Particle size reduction of manganese-doped Prussian blue analogues enhanced hybrid capacitive deionization performance

Abstract

The hybrid capacitive deionization (HCDI) technology has demonstrated improved efficiency compared to conventional capacitive deionization (CDI). Prussian blue analogues (PBAs) possess high capacity and rapid ion transfer capability, recognized as promising materials for HCDI electrodes. PBAs with a more uniform morphology and smaller particle size could enhance contact with the electrolyte, and facilitate rapid ion transport. It has been observed that adding manganese can reduce the particle size of these materials and lead to a more uniform structure. In this study, nickel-based Prussian blue analogues were modified with varying manganese doping ratios to enhance desalination properties. The optimal desalination performance was achieved when the atomic ratio of manganese to nickel was 3:7 (MNP-3), yielding a maximum deionization rate of 20.59 mg·(g·min)⁻¹ and a high desalination capacity of 58.82 mg·g⁻¹ in batch mode testing at an applied voltage of 1.2 V in a 500 mg·L⁻¹ NaCl feed solution. Furthermore, MNP-3 exhibited higher specific capacitance and smaller transfer resistance than the undoped material, which were advantageous for sodium ion storage. This study emphasizes the impact of particle size on HCDI performance, providing valuable insights for future HCDI application studies.