Invasive plants Spartina alterniflora-derived carbon quantum dots/copper-manganese phosphates for supercapacitor electrodes

Spartina alterniflora, an invasive plant species, has caused significant ecological damage to coastal ecosystems. Traditional physical management methods generate substantial biomass waste, potentially leading to secondary environmental pollution. To address this, we propose a sustainable strategy to convert Spartina alterniflora into high-value carbon materials, mitigating environmental harm while enhancing the electrochemical performance of supercapacitor electrodes. Bimetallic phosphates, despite their high energy storage potential, face challenges such as large volume changes during cycling and poor kinetic performance. Carbon quantum dots, derived from Spartina alterniflora, offer advantages such as nanoscale dimensions, excellent photoelectric properties, high stability, and environmental compatibility, effectively addressing these limitations. The CMPCD-2 (Copper-manganese bimetallic phosphates doped with 2 mg of carbon quantum dots) composite demonstrated a specific capacitance of 277 F/g at 0.5 A/g. An asymmetric supercapacitor (ASC) device, constructed with the CMPCD-2 electrode as the positive electrode and activated carbon as the negative electrode, achieved an energy density of 17.8 Wh kg^-1 at a power density of 2.1 kW kg^-1. This work not only advances the development of bimetallic phosphate-based materials for energy storage but also provides a sustainable solution for the effective utilization of Spartina alterniflora, bridging ecological restoration and energy storage technology.