Water Electrolysis toward Elevated Temperature: Advances, Challenges and Frontiers

Since severe global warming and related climate issues have been caused by the extensive utilization of fossil fuels, the vigorous development of renewable resources is needed, and transformation into stable chemical energy is required to overcome the detriment of their fluctuations as energy sources. As an environmentally friendly and efficient energy carrier, hydrogen can be employed in various industries and produced directly by renewable energy (called green hydrogen). Nevertheless, large-scale green hydrogen production by water electrolysis is prohibited by its uncompetitive cost caused by a high specific energy demand and electricity expenses, which can be overcome by enhancing the corresponding thermodynamics and kinetics at elevated working temperatures. In the present review, the effects of temperature variation are primarily introduced from the perspective of electrolysis cells. Following an increasing order of working temperature, multidimensional evaluations considering materials and structures, performance, degradation mechanisms and mitigation strategies as well as electrolysis in stacks and systems are presented based on elevated temperature alkaline electrolysis cells and polymer electrolyte membrane electrolysis cells (ET-AECs and ET-PEMECs), elevated temperature ionic conductors (ET-ICs), protonic ceramic electrolysis cells (PCECs) and solid oxide electrolysis cells (SOECs).

Automated summary

Severe global warming caused by fossil fuel utilization necessitates the development of renewable resources and the conversion of unstable chemical energy to overcome their fluctuation-related challenges. As an environmentally friendly and efficient energy carrier, hydrogen can be produced directly by renewable energy. However, the high cost of large-scale green hydrogen production through water electrolysis impedes its competitiveness, which can be resolved by enhancing thermodynamics and kinetics at elevated working temperatures. This review primarily focuses on the effects of temperature on electrolysis cells, providing multidimensional evaluations on materials and structures, performance, degradation mechanisms and mitigation strategies, and electrolysis in stacks and systems.