Nickel-Loaded 3D-Printed Electrode for In Situ Electrochemical Conversion to a Prussian Blue Analogue: Synthetic Parameter Optimization for Pseudocapacitor Applications.

Developing cost-effective and scalable energy storage devices is critical for advancing sustainable technologies. This study presents the fabrication of a novel 3D-printed PLA/Gr/NiHCF electrode, leveraging the benefits of additive manufacturing and a systematic factorial design of experiments (DOE) approach. The motivation stems from the need for simplified production methods that deliver high-performance materials while reducing waste and energy consumption. The electrode was synthesized through a two-step process involving 3D printing of a PLA/graphite/nickel acetate (PLA/Gr/Ni) composite followed by electrochemical conversion of nickel hexacyanoferrate (NiHCF) particles. The factorial DOE methodology optimized the composition of the PLA/Gr matrix and the electrochemical deposition conditions, ensuring a robust process with reproducible outcomes. The structural and electrochemical properties of the materials were evaluated using FTIR, Raman, SEM, EDS, CV, and EIS. The PLA/Gr/NiHCF electrode exhibited outstanding electrochemical performance, with a specific capacitance (C_s) of 37.33 mF cm^-2 at 0.1 mA cm^-2 in a three-electrode system, significantly outperforming the control PLA/Gr electrode (0.58 mF cm^-2). In a two-electrode symmetrical configuration, the system delivered a C_s of 40.4 mF cm^-2 at 0.1 mA cm^-2, with excellent retention (95% over 100 cycles) and reversible Coulombic efficiency (98.3%). The electrode's pseudocapacitive behavior, driven by the surface-confined redox activity of NiHCF, was confirmed through CV and EIS analyses. The results highlight the practicality of 3D printing combined with simple electrochemical modification for producing efficient supercapacitor electrodes. This study underscores the importance of factorial DOE in optimizing material properties and establishes the PLA/Gr/NiHCF electrode as a promising candidate for scalable, sustainable energy storage applications.