2D SprayPath: An Open-Source Tool for Automated Spray-Coating of Gas Diffusion Electrodes for CO₂ Electroreduction

The fabrication of gas diffusion electrodes (GDEs) by spray coating is widely employed in CO₂ electroreduction research due to its simplicity, scalability, and ability to produce catalyst layers with controlled loadings. However, achieving reproducible deposition patterns remains challenging because of the large number of operational parameters involved and the limited availability of dedicated open-source tools for trajectory planning and process automation. In this work, we present 2D SprayPath, an open-source software developed to generate parameterized planar deposition trajectories and corresponding G-code instructions for automated spray-coating systems. The software enables users to define key deposition parameters, including scan area dimensions, line spacing, nozzle height, spray width, scanning velocity, and number of repetitions, while providing real-time visualization of the planned trajectories. The generated G-code can be directly executed by motion-control systems based on standard CNC or modified 3D-printer platforms. Experimental validation was performed using a low-cost spray coater adapted from an Ender-3 Pro 3D printer. Two distinct deposition configurations were evaluated to compare nominal and experimentally measured dimensions. The results demonstrated excellent agreement between programmed and deposited patterns, with relative errors below 1% for most geometric parameters and a maximum deviation of approximately 1.5% for line spacing. The spray width remained stable across all experiments, confirming the reliability of the deposition process and the fidelity of the generated trajectories. The results demonstrate that 2D SprayPath provides an accurate, reproducible, and accessible solution for automated spray coating. Although motivated by the fabrication of GDEs for CO₂ electroreduction, the software can be extended to other applications involving controlled planar motion, including thin-film deposition, substrate scanning, and laboratory automation. To promote reproducibility and collaborative development, the source code has been made freely available through the open-source GitHub repository PauloFalsetti/2D_SprayPath.