A redox flow battery system is provided. The system includes a positive electrode in fluid communication with a positive electrolyte comprising a first metal ion and a negative electrode in fluid communication with a negative electrolyte comprising a second metal ion. An electrically insulating ion conducting surface is provided separating the positive electrode from the negative electrode. Further, the system includes a catalyst surface in fluid communication with the first metal ion, the second metal ion, or a combination thereof, and hydrogen gas, wherein the hydrogen gas and the first metal ion, the second metal ion, or a combination thereof are fluidly contacted at the catalyst surface.