the CN lattice is evaluated by DFT calculations. This work provides an approach for the rational design of CN and other related metal-free materials with controllable properties for energy-related applications and devices.