Recent Advances in Sustainable and Green Chemistry for Polyurethane-Based High-Performance Supercapacitor Electrodes

Abstract The increasing demand for sustainable energy storage solutions has intensified the focus on high-performance supercapacitors, known for their rapid charge/discharge capabilities, high power density, and long cycle life. Polyurethane (PU)-based materials have gained attention as promising candidates for supercapacitor electrodes, due to their flexibility, mechanical robustness, and tunable properties. It is important to clarify that PU typically does not contribute directly to charge storage via adsorption or pseudocapacitive mechanisms. Instead, PU serves as a flexible scaffold, a binder, or a precursor for the preparation of heteroatom-doped carbon materials upon thermal treatment. Thus, the term 'PU-based' in this review refers to PU-supported or PU-derived composites, where PU enables structural or functional integration of active electrode Materials. Polyurethane composites incorporating graphene oxide have demonstrated a specific capacitance of 758.8 mF/cm 2 with capacitance retention of 92% over 5,000 cycles. Other PU-based electrodes have achieved energy densities up to 22.5 Wh/kg and power densities of 1472.7 W/kg, reflecting their potential for high-performance energy storage applications. Despite these advantages, challenges, such as low intrinsic conductivity and the environmental impact of traditional synthesis methods, limit their widespread adoption. Conventional PU composites often incorporate conductive additives like carbon materials, metal oxides, or conductive polymers to enhance their electrochemical performance, yet these approaches may involve non-renewable or toxic components. Developing green energy materials that adhere to sustainability and green chemistry principles is crucial to address these limitations. This includes using renewable resources, environmentally friendly processing techniques, and recyclable materials to reduce the ecological footprint and meet the growing need for sustainable energy storage technologies. This review highlights current trends in developing eco-friendly supercapacitor materials, addressing key challenges such as limited conductivity and complex processing. It uniquely integrates green chemistry principles with advances in polyurethane composites, emphasizing sustainable feedstocks, heteroatom doping, and functional nanomaterials. By combining these aspects, this review provides a comprehensive perspective not fully covered in existing literature.