Recent Advances in Prussian Blue Analogs as Capacitive Deionization Electrode Materials: Fundamentals, Structure–Performance Relationships, and Design Strategies

Capacitive deionization (CDI) is an energy‐efficient desalination technology for low salinity water treatment, but its performance is fundamentally governed by the ion storage capacity of electrode materials, configuration, and operation of the CDI cell. Prussian blue analogs (PBAs) have gained increased attention as Faradaic CDI electrodes due to their unique open framework, compositional tunability, and reversible ion‐insertion behavior. This review critically examines recent advances in PBA‐based CDI electrodes, with emphasis on the interplay between crystal chemistry, electronic structure, and desalination performance. The fundamentals, CDI cell configurations, and key performance metrics are discussed to form the basis of benchmarking performance comparison. Strategies for PBAs performance improvement, including morphology regulation, defect and vacancy engineering, interface and composite design, and electronic structure modulation, are discussed in relation to ion transport, redox activity, and structural stability. Current challenges with respect to scalability, long‐term operation under realistic conditions, need for device‐level consideration, including mass loading, additive, and binder optimization, are discussed as critical for practical desalination consideration. This review provides a comprehensive framework for advancing PBA‐based electrodes toward practical and efficient CDI applications.