Soft-template synthesis of sp2-carbon linked polymeric carbon nitride porous nanotubes with enhanced photocatalytic hydrogen evolution

Highlights: • The sp²-C linked polymeric carbon nitride (C-CN) porous nanotubes were prepared. • Polyethyleneimine was used as the template and modifying agent for C-CN synthesis. • The sp²-C introduced an impurity level in the bandgap of C-CN. • C-CN exhibits extended visible light absorption and enhanced charge separation. • C-CN exhibits wavelength-dependent enhancement in photocatalytic H₂ evolution. Morphological and structural modifications are effective ways to improve the photocatalytic performance of polymeric carbon nitride (CN), a promising photocatalyst for industrial application, but research on simultaneous morphological control and covalent bond insertion in CN and relevant structure-function relationships are still rare. Herein, sp²-carbon linked CN (C-CN) porous nanotubes were simply synthesized by first using polyethyleneimine as the template and modifying agent, and exhibit an enlarged specific surface area, enhanced visible light absorption and charge separation, originating from the sp²-C introduced impurity level in the bandgap, and thus improved photocatalytic H₂ evolution activity under visible light irradiation, compared with the bulk CN. Interestingly, the photoactivity of C-CN at wavelengths of 400 and 420 nm is lower than CN because of the sp²-C insertion induced reduction of amino groups which are active sites for H₂ evolution. That is, the photoactivity enhancement of C-CN is λ-dependent. This work elucidates the sp²-C linked structure-performance relationship of C-CN, and may direct future research on atom-linked mesoporous CN-based photocatalysts.