The photocatalytic production of H-2 using carbon-doped TiO2 (C-TiO2) nanoparticles has been investigated in single or mixed systems of organic fatty acids (OFAs) under visible light irradiation, including acetic acid, propionate acid, butyric acid and lactic acid. When OFAs were applied at the same electron density (10 e-eq L-1), the H-2 evolution rates followed the order of propionic acid > butyric acid approximate to acetic acid > lactic acid, whereas at the same molar concentration (0.5 mol L-1), that order changed to lactic acid > acetic acid > butyric acid approximate to propionic acid. This result implied that the electron transfer efficiency differed from four OFAs, probably due to their different affinity with C-TiO2. and CH3. partially contributed to OFAs degradation and H-2 production. The quantum dynamics simulations of electron transfer revealed that the dominant mechanism of H-2 production was direct electron transfer from adsorbed OFAs to C-TiO2. This work aims to pursue the synergy of solar energy utilization and conversion of OFAs into H-2. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.