In Situ Polymerized Polyaniline in Redox-Active Metal-Organic Polyhedra for Supercapacitors

The introduction of porosity into polyaniline (PANI) is key for enhancing its capacitive performance because both electrons and counterions need to migrate through the whole material during the charge-discharge process. Here, we demonstrated the incorporation of redox-active metal-organic polyhedra (MOPs) as intrinsic porous materials into PANI. Two redox-active and structurally stable ruthenium-based MOPs, SO₃-RuMOP and t-Bu-RuMOP, were employed as additives during the solution-phase oxidative polymerization of aniline. This approach produced two series of nanocomposites with various ratios between MOPs and PANI. Dynamic light scattering measurements were used to trace the hydrodynamic diameters of solid products formed during the polymerization process and to investigate the effect of different MOPs on the process. Electron microscopy and infrared spectroscopy were used to quantify the MOPs loading in each composite. Electrochemical measurements of pristine materials and all PANI@MOP composites were conducted in acidic aqueous electrolytes to study the electrochemistry of both MOPs and PANI in the composites. Composites with the optimal capacitive performance in both series, PANI@SO₃-RuMOP (1:0.035) and PANI@t-Bu-RuMOP (1:0.07), achieve specific capacitances of 416 ± 37 F/g and 396 ± 34 F/g at 0.5 mA/cm², respectively. These capacitive performances significantly outperform the pristine PANI (347 ± 22 F/g). Both composites also exhibited better rate capability and higher long-term capacitance retention than pristine PANI. Findings here shed light on the use of redox-active MOPs as a minor additive during in situ polymerization to synthesize conducting polymers with enhanced capacitive performance for electrochemical energy storage devices.