Dual molecule-mediated polymerization for g-C₃N₄ photocatalysts toward efficient pollutant degradation and hydrogen...

Graphitic carbon nitride (g-C₃N₄) is readily accessible through thermal polycondensation of nitrogen-containing precursors, but its photocatalytic efficiency remains largely constrained due to a compactly stacked texture, small surface area, and rapid electron-hole recombination. Herein, loosely-textured g-C₃N₄ nanosheets were synthesized by thermal polymerization of the mixed melamine and urea precursors in the presence of structure-mediating oxalic acid and water molecules. This dual-molecule-mediation gave some enhanced features to g-C₃N₄, such as increased surface area, relatively high crystallinity, and negatively-shifted conduction band. Subsequently, ZnS-NiS₂ (ZNS) as a cocatalyst for improving photocatalytic hydrogen evolution was loaded on g-C₃N₄ nanosheets via solution phase deposition. The best performing g-C₃N₄ nanosheets (WOCN-0.1) exhibited a high removal efficiency of methyl orange (95.3 %), methylene blue (83.4 %), ciprofloxacin (73.9 %), and o-nitroaniline (98.3 %) within 90 min, respectively. Moreover, ZNS/WOCN-0.1 exhibited a high hydrogen evolution rate of 703.4 micromol h^-1 g^-1, showing an enhancement of 109 % in photocatalytic activity compared to ZNS/CN. The enhanced activity could be attributed to the improvement of charge separation and transfer, and easy hydrogen desorption. This work renders a potential of dual molecule-mediated polymerization in tuning the structures and catalytic performance of g-C₃N₄.