Reconstructing Supramolecular Aggregates to Nitrogen-Deficient g-C3N4 Bunchy Tubes with Enhanced Photocatalysis for H2 Production.

Developing a facile method to overcome the intrinsic shortcomings of g-C3N4 photocatalyst concerning its insufficient visible light absorption and dissatisfactory separation efficiency of charge carriers is of great significance but remains a challenge. In this work, we report, for the first time, a sapiential strategy for preparing highly efficient nitrogen-deficient g-C3N4 featuring bunchy microtubes [R-tubular carbon nitride (TCN)] via a KOH-assisted hydrothermal treatment of rodlike melamine-cyanuric acid (RMCA) supramolecular aggregates followed by heating the reconstructed RMCA, in which KOH serves as an all-rounder for breaking hydrogen bonds, accelerating hydrolysis of melamine and nitrogen defects forming. This approach endows R-TCN with unique bunchy microtube morphology, enriched nitrogen defects, textural properties, and electronic structure, which result in narrower band gap, higher electric conductivity, more active sites, more negative conductive band, significantly increased visible light harvesting capability, and improved separation efficiency of charge carriers. As a consequence, R-TCN shows 2.44 and 39 times higher hydrogen evolution rate (8.19 μmol h-1) than that of the pristine TCN from RMCA and bulk g-C3N4 from melamine. This new discovery may open a new avenue to fabricate highly efficient g-C3N4 catalysts.