Editing Prussian blue (section)

=== Battery materials ===
[[File:2016-Wu 2.png|thumb|[[cyclic voltammetry|Cyclic voltammograms]] of Prussian Blue [[electrode]] in solution of different [[Alkali metal|alkali]] [[cations]]]]
Prussian blue (PB) has been studied for its applications in electrochemical energy storage since 1978.<ref name="Neff1978">{{Cite journal|last=Neff|first=Vernon D.|date=1978-06-01|title=Electrochemical oxidation and reduction of thin films of Prussian blue|url=https://iopscience.iop.org/article/10.1149/1.2131575/meta|journal=Journal of the Electrochemical Society|language=en|volume=125|issue=6|pages=886–887|doi=10.1149/1.2131575|bibcode=1978JElS..125..886N|issn=1945-7111}}</ref> Prussian blue proper (the Fe-Fe solid) shows two well-defined reversible redox transitions in K<sup>+</sup> solutions. Weakly solvated potassium ions (as well as Rb<sup>+</sup> and Cs<sup>+</sup>, not shown) have the [[solvated radius]], which fits the framework of Prussian Blue. On the other hand, the sizes of solvated Na<sup>+</sup> and Li<sup>+</sup> are too large for the PB cavity, and the intercalation of these ions is hindered and much slower. The low and high voltage sets of peaks in the cyclic voltammetry correspond to 1 and {{sfrac|2|3}} electron per Fe atom, respectively.<ref name="Neff1985">{{cite journal | last=Neff | first=Vernon D. | date=1985-06-01 | title=Some performance characteristics of a Prussian blue battery | journal=Journal of the Electrochemical Society | volume=132 | issue=6 | pages=1382–1384 | issn=0013-4651 | doi=10.1149/1.2114121| bibcode=1985JElS..132.1382N }}</ref> The high voltage set is due to the {{Chem2|Fe(3+)/Fe(2+)}} transition at the low-spin Fe ions coordinated to C-atoms. The low-voltage set is due to high-spin Fe ion coordinated to N-atoms.<ref name="Itaya1986">{{cite journal | last1=Itaya | first1=Kingo | last2=Uchida | first2=Isamu | last3=Neff | first3=Vernon D. | date=1986-06-01 | title=Electrochemistry of polynuclear transition metal cyanides: Prussian blue and its analogues | journal=Accounts of Chemical Research | volume=19 | issue=6 | issn=0001-4842 | doi=10.1021/ar00126a001 | pages=162–168}}</ref><ref name="Wu2016">{{cite journal | last1=Wu | first1=Xianyong | last2=Shao | first2=Miaomiao | last3=Wu | first3=Chenghao | last4=Qian | first4=Jiangfeng | last5=Cao | first5=Yuliang | last6=Ai | first6=Xinping | last7=Yang | first7=Hanxi | date=2016-09-14 | title=Low defect FeFe(CN)<sub>6</sub> framework as stable host material for high performance Li-ion batteries | journal=ACS Applied Materials and Interfaces | volume=8 | issue=36 | pages=23706–23712 | issn=1944-8244 | doi=10.1021/acsami.6b06880| pmid=27556906 }}</ref><ref name="Fayaz2024">{{cite journal | last1=Fayaz | first1=Muhammad | last2=Lai | first2=Wende | last3=Li | first3=Jie | last4=Chen | first4=Wen | last5=Luo | first5=Xianyou | last6=Wang | first6=Zhen | last7=Chen | first7=Yingyu | last8=Li | first8=De | last9=Abbas | first9=Syed Mustansar | last10=Chen | first10=Yong | year=2024 | title=Prussian blue analogues and their derived materials for electrochemical energy storage: Promises and challenges | journal=Materials Research Bulletin | publisher=Elsevier | volume=170 | page=112593 | issn=0025-5408 | doi=10.1016/j.materresbull.2023.112593}}</ref>

It is possible to replace the Fe metal centers in PB with other metal ions such as Mn, Co, Ni, Zn, to form electrochemically active Prussian blue analogues (PBAs). PB/PBAs and their derivatives have also been evaluated as electrode materials for reversible alkali-ion insertion and extraction in [[lithium-ion battery]], [[sodium-ion battery]], and [[potassium-ion battery]].{{cn|date=January 2025}}