Optimizing s-p Orbital Overlap Between Sodium Polysulfides and Single-Atom Indium Catalyst for Efficient Sulfur Redox...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• P-block metal carbon-supported single-atom catalysts (C-SACs) show promise for room-temperature sodium-sulfur (RT Na-S) batteries.
• Understanding the electronic interactions between sodium polysulfides (NaPSs) and p-block C-SACs is crucial for optimizing battery performance.
• Current understanding of electronic-level interactions limits precise control over catalyst design and electro-catalytic activity.

Purpose of the Study:

• To propose and validate the s-p orbital overlap degree (OOD) as a descriptor for evaluating p-block C-SACs in RT Na-S batteries.
• To investigate the relationship between s-p OOD and the catalytic activity for sulfur reduction (SRR) and sulfur oxidation (SOR) reactions.
• To demonstrate the effectiveness of catalysts designed using the OOD descriptor in achieving high-performance RT Na-S batteries.

Main Methods:

• Theoretical calculation of s-p orbital overlap degree (OOD) between Na in NaPSs and p-orbitals of p-block C-SACs.
• Comparison of OOD, shuttle effect, and reaction energy barriers for different C-SACs, including nitrogen-doped graphene (NG) and NG-supported InN4 (NG-InN4) and InN5 (NG-InN5) SACs.
• Electrochemical testing of RT Na-S pouch batteries utilizing the designed NG-InN5 SACs.

Main Results:

• The nitrogen-doped graphene-supported InN5 (NG-InN5) SACs exhibited the largest s-p OOD.
• NG-InN5 SACs demonstrated the weakest shuttle effect and the lowest energy barriers for both SRR and SOR compared to other catalysts.
• Na-S pouch batteries with NG-InN5 catalysts achieved a high capacity of 490.7 mAh g⁻¹ at 2 A g⁻¹ with 96% Coulombic efficiency at a low electrolyte/sulfur ratio of 4.5 μl mg⁻¹.

Conclusions:

• The s-p orbital overlap degree (OOD) serves as an effective descriptor for the interaction between NaPSs and p-orbital-dominated catalysts in RT Na-S batteries.
• The proposed descriptor facilitates the rational design of advanced C-SACs for high-performance sodium-sulfur batteries.
• This work provides a new avenue for precisely controlling catalyst coordination environments and electro-catalytic activity for next-generation energy storage.