In this work, the chlorine-doped and undoped hydrothermal carbonation carbon (Cl-HTCC, HTCC) photo catalysts were used to study the correlation of their interfacial charge and photocatalytic performance. For degradation of aromatic dye, rhodamine B (RhB), Cl-HTCC manifests much better photocatalytic performance compared with that of undoped HTCC. Besides the slightly enhanced charge transfer brought, the Cl-HTCC showed more negatively interfacial charge and thus a stronger adsorption of positively charged RhB. This made the photogenerated holes (h(+)) directly react with the adsorbed RhB, which does not require the h(+) to produce hydroxyl radical ((OH)-O-center dot) and reduce its lost during the transformation, thus enhanced the performance of Cl-HTCC. While for undoped HTCC, it showed a weaker adsorption of RhB, and the photogenerated h(+) firstly reacted with H2O molecules to produce (OH)-O-center dot. Then, the (OH)-O-center dot can attack the RhB. Besides, the intermediates and the degradation pathways are also evaluated here via UPLC-MS. Results show that the interfacial charge also dominated the degradation pathways. This work provides a novel metal-free photocatalyst for environmental remediation and will inspire further efforts to enhance the photocatalytic performance by concerning interfacial conditions. (C) 2019 Elsevier Inc. All rights reserved.