3D Printing to enable photocatalytic process engineering: A critical assessment and perspective

3D printing (3DP) has emerged as a transformative technology for advancing the field of photocatalytic process engineering (PPE). In this systematic review, we explore recent developments in 3D-printed photocatalytic structures, immobilization techniques, and reactor design. Notably, 3DP offers innovative solutions to challenges in PPE, such as photocatalyst recovery, low surface area exposure to irradiation, and mass transfer limitations. We find that micro-structured photocatalytic reactors (PRs) have particularly benefited from 3DP, enabling diverse designs, shapes, and structures for pollutant degradation. Additionally, combining indirect plasma grafting with 3DP enhances photocatalytic structures, optimizing active sites, light absorption, and fluid dynamics. Smart design approaches involving CAD, Multiphysics CFD modeling, and 3DP integration ensure efficient resource deployment and optimized design. However, several challenges, including material limitations, scalability, and production times, must be addressed for large-scale PPE implementation. To harness the full potential of 3DP in photocatalysis, future efforts should focus on macro-photocatalytic structures and reactors, along with long-term performance assessment and durability studies.