Synergistic effect of quantum confinement and site-selective doping in polymeric carbon nitride towards overall water splitting

Photocatalytic overall water splitting is a challenging topic in the research field of solar energy conversion. Herein, we proposed an effective strategy of adopting quantum confinement effect and site-selective doping to realize simultaneous hydrogen and oxygen production from pure water over polymeric carbon nitride (CN) photocatalysts. Selectively doping P atoms in the corner-carbon sites provided efficient charge transfer channels between different structural units. Meanwhile, the site-selective P doping could generate mid-gap states below the conduction band of CN, which extended the utilization of visible light up to 600 nm, and served as trapping centres to inhibit the charge recombination. In addition, the quantum confinement effect could ensure the sufficient driving force for the rate-determining water oxidation. As a consequence, the hydrogen production rate from overall water splitting reached 619.5 μmol·h⁻¹ g⁻¹ under simulated sunlight irradiation, with notable apparent quantum yields of 6.8% at 400 nm and 2.4% at 500 nm.