Engineering in-plane π-conjugated structures in ultrathin g-C₃N₄ nanosheets for enhanced photocatalytic reduction performance

In this study, an energetic materials (EM) deflagration process coupled with a gas-shocking exfoliation strategy was proposed for the in-situ introduction of a π-electron-conjugated structure into ultrathin g-C₃N₄ nanosheets. The optimal 2C-CNS sample was endowed with a porous-ultrathin-nanosheets morphology (3–4 nm thickness), larger exposed surface area (144.1 m²/g), and significant pore volume (0.51 cm³/g). Using urotropin-deflagration and gas-shocking-driven processes, the precursors were dissociated and copolymerized in an aqueous solution into g-C₃N₄ nanosheets chemically modified with conjugated carbon moieties. Most importantly, an expanded π-electron conjugated system was successfully constructed between the carbon moieties that interacted with the ultrathin g-C₃N₄ (2C-CNS), which endowed its with a faster electron-hole separation efficiency and enhanced visible-light harvesting ability. The H₂ evolution rate and Cr⁶⁺ reduction efficiency for 2C-CNS reached 2360 μmol h⁻¹ g⁻¹ for k = 0.0301 min⁻¹, which was almost 25.8/23 times higher than that of bulk g-C₃N₄ (Bu-CN, 91.2 μmol h⁻¹ g⁻¹, k = 0.0013 min⁻¹). Also, 2C-CNS showed 2.8/2.4 times higher performance than the g-C₃N₄ ultrathin nanosheets without a carbon-section modification (0C-CNS, 853 μmol h⁻¹ g⁻¹, k = 0.0125 min⁻¹).