Improved Membranes for Solar Fuels Generators

Solar fuels generators harness solar energy as the power source to generate either hydrogen or carbon-based fuels. In both cases, water is electrochemically oxidized to produce oxygen, protons, and electrons at the anode. Hydrogen or carbon-based fuels are produced at the cathode by the reduction of protons or carbon dioxide, respectively. Cation exchange membranes are a critical, cost determining, component of the system, but current commercially available membranes are not able to meet the challenging requirements of this developing technology. This work will focus on the development of new cation exchange membranes that address the challenges of both solar-to-hydrogen and solar-to-carbon fuels generators. Novel membranes will be developed which demonstrate reduced hydrogen permeation (to improve efficiency and limit hazardous mixing of hydrogen and oxygen), reduced costs and improved durability compared with existing materials. Additional requirements for solar-to-carbon fuels membranes such as chemical stability and low permeability to potential products will also be addressed. We have successfully demonstrated the development and fabrication of novel membranes which significantly outperform current commercial materials in key properties critical for effective solar fuels generation. This was achieved through systematic modification of the molecular architecture and chemical functionality of ion exchange membranes developed in our laboratories. Key achievements include efficient cation conductivity in conjunction with greatly reduced hydrogen crossover and carbon-based fuel (methanol) permeability, which will allow the use of thinner membranes and significant cost savings over the large surface areas required for effective solar energy capture and fuel generation. We intend to further customize our best performing membranes to meet the highly specific requirements of both solar-to-hydrogen and solar-to-carbon fuels generators with a focus on enhancing long term durability, optimizing efficiency and device component integration and minimizing costs. Prototype devices will be further developed and scaled up in order to demonstrate the potential for commercially viable solar fuels production. Success of this work would be an important step towards realizing cost effective renewable fuel production and realizing the Hydrogen Shot 1-1-1 target of $1 / Kg for green hydrogen by 2030. Critical areas which would benefit include industrial gas applications/chemical feedstocks, transportation fuels and power backup/storage. For each of these applications, the use of solar generated fuels would result in a reduced dependence on fossil fuels and the associated economic, political, and environmental issues related to their extraction, refinement, supply and final use.