Abstract: The present invention is directed to a method and system for supplementing fuel for an internal combustion engine by applying a current across a cathode and an anode in an aqueous electrolyte solution to generate fuel gas such as hydrogen; directing the fuel gas to fill a collapsible bag; directing the fuel gas past the collapsible bag to the internal combustion engine when the collapsible bag is full; and allowing the fuel gas that filled the collapsible bag to be drawn into the engine when the engine requires a fuel boost.