Synergistic effect of redox-active SrMnO3/g-C3N4 electrode materials for supercapattery hybrid energy storage devices and electrochemical sensing of hydroquinone

Transition-metal oxides are attracting significant interest as potential energy storage materials and electrochemical sensors for hydroquinone (HQ) detection due to their exceptional redox properties, electrochemical activity, and abundance of electroactive sites. However, their practical application is hindered by challenges such as limited electrochemical stability and electrical conductivity, which restrict their economic viability. A sensitive sensor is developed featuring 2D g-C₃N₄ nanosheet networks decorated with strontium manganite nanoparticles, referred to as SrMnO₃/g-C₃N₄, for applications in supercapacitors and electrochemical sensing. The designed hybrid-type devices exhibit a energy density of 84.8 Wh/kg and a power density of 1190.3 W/kg while maintaining robust stability over 10,000 cycles with a capacitive retention of 86 % and a coulombic efficiency of 95 %. Dunn's model clarifies the faradaic and non-faradic contributions in the fabricated device, demonstrating how its capacitive and diffusive contributions relate to the scan rate. The fabricated sensing device is used for the electrochemical detection of HQ. The SrMnO₃/g-C₃N₄-modified GCE demonstrates enhanced performance, with a low limit of detection (LOD) of 6.32 μM over a broad linear range of 1–600 μM. Furthermore, the SrMnO₃/g-C₃N₄-modified electrode shows high sensitivity, achieving a 0.214 μA μM⁻¹ cm⁻² value. The sensor proves its practicality and recovery performance through real sample wastewater and tap water analysis.