© 2020 Elsevier B.V. Two dimensional (2D) hexagonal-shape gallium nitride (HS-GaN) was synthesized by reacting GaCl3 and LiNH2 with LiCl as the molten salt. We demonstrated that the size and shape of 2D plate-like GaN nanoplates could be controlled under a relatively low temperature from 600 °C to 700 °C. TEM analysis revealed that the single crystal of HS-GaN has a plate-like morphology with diameter and thickness of 450 nm and 80 nm, respectively. The photo-electrochemical cell fabricated using the HS-GaN electrode showed a higher current by a factor of up to 2 compared to that using random-shaped GaN particles under UV light irradiation. The precise growth control of 2D GaN crystals will facilitate new methods of developing high-performance photo-energy conversion materials.