Gram-scale synthesis of carbon nitride via synergistic strategy of sulfur doping and ionic liquid compositing for superior photocatalytic hydrogen evolution from simulated seawater

In this work, a synergistic ionic liquid-incorporated sulfur-doped carbon nitride composite (S-C 3 N 4 /IL) was designed and synthesized via self-assembly at ambient conditions. The introduced sulfur dopants demonstrated dual functionalities: (i) mediating the interfacial compatibility between hydrophilic ionic liquids (ILs) and hydrophobic C 3 N 4 , and (ii) significantly enhancing electronic conductivity. Concurrently, the IL component was found to play critical roles in: (i) suppressing photoinduced charge recombination via enhanced electron transfer kinetics as evidenced by abundant free radicals according to electron paramagnetic resonance (EPR) spectra, and (ii) improved aqueous-phase wettability evidenced by reduced contact angles. Consequently, the S-C 3 N 4 /IL composite achieved a hydrogen evolution rate of 16.39 mmol g −1 h −1 in simulated seawater, significantly exceeding that of undoped C 3 N 4 of 0.64 mmol g −1 h −1 . This study presents a method for constructing a novel photosensitizer set for efficient photocatalytic hydrogen evolution.