Hydrogen bubble evolution and its induced mass transfer on zinc electrodes in alkaline and neutral media

The evolution of hydrogen bubbles plays a critical role in governing the performance of Zn-based batteries by influencing Zn deposition, electrode morphology, and mass transfer dynamics. This work consolidates recent progress in understanding the dual influence of hydrogen bubble evolution on Zn-based batteries, emphasizing its implications for mass transfer and electrochemical performance. While presenting challenges such as inhomogeneous Zn deposition, dendrite formation, and Zn passivation, hydrogen bubble evolution simultaneously facilitates mass transfer through its forced convective disturbance. Advanced experimental techniques, including electrochemical mass spectrometry, X-ray microscopy, and gas chromatography, are employed to investigate the complex interplay between the hydrogen evolution reaction (HER) and Zn deposition. The hydrogen bubbles induced by the HER not only promote local convection to enhance the transport of zincate or Zn ions but also serve as templates for forming porous Zn structures to increase the electrochemically active surface area and accelerate reaction kinetics. Finally, emerging strategies are explored to mitigate the detrimental effects of the HER, while capitalizing on its beneficial properties to optimize Zn electrode performance, with the ultimate goal of improving the efficiency, safety, and longevity of rechargeable Zn-based energy storage devices.