Zn/Mg Metal-Organic Framework Composite for Energy Storage via Cobalt Phthalocyanine Dye in a Self-powered Photosupercapacitor

Abstract

This work presents a photosupercapacitor (PSC) integrating a co-sensitized TiO₂/CdS/CoPc photoanode for efficient solar energy harvesting with a high-performance Zn/Mg metal-organic framework (MOF-5/NICS-6) composite cathode for charge storage. The PSC exhibits fast photo-charging to ∼0.7 V within seconds under illumination and delivers a high discharge specific capacity (SC) of ∼235 C g⁻¹ at 1 A g⁻¹ in the dark. The MOF-5/NICS-6 composite, when evaluated independently as an asymmetric supercapacitor (ASC) cathode, achieves a remarkable SC of 258.3 C g⁻¹ at 1 A g⁻¹, energy and power densities up to 25 Wh kg⁻¹ and 4.5 kW kg⁻¹, and excellent cycling stability over 6000 cycles with 80% retention. The inadequate light-harvesting capabilities of conventional photoanodes and poorly electrocatalytic counter electrodes limit the production and separation of photogenerated holes and electrons. Use of a photoanode co-sensitized with CoPc and CdS enables broad spectral utilization and reduces recombination losses. Simultaneously, the MOF composite cathode allows efficient reduction of sulfide species maximizing charge separation in the solar part and stores charge efficiently in the supercapacitor part resulting in an overall photo-conversion and storage efficiency of 11.4%. The PSC retains 68% of its initial capacity after 100 photo-charging/discharging cycles, highlighting the robustness and stability of the rationally designed cell.