DESC0023936

The intermittent nature of renewable energy resources has increased the demand for auxiliary energy storage and conversion systems like unitized reversible fuel cells. However, these systems usually have low round-trip efficiency, and this shortcoming remains a critical challenge to be solved. To improve unitized reversible fuel cell performance, the porous transport layers are critically important because they are required to effectively perform contradictory roles in the electrolysis cell and fuel cell modes. In the fuel cell mode, a hydrophobic layer is preferred for effective gas transport and water drainage, whereas in the electrolysis cell mode, a hydrophilic layer is more suitable for the facile transportation of water to the catalyst layer for electrochemical water splitting. In this project, we propose to develop a high round-trip efficiency unitized reversible fuel cell integrating the amphiphilic titanium porous transport layers, nanostructured thin film powder catalyst and corresponding catalyst coated membranes. The amphiphilic titanium porous transport layers contain both hydrophobic domains for gas transport in fuel cell mode and hydrophilic domains for water transport in electrolysis cell mode. We will develop strategies to significantly simplify the fabrication process of amphiphilic porous transport layers. Modeling of reversible fuel cells and machine learning will be conducted for the design/optimization of the proposed porous transport layers. In the Phase I project, the titanium amphiphilic porous transport layers will be optimized in terms of the hydrophobic/hydrophilic ratio, thickness, porosity, and pore size distribution. A Multiphysics simulation model will be constructed to understand the relationship between the amphiphilic porous transport layer structure and the unitized reversible fuel cell performance. Then, the titanium amphiphilic porous transport layers and catalyst coated membranes based on nanostructured thin film powder catalyst will be integrated into a 5 cm2 unitized reversible fuel cell to test the round-trip efficiency and evaluate the long-term stability. A round-trip efficiency of 52% will be demonstrated at the end of the Phase I project. The usage of fossil fuels and excessive greenhouse gas emissions would be significantly reduced if usable energy was readily available from clean sources like solar and wind. The proposed project will develop and deliver a low-cost, high-efficiency, and long-durability unitized reversible fuel cell at an appreciable current density. It can be used to store renewable energy as hydrogen and reversely convert the chemical energy in hydrogen back into electricity. In addition, the developed unitized reversible fuel cell technology can be used for power plants to store off-peak electricity, thus reducing plant component stress and promoting efficient plant operations.