Melamine-phytic acid derived supramolecular synthesis of g-C3N4 for enhanced solar hydrogen evolution

It is an effective approach to regulate the structure of photocatalysts by introducing the heteroatoms into the lattice for extended light absorption and enhanced charge separation. In this work, the P atoms were introduced to substitute the corner C atoms of g-C3N4 by calcinating the melamine-phytic acid derived supramolecular with high-density phosphate groups, which is synthesized by hydrothermal method. The intermediate state produced by the introduction of P atoms leads to the enhanced light absorption of P–CN(7.2g-IP6) with a negative shifted conduction band position, which benefits the photocatalytic hydrogen reaction kinetically. Moreover, the electron transferred from P atom to the surrounding N atoms results in the positively charged P center, which could act as Lewis acid site. Such formed Lewis acid site at positively charged P center together with the Lewis base sites, such as amine or imine groups in P–CN, makes it easier to separate photogenerated charges, thus enabling the P–CN(7.2g-IP6) to exhibit an enhanced photocatalytic hydrogen rate of 2.743 mmol·g−1·h−1, which is about 6.77 times that of pristine g-C3N4 (0.405 mmol·g−1·h−1). This work provides an alternative approach to regulating the structure of photocatalysts.