Modulation of Carbon Nitride Using Supramolecular Self-Assembly for Facilitating Photocatalytic Seawater Hydrogen Production

Solar-driven photocatalytic seawater splitting for hydrogen production represents a crucial green technology pathway for achieving a sustainable energy supply. In this study, a series of tremella-like porous graphitic carbon nitride photocatalysts (CNC- x ) were constructed via a supramolecular self-assembly strategy to enhance the photocatalytic hydrogen evolution from seawater. The optimized CNC-1.4 achieved a hydrogen evolution rate of 4.7 mmol·g –1 ·h –1 in natural seawater containing triethanolamine (TEOA) under visible-light irradiation, which is nearly 20 times higher than that of bulk g-C 3 N 4 (0.23 mmol·g –1 ·h –1 ). Moreover, under natural sunlight (10:00–16:00), CNC-1.4 maintained a hydrogen evolution rate of approximately 4.9 mmol·g –1 ·h –1 and exhibited excellent cycling stability. These results demonstrate good seawater tolerance during sacrificial-agent-assisted hydrogen evolution and highlight the promising potential for practical solar-driven hydrogen production in seawater. Finally, by systematically comparing the photocatalytic performance in pure water, artificial seawater, and natural seawater under sacrificial-agent-free conditions, we further confirmed that only in the presence of TEOA can the system achieve efficient hydrogen evolution in seawater while effectively suppressing the associated side reactions. This study provides a new design strategy for constructing efficient g-C 3 N 4 based photocatalytic systems and lays an essential foundation for practical solar-powered direct hydrogen production from seawater.