Water electrolysis for hydrogen production requires highly active and inexpensive catalysts. Herein, we combine ultrasonic impact nanocrystallization (UIN) technology with nital etching method to rapidly prepare highly efficient self-supporting Cu electrode with abundant low-angle grain boundaries. When used as a catalyst for hydrogen evolution reaction (HER), the as-prepared electrode exhibits an overpotential of 353 mV at a current density of 10 mA cm−2, which is about 200 mV lower than that of the blank Cu plate. Moreover, the overpotential decreased to 246 mV after the stability test of 100 h, indicating a self-optimizing property. This work paves a new way for the preparation of self-supporting electrode with high performance. • Ultrasonic impact nanocrystalline could be used in catalysis. • Cu self-supporting electrode with high density surface dislocation is prepared. • The dislocation density could be precisely adjusted by controlling the etching time. • Electrode exhibits high HER activity and stability, shows self-optimized performance. • Dislocations have lower hydrogen adsorption free energies than perfect crystals. [ABSTRACT FROM AUTHOR]