3D printed C 3 N 4 -based structures for photo-, electro-chemical and piezoelectric applications †

In this study, we explored the use of two 3D printing techniques, direct ink writing (DIW) and digital light processing (DLP), as novel and flexible strategies to control the 3D geometry and morphology of functional materials. To demonstrate their potential, different types of carbon nitride (C₃N₄) were combined and successfully printed with various polymers, such as methylcellulose (MC) and polysulfone (PSF). C₃N₄ is a metal-free photoactive material, which has recently gained significant interest due to its attractive optoelectronic properties. The 3D printed C₃N₄-based composites were tested in typical potential applications for their photo-, piezo- and electrocatalytic activity. Tailored formulations and design strategies were devised for pollutant photo- and piezoelectric degradation as well as electrochemical sensing, showing the effect of the formulation on the performance of the 3D printed C₃N₄ polymer composites. The performance evaluations revealed promising results, complemented by the stability of the 3D printed geometries in organic solvents commonly used in chemical syntheses. Specifically, the DIW g-C₃N₄/PSF formulation showed the highest overall pollutant removal (71%), followed by the DLP g-C₃N₄-based formulations which showed high removal efficiencies (up to 63%) with a high level of piezoelectric degradation (up to 41%). In addition, Piezoresponse Force Microscopy (PFM) analysis of both the starting bulk g-C₃N₄ powder and DIW 3D printed bulk g-C₃N₄/MC composite revealed significant piezoelectric properties, broadening their potential applications.