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. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

By controlling the ratio of guanidine carbonate in the supramolecular assembly, three-dimensional porous g-C3N4 with controllable morphology were successfully synthesized, showing enhanced light absorption and improved photogenerated carrier separation efficiency. The hydrogen evolution activity and apparent quantum efficiency of the optimized hollow porous polyhedral g-C3N4 were 7.7-fold and 9-fold higher, respectively, compared to microtube materials without guanidine carbonate addition.