First-principle computational insights on Furan- and Thiophene- functionalized zinc-porphyrins as high performance organic cathodes for electrochemical energy storage systems

• Zn-Porph cathodes demonstrate conductivity, stability, and versatility in EESS. • Thiophene substitution in Zn-Porph stabilizes its redox potential compared to furan. • Thiophene enhances electron affinity, accelerating electron acceptance in Zn-Porph. • Zn-T18 exhibits non-zero DOS at Fermi energy, indicating conductivity. • Complexation with PF6¯ stabilizes zn-Porph across various oxidation states. Organic electrode materials (OEMs) are increasingly replacing conventional inorganic counterparts in metal ion batteries (MIBs) due to their cost-effectiveness and environmental compatibility. Porphyrin-based materials, particularly metalloporphyrins (M-Porph), have garnered significant attention for electrochemical energy storage systems (EESS) owing to their bipolar electrochemical reactivity, making them suitable as both cathodic and anodic materials. However, the correlation between their structure and performance needs further exploration. This computational study examines the redox properties, thermodynamics, and theoretical performance of Zinc(II)-Porphyrin (Zn-Porph) with furan and thiophene substituents. The redox potential (E°) of Zn-Porph changes by 0.17 V with thiophene substituents instead of furan. Thiophene stabilizes the LUMO by 0.105 eV, indicating enhanced electron affinity and faster electron-accepting processes, while the HOMO shows a 0.085 eV stabilization. Thermodynamic calculations reveal that the reduction process intermediates for Zinc(II)-thiophene-Porph are less stable (ΔΔG° = 0.12 eV) than those for furan, suggesting a more accelerated electrochemical process. Additionally, density of states (DOS) analysis of Zn-T18 shows a non-zero DOS at the Fermi energy, indicating available electronic states for occupancy and highlighting its conductive properties. Upon complexation with PF6¯, the Fermi level shifts, reflecting electronic state redistribution and stabilization. The oxidized form, Zn-T16, retains a non-zero DOS at the Fermi energy despite significant Fermi level shifts, ensuring continued electronic conductivity. These findings underscore the robustness and versatility of Zn-porphyrin cathodes in EESS, demonstrating their potential to meet the demands for efficient, cost-effective, and environmentally friendly energy storage solutions.