Multifunctional visual photoelectrochemical sensor based on ternary Sb2WO6/P@g-C3N4/Ag2S nanocomposite for selective mercury-ion monitoring in environmental matrices and energy storage applications

Abstract

This study presents the novel finding on a multifunctional Sb₂WO₆/P@g-C₃N₄/Ag₂S nanocomposite for both ultra-sensitive mercury detection and high-performance supercapacitor applications, synthesized via a scalable, eco-friendly process. In this study, metal tungstates were selected for their largely untapped potential, and their performance was improved via surface modifications and bandgap engineering. The composite was developed using P@g-C₃N₄ as a stable immobilization platform and Ag₂S, a I–IV semiconductor, to promote the formation of hybrid heterojunctions. These heterojunctions enhanced the optical properties and offered appropriate redox potentials. The proposed photoelectrochemical sensor effectively detected Hg^2 + in different water matrices, achieving a detection limit of 0.02 pM. The fabricated electrode exhibited excellent selectivity and strong reproducibility. Moreover, the asymmetric supercapacitor designed using the proposed nanocomposite exhibited a specific capacitance of 532.79 F/g at a current density of 1 A/g. This supercapacitor also demonstrated enhanced energy and power densities of 28.4 Wh/kg and 1733.73 W/kg, respectively, as well as a capacitive retention of 89.3 %. This novel ternary system offers a dual-functional platform with practical relevance in real-time mercury ion monitoring and sustainable energy storage, representing a significant step toward integrated environmental sensing and power solutions.