This disclosure relates to energy storage and generation systems, e.g., combination of flow battery and hydrogen fuel cell, that exhibit operational stability in harsh environments, e.g., both charging and discharging reactions in a regenerative fuel cell in the presence of a halogen ion or a mixture of halogen ions. This disclosure also relates to energy storage and generation systems that are capable of conducting both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) in the same system. This disclosure further relates to energy storage and generation systems having low cost, fast response time, and acceptable life and performance.