Guanidine carbonate assisted supramolecular self-assembly for synthesizing porous g-C3N4 for enhanced photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) is taken as one of the most promising polymer semiconductor photocatalysts for energy conversion. However, the photocatalytic activity of g-C3N4 is usually impeded by the low light absorption and fast recombination of photogenerated carriers. Herein, three-dimensional porous g-C3N4 with controllable morphology are synthesized by thermal polycondensation of supramolecular preorganization assembly of melamine, cyanuric acid and guanidine carbonate (1:1:x, x means the ratio of guanidine carbonate). By adjusting the amount of guanidine carbonate in the assembly, the precursors’ morphology can be changed from microrods to polyhedrons, which affects the g-C3N4 structure accordingly. The optimized hollow porous polyhedral g-C3N4 shows the enhanced light absorption and improved photogenerated carriers separation efficiency, thus exhibiting a 7.7-fold hydrogen evolution activity and 9-fold apparent quantum efficiency (AQE) higher than microtube without addition of guanidine carbonate. This work paves a complementary way towards synthesizing highly efficient photocatalysts through the guanidine carbonate-assisted supramolecular assembly.