Transforming energy storage with unitized regenerative fuel cells: Challenges and future potential

The rapid expansion of renewable energy sources has significantly increased the need for efficient and scalable energy storage solutions. Among the various technologies, unitized regenerative fuel cells (URFCs) have emerged as promising candidates due to their unique ability to transition seamlessly between fuel cell (FC) and water electrolyser (WE) modes. This review explores the advancements in materials, performance, challenges, and applications of the URFC system. It delves into the key components of URFCs, including membranes, catalysts, electrodes, and gas diffusion layers, analysing their roles in optimizing performance during both FC and WE modes. The importance of materials such as proton exchange membrane (PEM), catalyst stability, and electrode design for improving energy efficiency, power density, and round-trip efficiency (RTE) is highlighted. The review also addresses critical challenges including expensive electro-catalysts, catalyst degradation, and corrosion of supporting materials, emphasizing ongoing research efforts to mitigate these issues. Furthermore, the paper discusses the benefits of URFCs over traditional batteries, such as longer energy storage periods and fewer cycle limitations. Applications in grid-scale energy storage, renewable energy integration, and transportation are also examined, showcasing the versatile potential of URFCs across various sectors. Finally, future perspectives on scalability, system integration, and material innovations are presented, highlighting the continued evolution of URFC technology for broader commercial deployment.