Crystalline Oxygen-Modified\nCarbon Nitride Photocatalyst\nwith Enhanced Internal Electric Field and Strong Resistance to Ionic\nInterference for Robust Seawater Splitting

Photocatalytic\nseawater splitting to produce clean hydrogen from\nnonpotable water using sunlight is a crucial endeavor. However, the\nscarcity of high-performance photocatalysts in the promising yet fledgling\nfield presents a formidable challenge. Herein, we successfully synthesized\na crystalline oxygen-modified carbon nitride (CCNO) polymeric semiconductor\nthat served as an effective photocatalyst for seawater splitting.\nComprehensive characterizations and theoretical calculations revealed\nthat nitrogen vacancies and bridging oxygen in the CCNO lattice acted\nas potent Lewis acid–base pairs, creating an enhanced built-in\nelectric field. This advancement significantly accelerated charge\ndynamics and bolstered resistance to ionic interference in seawater.\nConsequently, CCNO exhibited a robust photocatalytic H<sub>2</sub> evolution activity of 29.51 mmol g<sup>–1</sup> h<sup>–1</sup> in natural seawater, with an impressive apparent quantum efficiency\nof 66.86% under 420 nm monochromatic light. Seawater splitting for\nH<sub>2</sub> production reached 16.83 mmol g<sup>–1</sup> under\nnatural light irradiation for 3 h (9–12 o’clock), showcasing\nits great potential for practical applications. This work presents\nstrategies for developing a metal-free photocatalyst and elucidates\nits reaction mechanism in the seawater splitting process, laying the\nfoundation for scalable production of clean hydrogen.