Hi Manish Kumar ,

Based on your research focus on Na-S batteries and polysulfide adsorption tests, here's a comprehensive analysis of Na₂S air stability and practical recommendations:

⚠️ ​​1. Na₂S Air Stability: Critical Concerns​​

​​No​​, Na₂S is ​​not air-stable​​ due to its high reactivity with atmospheric components:

• ​​Hydrolysis with moisture​​: Releases toxic H₂S gas (rotten egg odor) and forms NaOH, increasing solution alkalinity .
• ​​Oxidation by oxygen​​: Forms polysulfides (Na₂Sₓ, where x=2–8) and sulfites, leading to yellow/red discoloration in commercial grades (e.g., 60% Na₂S flakes) .
• ​​Carbonation by CO₂​​: Generates carbonate impurities that may clog adsorbent pores .

⚡️ ​​2. Implications for Na-S Battery Research​​

For polysulfide adsorption tests, unstable Na₂S causes:

• ​​Inaccurate adsorption metrics​​: Oxidized products (e.g., Na₂S₂O₃, Na₂SO₃) compete with Na₂Sₓ (4≤x≤8) for adsorption sites, skewing capacity measurements .
• ​​Solution pH shifts​​: NaOH from hydrolysis alters adsorbent surface charge (e.g., biochar), reducing polysulfide affinity .
• ​​Electrode contamination​​: Sulfide decomposition products (e.g., Na₂CO₃) deposit on adsorbents, degrading cycling stability .

🧪 ​​3. Handling & Storage Recommendations​​

To mitigate degradation during polysulfide adsorption tests:

• ​​Storage​​: Keep in sealed containers under inert atmosphere (Ar, N₂), with H₂O/O₂ levels 495 mg/g Pb²⁺ adsorption .

For extended stability, consider ​​carbon-coated Na₂S​​ (e.g., pyrolyzed PVP shells), which suppresses H₂S release and oxidation by >90% . This approach is ideal for long-term Na-S battery studies.

If you would like to learn more interesting information about Na₂S, you can refer to this article we published："Na2S in-situ infiltrated in actived carbon as high-efficiency presodiation additives for sodium ion hybrid capacitors."

Anyhow, good luck with Na2S!

Cheers

Mengfan Pei

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@mengfan pei thank you very much and surely I will read your article.