| Summary: | In 2007, the US Department of Energy recommended a no-go on NaBH<sub>4</sub> hydrolysis for onboard applications; however, the concept of a NaBH<sub>4</sub>-H<sub>2</sub>-PEMFC system has the potential to become a primary source for on-demand power supply. Despite the many efforts to study this technology, most of the published papers focus on catalytic performance. Nevertheless, the development of a practical reaction system to close the NaBH<sub>4</sub>-H<sub>2</sub> cycle remains a critical issue. Therefore, this work provides an overview of the research progress on the solutions for the by-product rehydrogenation leading to the regeneration of NaBH<sub>4</sub> with economic potential. It is the first to compare and analyze the main types of processes to regenerate NaBH<sub>4</sub>: thermo-, mechano-, and electrochemical. Moreover, it considers the report by Demirci et al. on the main by-product of sodium borohydride hydrolysis. The published literature already reported efficient NaBH<sub>4</sub> regeneration; however, the processes still need more improvements. Moreover, it is noteworthy that a transition to clean methods, through the years, was observed.
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