This study successfully demonstrates the remarkable performance of size-tuned phosphorene quantum dots (PQDs) for Na-ion batteries. Through a controlled electrochemical exfoliation approach, PQDs of varying sizes are produced, enabling the investigation of size-dependent properties critical to energy storage. The incorporation of Prussian white (PW) as a composite with PQDs (PQD_PW) further enhances their electrochemical performance, providing a synergistic effect that improved charge transfer kinetics, structural stability, and overall cycling performance.