Can Intermediate Temperatures be a "Goldilocks Zone" for Green Hydrogen Production?

Green or renewable hydrogen is steadily emerging as an attractive solution in the global energy transition, offering a sustainable pathway to decarbonize hard-to-abate sectors such as steel, ammonia, and methanol, among others. Its production via water electrolysis is dominated by four main technologies: alkaline, proton exchange membrane (PEM), anion exchange membrane (AEM), and solid oxide electrolyzer cells (SOECs), each with distinct advantages and limitations. While electrolyzers operating at temperatures less than 100 °C such as alkaline and PEM are commercially mature, they suffer from lower efficiencies. In contrast, high-temperature systems such as SOECs or emerging protonic ceramic electrochemical cells (PCECs) promise superior performance but introduce complexity and durability challenges. Positioned between these extremes is intermediate-temperature water electrolysis (ITWE), operating between 100 and 400 °C, which may offer an optimal balance of efficiency, material stability, and system simplicity. Despite growing academic interest, ITWE remains largely overlooked and underexplored, particularly from a practical, deployment-oriented standpoint. This perspective presents a holistic reflection on ITWE, critically examining its thermo/electrochemistry, scientific and engineering challenges, techno-commercial promise and trade-offs, and potential deployment scenarios while proposing future directions for research and innovation in the context of large-scale green hydrogen production.