英译汉：However, as the current density increases, the bubbles generated during electrolysis have an increasingly negative impact on the efficiency of the electrolysis. The bubble evolution process in PEMWE includes nucleation, growth, and detachment. On the one hand, the evolution of bubbles reduces the gas supersaturation near the catalytic surface to reduce mass transfer losses, while on the other hand, it masks the catalytic surface to cause an increase in activation loss. The evolution process can be affected by modifying the CL. Designing CL towards increasing the number of bubble nucleation sites, decreasing the bubble detachment size, and increasing the bubble detachment frequency will significantly improve the water electrolysis performance. After detachment, a bubble transport process happens in the PEMWE cell. Bubbles travel from CL to PTL and are then carried away by the water flow in the flow field. The transport routes are determined by the porosity, wettability, and structure of each component in PEMWE. Bubble accumulation during the transport process hinders water-gas transport and reduces cell performance. Especially in the case of dynamic loads, bubble accumulation tends to become severe. Providing sufficient, straightforward, and low-resistance bubble transport routes in CL, PTL, and flow field can reduce bubble accumulation and its negative impact on electrolyzer performance. Future PEMWE components design and electrolyzer control strategies should follow these principles towards better bubble evolution and transport behavior to migrate the bubble-induced loss. More effort needs to be devoted to developing PEMWE bubble management techniques and engaging in engineering practice in the future. In addition, the bubble management techniques in PEMWE also provide guidelines and solution for the bubble issues in AEMWE and thus facilitate its better development. In this article, we have presented a comprehensive review of the bubble evolution and transport behaviors in PEMWE cells and their corresponding impacts on cell performance. In response to the issues induced by bubbles, we have reviewed the most recent advances in bubble management strategies for PEMWE, as well as the remaining challenges and perspectives. Despite the progress made, there is still much room for improvement of water electrolyzer performance regards bubble management due to a limited understanding of bubble evolution and transport in PEMWE. Further development of bubble management in PEMWE can be focused on, but not limited to, the following areas: 1) in-situ characterizations of bubble evolution; 2) modeling the complex multi-scale bubble transport process and its impact on electrochemical performance; 3) optimizing CL and CL-PTL interface for more bubble nucleation sites, smaller bubble detachment size, and higher bubble detachment frequency; 4) designing CL, PTL, flow fields towards sufficient, straightforward and low-resistance bubble transport routes across the whole PEMWE cell; 5) improve electrolyzer operation strategy to prevent bubble accumulation during dynamic load.

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