Three-Dimensional Porous Supramolecular Architecture from Ultrathin g-C3N4 Nanosheets and Reduced Graphene Oxide: Solution Self-Assembly Construction and Application as a Highly Efficient Metal-Free Electrocatalyst for Oxygen Reduction Reaction

Direct mixing of aqueous dispersions of ultrathin g-C3N4 nanosheets and graphene oxide (GO) under ultrasonication leads to three-dimensional (3D) porous supramolecular architecture. Photoreduction of GO yields conductive porous g-C3N4/rGO hybrid. The resulting 3D architecture possesses high surface area, multilevel porous structure, good electrical conductivity, efficient electron transport network, and fast charge transfer kinetics at g-C3N4/rGO interfaces, which facilitate the diffusion of O2, electrolyte, and electrons in the porous frameworks during oxygen reduction reaction (ORR). Ultrathin g-C3N4 nanosheet also causes effective electron tunneling through g-C3N4 barrier, leading to rich electrode–electrolyte–gas three-phase boundaries, and shortens the electron diffusion distance from rGO to O2. As a novel ORR catalyst, such 3D hybrid exhibits remarkable catalytic performance, outperformed other g-C3N4/rGO composites, and exhibits excellent durability.