Synchronous strategy of nanocrystallization and surface modification for g-C3N4 was developed via a facile hydrothermal route in ammonium hydroxide solution. The characterization results reveal that the tailored sample possesses not only an irregular porous structure, higher BET specific surface area, larger band gap, but also rich surface H-bond network. The photocurrent responses and electrochemical impedance spectroscopy indicate that the modification process by ammonium hydroxide via hydrothermal reaction can also accelerate the interfacial charge transfer and improve the separation efficiency of photogenerated charges. As a result, the photocatalytic hydrogen generation rate of tailored g-C3N4 is 4.2 times that of bulk g-C3N4. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.