A system for humidifying a fuel cell includes: a container including an aqueous solution of hydrogen peroxide; a source of pressurized gas coupled to the container for pressurizing the hydrogen peroxide solution container; and a catalyst reaction chamber including a catalyst for decomposing hydrogen peroxide into a gaseous mixture of water vapor and oxygen. The gaseous mixture of water vapor and oxygen is combined with a flow of reactant oxidant gas to obtain a humidified oxidant gas stream, which is delivered to the fuel cell.