Onion-liked carbon-embedded graphitic carbon nitride for enhanced photocatalytic hydrogen evolution and dye degradation

Limited light absorption and low charge separation rate are the main obstacles for graphitic carbon nitride (g-C3N4)-based photocatalyst. Here, onion-liked carbon (OLC), a carbon nanostructure with multilayer graphitic shells, was embedded into the g-C3N4 matrix to enhance the photocatalytic performance. Due to its high degree of sp2 hybridization and good electrical conductivity, the OLC can broaden visible light adsorption, narrow the band gap of g-C3N4, and serve as electron acceptor to promote the separation of photo-generated carrier. Thus, the g-C3N4/OLC composites show an increased hydrogen evolution rate of 3086 μmol g−1 h−1, 4.44 times higher than pure g-C3N4. Furthermore, the H2 evolution rate is highly related to the sp2/sp3 ratio of OLC. In addition, efficient photocatalytic degradation of RhB was also achieved (0.1171 min−1). The photocatalytic mechanism was then elucidated through a series of spectrochemical and photochemical test. This work demonstrates the significant applicability of OLC in designing carbon-based photocatalyst with highly-efficient photocatalytic activity towards future solar energy conversion and pollutants degeneration.