▎ 摘　　要

Exploring efficient and stable catalysts synthesized by innovative methodologies is extremely important for hydrogen evolution reactions. Herein, we prepared the palladium nanocrystals (Pd NCs) with different morphologies (triangle, nanocubes, and nanodendrites) supported on graphene nanosheets (GNS) by facile hydrothermal method. The shape of Pd-nanodendrites/GNS can be controlled by adjusting hydrothermal reaction time. More importantly, the crystal defects in the Pd-nanodendrites/GNS, such as steps, terraces, and edge-sites atoms, will effectively serve as catalytic active sites. Compared with other morphologies, the Pd-nanodendrites/GNS exhibited superior HER activity in the 1 M KOH solution, such as small overpotential (39.6 mV) required to achieve a 10 mA cm(-2) current density, ultra-low Tafel slope (29.7 mV dec(-1)), and lower charge transfer resistance (R-ct) value of 16.2 Omega, which indicates good conductivity and high electrochemical stability. This work offers a new opportunity to design advanced electrocatalysts for highly efficient HER in alkaline media.