17084-13-8 | Potassium hexafluorophosphate

CAS:17084-13-8 | Potassium hexafluorophosphate,Description

Potassium hexafluorophosphate (KPF6) is a salt where the potassium ion (K+) is paired with the hexafluorophosphate anion (PF6-). This compound is of interest due to its stability and its role in various chemical and physical processes. The stability of hexafluorophosphate solutions has been shown to depend on the nature of the counter ion, with potassium providing greater stability compared to sodium and lithium.

Synthesis Analysis

The synthesis of potassium hexafluorophosphate-related compounds often involves the interaction of potassium ions with various fluorine-containing reagents. For instance, potassium tetrahydrogen pentafluoride (K[H4F5]) is prepared by adding anhydrous hydrofluoric acid to potassium fluoride, as demonstrated by its X-ray structure determination. Additionally, complex compounds involving potassium hexafluorophosphate can be synthesized, such as the potassium cobalt monohydrogenophosphate K2Co(H2O)6 2, which is characterized by single crystal X-ray diffraction and other techniques.

Molecular Structure Analysis

The molecular structure of potassium hexafluorophosphate and its complexes has been extensively studied using X-ray crystallography. For example, the structure of potassium tetrahydrogen pentafluoride features a scheelite type structure with potassium and central fluorine atoms at positions of symmetry. In the case of crown ether complexes with potassium hexafluorophosphate, the potassium atoms are linked to the oxygen atoms of the macrocycle and to fluorine atoms of PF6- anions. The structure of potassium difluorophosphate has also been determined, revealing a barium sulphate-like structure with the K+ ion having fourteen oxygen and fluorine neighbors.

Chemical Reactions Analysis

The hydrolysis of potassium hexafluorophosphate in aqueous solutions has been investigated, revealing the formation of various decomposition products such as fluoride, monofluorophosphate, phosphate, and difluorophosphate. These products were identified using ion chromatography and electrospray ionization mass spectrometry. The study of the rotational dynamics of the PF6- anion in various states, including the crystalline and liquid states of ionic liquids, provides insights into the chemical behavior of hexafluorophosphate anions.

Physical and Chemical Properties Analysis

The physical and chemical properties of potassium hexafluorophosphate are closely related to its molecular structure and the interactions within its complexes. The rotational dynamics of the PF6- anion have been characterized by NMR spectroscopy, revealing isotropic rotation with a time scale ranging from picoseconds to hundreds of picoseconds over a temperature range of 180-280 K. The crystal structures of its complexes, such as those with crown ethers, show how the potassium ion interacts with the ligands and anions, affecting the overall properties of the compound. The thermal, magnetic, and dielectric properties of related compounds, such as potassium cobalt monohydrogenophosphate, have also been studied, providing a comprehensive understanding of the behavior of these materials under various conditions.

Scientific Research Applications

1. Conversion Coatings on Magnesium Alloy

• Application Summary: KPF6 is used in the Plasma Electrolytic Oxidation (PEO) process to produce conversion coatings on the AM50 magnesium alloy.
• Methods of Application: The PEO process is carried out in an alkaline-silicate electrolyte with the addition of KPF6, using a unipolar pulse power source. The coating microstructure and its composition are determined using scanning electron microscopy (SEM) and an X-ray photoelectron spectroscopy (XPS).
• Results: The properties of the obtained layer and their anticorrosive resistance strongly depend on the electrolyte composition. The best anticorrosive properties were observed in the layers obtained in the presence of 2.5 g/L KPF6.

2. Anode-Free Lithium Metal Battery

• Application Summary: KPF6 can be used as an electrolyte additive to improve the electrochemical performance of an anode-free lithium metal battery.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

3. Lithium-Sulfur (Li–S) Batteries

• Application Summary: KPF6 can be used to improve the cycling stability and Li Coulombic efficiency of lithium-sulfur (Li–S) batteries.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

4. Perovskite Solar Cells

• Application Summary: KPF6 can be used as an interface modification material to passivate interface defects in perovskite solar cells.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

5. Preparation of Organic Hexafluorophosphate Compounds

• Application Summary: KPF6 is used to prepare 1-butyl-3-methylimidazolium hexafluorophosphate and other organic hexafluorophosphate compounds such as alkylaryliodonium hexafluorophosphates and triarylsulfonium hexafluorophosphates.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

6. Full-Printed Mesoscopic Perovskite Solar Cells

• Application Summary: KPF6 is used as an additive in full-printed mesoscopic perovskite solar cells (MPSCs) to improve their performance and stability.
• Methods of Application: An efficient passivation strategy with KPF6 is proposed to overcome defect and filling issues in MPSCs. The properties of the films and the corresponding performances of MPSCs with KPF6 are systematically investigated.
• Results: The introduction of KPF6 improves the crystallinity, defect issues, filling of the perovskite in the mesoporous structure, and hydrophobicity of the MPSCs. This results in the inhabitation of non-radiative recombination loss, and raises the photoelectric performance and stability. The power conversion efficiency (PCE) of the champion devices reached 15.39%, which is significantly raised by ∼10% against that of the control devices (14.16%). The unencapsulated MPSCs with KPF6 maintain 95% of their initial PCE after 50 days stored in air (25 ± 5 °C @ 50 ± 5% RH), while the MPSCs without KPF6 only maintain 80% of their initial PCE.

7. Cationic Polymerization Reactions

• Application Summary: KPF6 is used in cationic polymerization reactions as photo initiators.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

8. Preparation of Alkylaryliodonium Hexafluorophosphates

• Application Summary: KPF6 is used to prepare alkylaryliodonium hexafluorophosphates.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

9. Preparation of Triarylsulfonium Hexafluorophosphates

• Application Summary: KPF6 is used to prepare triarylsulfonium hexafluorophosphates.
• Methods of Application: The specific methods of application are not detailed in the source.
• Results: The specific results or outcomes are not detailed in the source.

Safety And Hazards

Potassium hexafluorophosphate is considered hazardous. It causes severe skin burns and eye damage. It is harmful if swallowed, in contact with skin, or if inhaled. It should not be released into the environment.

Future Directions

Potassium hexafluorophosphate can be used as an electrolyte additive to improve the cycling stability of lithium–sulfur (Li–S) batteries. It can also be used as interface modification material to passivate interface defects in perovskite solar cells.

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