Synergistic enhancement of capacitance and catalysis by cobalt binary ligand complexes on porous carbon and nano silica

Abstract

Three novel cobalt-based complexes, Co(HBTC)_0.5(4,4′-bipy)Cl (1), Co(HBTC)_0.5(4,4′-bipy)Cl/PC (1/PC), and Co(HBTC)_0.5(4,4′-bipy)Cl/NS (1/NS), were prepared with porous carbon (PC) and nano silica (NS) to enhance catalytic and energy storage durability and reusability. (1)/PC exhibited outstanding catalytic efficiency in methyl orange (MO) reduction, maintaining over 119 cycles with a TON of 38.2 mg MO per mg catalyst. Conversely, (1) showcased superior reduction capacity for methylene blue (MB), sustaining 41 cycles with a TON of 12.96 mg MB per mg catalyst. Structural analysis revealed that (1) exhibits high crystallinity, whereas the incorporation of PC and NS results in diminished diffraction intensities. Raman spectroscopy identified carboxylate bonds, while XPS confirmed the presence of Co(II) oxidation states. Thermal analysis indicated a gradual ligand loss, influencing the robustness of the framework. The (1)/PC electrode exhibited outstanding electrochemical behavior in 2 M KOH, delivering a high specific capacitance of 856.4 F g⁻¹ at 1 A g⁻¹ and retaining 88.84% of its initial capacitance after 3300 cycles. Cyclic voltammetry confirmed faradaic charge-storage contributions, while charge–discharge analysis indicated rapid ion diffusion and better surface area. These features, arising from the synergistic integration of porous carbon with abundant electroactive sites, highlight (1)/PC as a promising candidate for advanced supercapacitor applications. This study establishes (1)/PC as a promising multifunctional material for both environmental remediation and advanced energy storage, paving the way for future applications in sustainable technologies.