Facile Electropolymerization of Manganese-2,5-Dimercapto-1,3,4-Thiadiazole-Based Disulfide-Linked Photoactive Thin Film for Pseudocapacitor and Oxygen Reduction

Incorporation of redox-active centers in metal-organic coordination polymers has gained significant interest due to their tunable electronic properties. To this end, we have electropolymerized a thin film of manganese ions coordinated with a dimercapto thiadiazole metallo-organic polymer (poly-MnDMcT) containing Mn^3+/4+ and S^-2/-1 redox couples. The poly-MnDMcT demonstrated a mixed charge storage mechanism with capacitive and diffusion-controlled contributions coexisting. This metallopolymer symmetric cell setup yielded a specific capacitance of 92.8 F g^-1 at 1 A g^-1 and enhanced cycling stability with retention of 78% over 10,000 cycles @ 4 A g^-1. Correspondingly, the symmetric supercapacitor device produced an energy density of 4 Wh kg^-1 at a power density of 6670 W kg^-1 within a 1.4 V vs Ag/AgCl voltage window. The redox reversibility of manganese ions and ligand disulfide-thiolate units contributes toward enhancement of capacitance and a wider potential window among the class of metallopolymers. Furthermore, the poly-MnDMcT exhibits n-type photoelectrode behavior with repeatable and stable photocurrent responses of 8-10 μA cm^-2 in neutral electrolytes, which opens avenues for photoassisted enhanced charging in energy storage. Moreover, poly-MnDMcT shows enhanced ORR catalytic activity in neutral electrolytes with a current density of −800 μA/cm² at oxygen-saturated conditions. Furthermore, this work enables us to understand and distinguish the current contributions to energy storage and conversion mechanisms when metallo-organic polymers have dual redox sites.