This disclosure relates to electrochemical systems, e.g., a combination of an electrical energy source and an electrical energy storage system having a regenerative fuel cell system, that exhibit operational stability in harsh environments, e.g., both charging and discharging reactions in a regenerative fuel cell in the presence of an acid or a mixture of acids, or a halogen ion or a mixture of halogen ions. The electrochemical systems are capable of conducting both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) in the same system. The electrochemical systems have low cost, fast response time, and acceptable life and performance. This disclosure also relates to methods of operating the electrochemical systems containing a regenerative fuel cell system.