Anion Exchange Membrane for High Efficiency Solar-to-Hydrogen Generation

Hydrogen is an excellent alternative to fossil fuels because it is storable, transportable, and burns cleanly, producing power without polluting the environment. Direct solar-to-hydrogen generation would enable the conversion of renewable energy and water into a storable fuel, thereby drastically reducing carbon emissions. However, solar-driven water splitting devices are hindered by lack of optimized materials, especially membranes, for the unique challenges associated with solar fuel formation. To improve utilization of solar energy and reduce fossil fuel consumption, Giner is proposing a device to convert solar energy and water directly into storable hydrogen fuel. It will integrate novel anion exchange membrane technology originally developed by Dr. Yushan Yan and subsequently commercialized at W7energy, electrocatalysts and photoelectrodes developed by Dr. James McKone, and Giner’s established water electrolysis platform. This solar-powered water-splitting device will directly generate hydrogen and oxygen from water, using only sunlight as an energy source. Anion exchange membranes developed at W7energy were tested for stability under simulated solar light. In inert atmosphere, these membranes demonstrated <1% loss of ion exchange capacity (IEC) and no loss of functional group cations in strong base for over 140h under sunlight. In open air they demonstrated <2% IEC loss and no cation loss for over 70 h, but suffered some mechanical degradation, suggesting some oxidative stress to the membrane backbone under sunlight. These membranes were also used in traditional electrolyzers and displayed stable performance for over 500 h operating at 0.5 A/cm2 in pure water. Hyperbranched polymer membranes were also developed that show promising initial results, forming transparent, flexible membranes that were stable under the simulated solar light in air, with IECs comparable to the W7energy baseline membranes. We plan to develop an anion exchange membrane that is stablefor over1000hundersunlight.We will develop electrocatalysts that show hydrogen production rates exceeding 100 mA/mg at 300 mV total overpotential in alkaline or neutral conditions. These materials will integrate into a direct solar-to-hydrogen conversion device based on Giner’s established 100 cm2 electrolysis platform, which will demonstrate solar-to-hydrogen efficiency exceeding 10%. Hydrogen obtained directly through solar-driven water splitting would provide a storable, scalable fuel source without greenhouse gas emissions with no need for external power sources (other than solar) or electrical conversion systems. The commercial development of a direct solar-to-hydrogen device, as proposed herein, would enable hydrogen production for fuel in remote areas without reliable electricity, transportation infrastructure, or after a natural disaster event, because it requires only sunlight and water to operate.