Core-Shell Redox-Nanoparticles Integrate High Ammonium Selectivity with Long-Term Stability

Area of Science:

• Materials Science
• Electrochemistry
• Environmental Science

Background:

• Copper-based Prussian blue analogues (PBAs) show promise for selective ammonium intercalation.
• Limited cycling stability of PBAs hinders practical applications in ammonium removal.
• Developing stable and selective materials is crucial for resource recovery.

Purpose of the Study:

• To design core-shell heterostructured PBAs for enhanced ammonium selectivity and cycling stability.
• To investigate the effect of nickel hexacyanoferrate shell thickness on performance.
• To demonstrate efficient ammonium extraction from wastewater.

Main Methods:

• Synthesis of core-shell copper hexacyanoferrate@nickel hexacyanoferrate (CuHCF@NiHCF) nanoparticles via two-step coprecipitation.
• Precise control of NiHCF shell thickness (10 nm and 20 nm).
• Electrochemical characterization, including charge-discharge cycling and electrosorption experiments in a flow cell.

Main Results:

• Core-shell CuHCF@NiHCF nanoparticles maintained over 98% capacity after 1000 cycles.
• 10 nm shell particles showed high NH₄⁺/Na⁺ selectivity (9.2) and uptake (0.42 mmol g^-1).
• Selectivity exceeded 20 with voltage control, and efficient NH₄⁺ extraction from wastewater was demonstrated.

Conclusions:

• Shell thickness control is a viable strategy to enhance both ammonium selectivity and electrochemical stability.
• CuHCF@NiHCF core-shell structures offer a promising platform for sustainable ammonium recovery.
• This approach facilitates efficient ammonium extraction from complex matrices like municipal wastewater.