Salt-assisted synthesis of 3D open porous g-C3N4 decorated with cyano groups for photocatalytic hydrogen evolution

Abstract

Three-dimensional open porous graphitic carbon nitride with cyano groups (3D OPG-C₃N₄-CN) has been fabricated by a facile two-step process that combines NaCl-assisted freeze-drying with calcination. NaCl not only works as a template for the 3D open porous structure, but also facilitates the decomposition of g-C₃N₄ around 500 °C to some extent. Meanwhile, a moderate amount of cyano groups acting as electron capture centers are introduced at the edge of the 3D open porous g-C₃N₄ during the formation process. Compared with bulk g-C₃N₄ without NaCl assistance, the 3D OPG-C₃N₄-CN exhibits improved light absorption, reduced carrier recombination and more active sites. As a result, the enhanced hydrogen production of 3D OPG-C₃N₄-CN reaches up to 1590 μmol h⁻¹ g⁻¹ when using Pt as a cocatalyst, which is about six times as much as that of the bulk g-C₃N₄.