Unleashing potential of novel 2D-Bi2S3/1D-SnO2 heterostructure thin film anodes for light-fostered asymmetric electrochromic supercapacitors

Abstract

In this work, a novel 2D-Bi₂S₃/1D-SnO₂, n–n heterostructure thin film was employed as a pseudocapacitive photoanode for enhanced solar energy utilization, yielding a significant improvement in energy storage performance. The three-electrode system delivered an areal capacitance of 15.22 mF cm⁻² in 1 M Na₂SO₄ electrolyte at 0.2 mA cm⁻² under 1 sun illumination, achieving 33% enhancement compared to dark conditions. In addition, the fabricated Bi₂S₃/SnO₂‖PEDOT:PSS asymmetric photo-assisted electrochromic supercapacitor device exhibited a maximum areal capacitance of 1.78 mF cm⁻² at 0.06 mA cm⁻², which represents a 2.5-fold increase over its performance in the dark (0.70 mF cm⁻² at 0.06 mA cm⁻²). Under illumination, the device also showed an areal energy density (E_a) of 0.8 mWh cm⁻² and areal power density (P_a) of 356 mW cm⁻². The device retained excellent cycling stability, with capacitance retention of 82.2% and 77.2% at 0.2 mA cm⁻² after 1000 GCD cycles under dark and illumination, respectively. Mechanistic investigations revealed that the intercalation/de-intercalation of Na⁺ ions into 2D Bi₂S₃ (Bi₂S₃ + xNa⁺ + xe⁻ ↔ Na_xBi₂S₃) and SO₄²⁻ ions into the PEDOT:PSS chain during the charge–discharge process were facilitated by photon-induced redox activity and efficient charge separation by SnO₂ nanorods (NRs), thereby improving energy storage capability. This study underscores the potential of novel heterostructure design and material combinations for the development of next-generation photo-rechargeable supercapacitors, paving the way for self-powered electronic devices.