Synergistic Charge Redistribution and Structural Evolution in Three-Dimensionally Printed Mn-Prussian Blue...

Three-dimensional (3D) printing offers a versatile route to fabricate multifunctional electrodes by integrating key components within a single structure. Herein, we developed polylactic acid/carbon black/reduced graphene oxide/manganese hexacyanoferrate (PLA/CB/rGO/MnHCF) electrodes and evaluated their structural and electrochemical behavior to understand the cooperative dynamics governing their performance. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed the homogeneous dispersion of MnHCF microcubes and carbonaceous additives within the PLA matrix. PLA/CB/rGO electrodes exhibited predominantly capacitive behavior, whereas MnHCF incorporation introduced distinct redox features associated with Fe^2+/3+ and Mn^2+/3+ transitions. Galvanostatic cycling revealed enhanced capacitance and high reversibility, with long-term testing over 3,500 cycles showing a remarkable increase in capacitance. Postcycling characterization indicated expansion of the electroactive surface area, activation of previously inaccessible MnHCF sites, and reduction of rGO/CB functional groups. Raman and FTIR analyses confirmed persistence of Mn³⁺ and Fe³⁺ centers after cycling. These findings support a cooperative mechanism in which the insulating PLA matrix imposes localized electron bottlenecks, redirecting the charge toward rGO/CB sites for reduction while sustaining MnHCF oxidation. This synergistic redistribution progressively enhances redox activity and conductivity, turning the PLA host's insulating nature into a driver of long-term activation. Overall, the 3D-printed PLA/CB/rGO/MnHCF electrodes demonstrate stability, progressive activation, and promise for scalable and tunable energy storage applications.