Hierarchical nanostructuring of PCN-222/NiSe₂@PANI composites for enhanced electrochemical performance in supercapattery and hydrogen evolution reaction applications

The supercapattery integrates the rapid power output of supercapacitors (SCs) with the substantial energy storage capacity typical of batteries. Metal-organic frameworks (MOFs) offer a stable porous structure that enhances efficient ion transport through strong metal-organic linkages. Metal diselenides contribute high conductivity and stability, strengthening the composite’s energy and power densities. Polyaniline (PANI) provides pseudocapacitive behavior, further improving charge storage. This study presents a PCN-222/NiSe₂@PANI composite synthesized hydrothermal, ensuring strong material integration and uniform distribution. Surface morphology and phase purity, analyzed by SEM and XRD, confirmed structural uniformity and stability. Electrochemical testing revealed a specific capacity (Qs) of 2449 ± 5 C/g at 2.0 A/g in a tri-electrode configuration. A two-electrode supercapattery, fabricated using PCN-222/NiSe₂@PANI as the anode and activated carbon (AC) as the cathode, achieved an energy density of 68 Wh/kg and a power density of 900 W/kg, with 87.6% capacity retention over 8,000 GCD cycles, surpassing standard benchmarks. The power-law analysis yielded b-fitting values between 0.58 and 0.75, indicating hybrid charge storage. The composite exhibited promising hydrogen evolution reaction (HER) activity, with an overpotential of 87 ± 5 mV and a Tafel slope of 78 ± 5 mV/dec, showing high catalytic efficiency and favorable charge transfer kinetics. These results position PCN-222/NiSe₂@PANI as a strong contender for high-performance supercapattery applications, advancing energy storage and conversion technologies.