This study introduces a doughnut-like, highly porous g-C3N4 photocatalyst fabricated using a double bubble templating method which employs two synergistic gas-generating agents (H2O2 and NH4Cl). The concurrent thermolysis of H2O2 and NH4Cl synergistically enhances g-C3N4 exfoliation and nanopore production, as the released O-2 and NH3 undergo violent exothermic reactions during g-C3N4 growth. The resultant g-C3N4 (H2O2-NH4Cl-g-C3N4) exhibited 8.9 times higher specific surface area compared to bulk g-C3N4, and 3.2-6.4 times as large as those synthesized using individual NH4Cl or H2O2. The photocatalytic activities of these g-C3N4 samples were found to linearly correlate with their valance band( VB) maximum potentials; for example, H2O2-NH4Cl-g-C3N4 possessed a VB maximum down-shifted by 0.34 eV, and consequently exhibited 7.1 times larger photocatalytic hydroquinone degradation rate than the bulk g-C3N4. Electrochemical analysis and trapping experiments collectively suggested that the VB downshift caused more efficient separation of charge carriers, and subsequent enhancement in positive hole-dominated photocatalytic oxidation of hydroquinone. (c) 2017 Elsevier B.V. All rights reserved.