Hypothesis: The C3N4 as a cheap and clean photocatalyst shows suitable band gap to splitting water and spectral response. However the poor conductivity of C3N4 limits the photocatalytic hydrogen evolution rate. The combination of C3N4 and high conductivity materials will enhance the separation of photo generated carriers and thus enhance the photocatalytic activity. As many carbon materials have been tried, the mesoporous carbon should be a good candidate to solve this problem. Experiments: A photocatalytic system with C3N4 and mesoporous carbon has been designed to test the photocatalytic performance of both the photocatalytic hydrogen evolution and the photocatalytic degradation of methylene blue. The results of EPR, EIS and PL spectra were given to further understand the photo-generated carrier and its transfer. Findings: The enhancement of the highest hydrogen evolution rate is 48% from 69 to 102 mu mol/h by mesoporous carbon/C3N4 sample. The existence of small amount of mesoporous carbon can facilitate the photogenerated carrier separation, thus enhancing the photocatalytic performance. In the meantime, the introduction of mesoporous carbon into C3N4 is beneficial for improving electron delocalization and conduction electrons and increasing the optical absorption. (C) 2017 Elsevier Inc. All rights reserved.