Tailoring aromatic ring-terminated edges of g-C3N4 nanosheets for efficient photocatalytic hydrogen evolution with simultaneous antibiotic removal

Abstract

Photocatalytic H₂ evolution with simultaneous organic removal by dual-functional photocatalytic systems is greatly limited by the weak visible-light absorbance and charge separation of these systems, especially the ready surface back-reaction of photogenerated electrons with radical intermediates. Herein, novel aromatic ring-terminated g-C₃N₄ nanosheets (ARCNSs) were prepared by a one-step copolymerization process by employing quinazoline-2,4-diamine as a molecular-structure-blocking and aromatic ring-terminated edge-directing agent. With the introduction of aromatic rings onto the edges of the g-C₃N₄ framework, the photocatalytic H₂ evolution with simultaneous antibiotic total organic carbon (TOC) removal was significantly enhanced. In particular, ARCNS-3 shows a H₂ evolution rate of 1021 μmol h⁻¹ g⁻¹ simultaneous with 92.1% TOC removal from tetracycline wastewater under visible-light irradiation, much higher than the values for pristine g-C₃N₄ nanosheets (H₂-evolution rate of 325 μmol h⁻¹ g⁻¹ simultaneous with 18% TOC removal). The considerably enhanced dual-functional photocatalytic activity ascribed to the aromatic rings on the edges of g-C₃N₄ could suppress the back-reaction between the radical intermediates and the photogenerated electrons, enlarge its surface area, extend its light-absorbance to 900 nm, and improve the charge separation at the same time. This work not only provides a promising route to enhance photocatalytic H₂ production with simultaneous organic pollutant removal but also provides new insight into the reaction control of dual-functional photocatalytic systems.