In this study, an effective catalyst reuse strategy for formic acid hydrogen generators was developed. Characterization and performance tests were conducted using Pd/mpg-C3N4 and Pd/NH2-mpg-C3N4 catalysts to investigate the effect of amine functionalization. Amine functionalization positively affected the catalyst characteristics and activity. The reusability of the catalyst was evaluated through repeated hydrogen generator tests. The experimental and analytical results indicated that re-functionalization significantly improved the catalyst reusability compared with washing. Hence, the re-functionalization can effectively improve the practicality of formic acid hydrogen generators.