ABSTRACT
Alkaline water electrolysis (AWE), a promising technology for the production of green hydrogen, has great potential in the large-scale application of sustainable energy that is motivated by renewable energy sources (e.g., solar, tide, and wind). AWE generally works at relatively low current densities (~0.5 A/cm2) to proceed efficiently, and there is an issue that bubbles could be largely produced on the reactive electrode surface at high current densities, which will have a significant effect on the mass transfer during the water electrolysis process. However, there still lacks clear comprehension in terms of the relation between the behaviors of bubble during evolution and the electrochemical process. This chapter mainly focuses on the effect of bubbles on electrochemical systems and the strategies to promote bubble removal. Firstly, the basic knowledge of the bubble evolution including nucleation, growth, and detachment is presented as it is in connection with AWE electrochemical processes. Then, we provide a detailed summary of the bubbles’ effect on the energy efficiency of AWE from the following perspectives: activation overpotentials, ohmic overpotentials, concentration overpotentials, overpotential fluctuations, mechanical damage, and thermal losses. Finally, we outlined various approaches to mitigate bubble effects, aiming to provide a valuable guide for the design of high-performance electrode material for AWE application.
