Efficient visible-light-driven photocatalytic hydrogen evolution and CO reduction over silver-modified tubular carbon nitride with enriched nitrogen vacancies.

Enhancing the photogenerated charge pairs separation efficiency is one of the most effective strategies to improve the performance of graphitic carbon nitride (g-CN) in photocatalytic hydrogen evolution and CO reduction. In this study, tubular g-CN (TCN) with a high specific surface area was synthesized via thermal polycondensation-self-assembly, followed by the uniform deposition of Ag nanoparticles on the TCN surface to construct heterojunctions. During the reduction of Ag, a higher level of nitrogen vacancies was introduced on TCN, which not only enhanced the delocalization of electrons but also provided additional active sites for photocatalytic reactions. Performance evaluations reveals that the 1 % Ag/TCN sample exhibits the highest visible-light-driven hydrogen evolution efficiency, up to 2667 μmol g·h, with an apparent quantum yield (AQY) of 7.12 % under 420 nm monochromatic light irradiation. Furthermore, all modified samples demonstrate superior performance in photocatalytic CO reduction, with the 1 % Ag/TCN sample achieving a CO evolution rate of 45.6 μmol g, which is 5.18 times than that of the pristine TCN sample. This "structure-interface-defect" cooperative multi-scale optimization strategy significantly enhanced the photogenerated charge carriers separation and migration rates of g-CN, thereby improving the photocatalytic performance. This integrated approach provides a reliable and cost-effective pathway to address the inherent limitations of semiconductor-based photocatalysts.