ElectroChem proposes technology advances in its unique PEM IFF water electrolyzer design to meet the NASA requirement for an electrolyzer that will operate very efficiently both at low current densities and at high pressures. This SBIR effort will develop technical solutions to the draw-back of high pressure operation, namely hydrogen gas crossover losses, that is, an increased diffusion of hydrogen across the membrane which effectively decreases the efficiency. Two approaches to reducing gas permeation through the membrane at high pressure will be investigated: 1) The use of palladium thin films embedded in the membrane; and 2) The use of Nafion proton conductive polymer-clay nanocomposite blends. Two different bonding approaches and membrane configurations will be used for the first approach. Determining the best composition is the key for the second approach. Promising candidates will be determined by two tests: 1) hydrogen permeability tests; and 2) proton conduction measurements to assure that the effects of reducing hydrogen permeability will not affect electrochemical proton conduction. Finally, the most promising candidates will undergo their final Ph I proof of concept tests in a PEM IFF electrochemical cell. Phase I will lead to the Ph II development of a complete PEM IFF Electrolyzer System and delivery of a demonstration unit to NASA.