S-doped Co(OH)2 ultrathin nanosheets hybridized with PANI as a binder-free electrode for supercapacitor and oxygen evolution reaction

초록

Anion-doped metal hydroxides exhibit excellent electrochemical properties, making them promising candidates for applications in energy storage and conversion technologies. In this work, we present a simple and costeffective synthesis of two-dimensional (2D), wrinkled, ultrathin nanosheets of sulfur-doped cobalt hydroxide hybridized with PANI (S-Co(OH)2/PANI) using an electrodeposition technique, and evaluate their supercapacitor and oxygen evolution reaction (OER) performance as binder-free electrodes. To understand the role of sulfur doping and PANI hybridization, a comparative study was conducted between S-doped and undoped Co(OH)2, as well as their respective PANI composites. Among these, the S-Co(OH)2/PANI hybrid demonstrated the best electrochemical performance, showing a high specific capacitance of 483.3 F g-1 at 1 A g-1 with 64.01 % capacity retention and 94.39 % coulombic efficiency after 2000 charge-discharge cycles. Furthermore, the asymmetric supercapacitor (ASC) device with S-Co(OH)2/PANI//KOH//AC configuration exhibited a capacitance of 50.43 F g-1 at 0.75 A g-1, retaining 62.68 % of its initial capacity and maintaining a coulombic efficiency of 70.84 % after 2000 cycles. The ASC device also delivered a high energy density of 56.73 Wh kg-1 at a power density of 2024.66 W kg-1. As an OER catalyst, the S-Co(OH)2/PANI hybrid showed a low overpotential of 221 mV at 10 mA cm-2, a favourable Tafel slope of 76 mV dec-1, and excellent 24 h stability. It reached a benchmark current density of 10 mA cm-2 at 1.451 V, outperforming the IrO2-based catalyst. These results demonstrate that sulfur doping and PANI hybridization synergistically enhance the electrochemical performance of Co(OH)2-based materials, offering a promising strategy for multifunctional energy applications.

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